C. Barbieri

Search for another author

Author Description

Ask a Question About This Mathematician

Self-consistent Green's function method for nuclei and nuclear matter

2004-04-01

W. H. Dickhoff , C. Barbieri

View PDF Chat

Chiral two- and three-nucleon forces along medium-mass isotope chains

2014-06-05

V. Somà , Andrea Cipollone , C. Barbieri +2 more

Three-nucleon forces (3NFs), and in particular terms of the Fujita-Miyazawa type, strongly influence the structure of neutron-rich exotic isotopes. Ab-initio calculations have shown that chiral two- and three-nucleon interactions correctly … Three-nucleon forces (3NFs), and in particular terms of the Fujita-Miyazawa type, strongly influence the structure of neutron-rich exotic isotopes. Ab-initio calculations have shown that chiral two- and three-nucleon interactions correctly reproduce binding energy systematics and neutron driplines of oxygen and nearby isotopes. Exploiting the novel self-consistent Gorkov-Green's function approach, we present the first investigation of Ar, K, Ca, Sc and Ti isotopic chains. Leading chiral 3N interactions are mandatory to reproduce the trend of binding energies throughout these chains and to obtain a good description of two-neutron separation energies. At the same time, nuclei in this mass region are systematically overbound by about 40 MeV and the $N=20$ magic gap is significantly overestimated. We conclude that ab-initio many-body calculations of mid-mass isotopic chains challenge modern theories of elementary nuclear interactions.

View PDF Chat

Isotopic Chains Around Oxygen from Evolved Chiral Two- and Three-Nucleon Interactions

2013-08-07

Andrea Cipollone , C. Barbieri , P. Navrátil

We extend the formalism of self-consistent Green's function theory to include three-body interactions and apply it to isotopic chains around oxygen for the first time. The third-order algebraic diagrammatic construction … We extend the formalism of self-consistent Green's function theory to include three-body interactions and apply it to isotopic chains around oxygen for the first time. The third-order algebraic diagrammatic construction [ADC(3)] equations for two-body Hamiltonians can be exploited upon defining system-dependent one- and two-body interactions coming from the three-body force, and correspondingly dropping interaction reducible diagrams. This goes beyond the standard normal ordering truncations recently used in ab-inito studies. The Koltun sum rule for the total binding energy acquires a correction due to the added three-body interaction. This formalism is then applied to study chiral two-nucleon (2N) and three-nucleon forces (3NF) evolved to low momentum cutoffs. We find that these interactions reproduce the binding energies of nitrogen, oxygen and fluorine isotopes to great accuracy, providing clear indication of the predictive power of this approach. All three neutron driplines are correctly predicted when full 3NF are included. The formalism introduced also allows to calculate form factors for nucleon transfer on doubly magic systems.

View PDF Chat

Novel chiral Hamiltonian and observables in light and medium-mass nuclei

2020-01-22

V. Somà , P. Navrátil , Francesco Raimondi +2 more

Background: Recent advances in nuclear structure theory have led to the availability of several complementary ab initio many-body techniques applicable to light and medium-mass nuclei as well as nuclear matter. … Background: Recent advances in nuclear structure theory have led to the availability of several complementary ab initio many-body techniques applicable to light and medium-mass nuclei as well as nuclear matter. After successful benchmarks of different approaches, the focus is moving to the development of improved models of nuclear Hamiltonians, currently representing the largest source of uncertainty in ab initio calculations of nuclear systems. In particular, none of the existing two- plus three-body interactions is capable of satisfactorily reproducing all the observables of interest in medium-mass nuclei.Purpose: A novel parametrization of a Hamiltonian based on chiral effective field theory is introduced. Specifically, three-nucleon operators at next-to-next-to-leading order are combined with an existing (and successful) two-body interaction containing terms up to next-to-next-to-next-to-leading order. The resulting potential is labeled $NN+3N\text{(lnl)}$. The objective of the present work is to investigate the performance of this new Hamiltonian across light and medium-mass nuclei.Methods: Binding energies, nuclear radii, and excitation spectra are computed using state-of-the-art no-core shell model and self-consistent Green's function approaches. Calculations with $NN+3N\text{(lnl)}$ are compared to two other representative Hamiltonians currently in use, namely ${\mathrm{NNLO}}_{\text{sat}}$ and the older $NN+3N(400)$.Results: Overall, the performance of the novel $NN+3N\text{(lnl)}$ interaction is very encouraging. In light nuclei, total energies are generally in good agreement with experimental data. Known spectra are also well reproduced with a few notable exceptions. The good description of ground-state energies carries on to heavier nuclei, all the way from oxygen to nickel isotopes. Except for those involving excitation processes across the $N=20$ gap, which is overestimated by the new interaction, spectra are of very good quality, in general superior to those obtained with ${\mathrm{NNLO}}_{\text{sat}}$. Although largely improving on $NN+3N(400)$ results, charge radii calculated with $NN+3N\text{(lnl)}$ still underestimate experimental values, as opposed to the ones computed with ${\mathrm{NNLO}}_{\text{sat}}$ that successfully reproduce available data on nickel.Conclusions: The new two- plus three-nucleon Hamiltonian introduced in the present work represents a promising alternative to existing nuclear interactions. In particular, it has the favorable features of (i) being adjusted solely on $A=2,3,4$ systems, thus complying with the ab initio strategy, (ii) yielding an excellent reproduction of experimental energies all the way from light to medium-heavy nuclei, and (iii) behaving well under similarity renormalization group transformations, with negligible four-nucleon forces being induced, thus allowing large-scale calculations up to medium-heavy systems. The problem of the underestimation of nuclear radii persists and will necessitate novel developments.

View PDF Chat

Ab initioGorkov-Green's function calculations of open-shell nuclei

2013-01-24

V. Somà , C. Barbieri , T. Duguet

We present results from a new ab-initio method that uses the self-consistent Gorkov Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to … We present results from a new ab-initio method that uses the self-consistent Gorkov Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to second order and is implemented here in nuclei for the first time on the basis of realistic nuclear forces. We find good convergence of the results with respect to the basis size in Ca44 and Ni74 and discuss quantities of experimental interest including ground-state energies, pairing gaps and particle addition/removal spectroscopy. These results demonstrate that the Gorkov method is a valid alternative to multireference approaches for tackling degenerate or near degenerate quantum systems. In particular, it increases the number of mid-mass nuclei accessible in an ab-initio fashion from a few tens to a few hundreds.

View PDF Chat

Self-consistent Green's functions formalism with three-body interactions

2013-11-27

Arianna Carbone , Andrea Cipollone , C. Barbieri +2 more

We extend the self-consistent Green's functions formalism to take into account three-body interactions. We analyze the perturbative expansion in terms of Feynman diagrams and define effective one- and two-body interactions, … We extend the self-consistent Green's functions formalism to take into account three-body interactions. We analyze the perturbative expansion in terms of Feynman diagrams and define effective one- and two-body interactions, which allows for a substantial reduction of the number of diagrams. The procedure can be taken as a generalization of the normal ordering of the Hamiltonian to fully correlated density matrices. We give examples up to third order in perturbation theory. To define nonperturbative approximations, we extend the equation-of-motion method in the presence of three-body interactions. We propose schemes that can provide nonperturbative resummation of three-body interactions. We also discuss two different extensions of the Koltun sum rule to compute the ground state of a many-body system.

View PDF Chat

Ab initioself-consistent Gorkov-Green's function calculations of semimagic nuclei: Formalism at second order with a two-nucleon interaction

2011-12-19

V. Somà , T. Duguet , C. Barbieri

An ab initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly magic and semimagic nuclei … An ab initio calculation scheme for finite nuclei based on self-consistent Green's functions in the Gorkov formalism is developed. It aims at describing properties of doubly magic and semimagic nuclei employing state-of-the-art microscopic nuclear interactions and explicitly treating pairing correlations through the breaking of U(1) symmetry associated with particle number conservation. The present paper introduces the formalism necessary to undertake applications at (self-consistent) second order using two-nucleon interactions in a detailed and self-contained fashion. First applications of such a scheme will be reported soon in a forthcoming publication. Future works will extend the present scheme to include three-nucleon interactions and implement more advanced truncation schemes.

View PDF Chat

Radii and Binding Energies in Oxygen Isotopes: A Challenge for Nuclear Forces

2016-07-27

V. Lapoux , V. Somà , C. Barbieri +3 more

$A\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations using elastic scattering data on oxygen are able to accurately reproduce the isotopes' binding energies but fail to describe the charge and matter radii of the most … $A\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations using elastic scattering data on oxygen are able to accurately reproduce the isotopes' binding energies but fail to describe the charge and matter radii of the most neutron-rich systems.

View PDF Chat

Probing the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:math>Shell Closure below the Magic Proton Number<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi><mml:mo>=</mml:mo><mml:mn>20</mml:mn></mml:mrow></mml:math>: Mass Measurements of the Exotic Isotopes<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts…

2015-05-20

M. Rosenbusch , P. Ascher , D. Atanasov +7 more

The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic … The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly lower than for 52Ca, highlighting the doubly-magic nature of this nuclide. Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.

View PDF Chat

Dawning of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:math> Shell Closure Seen through Precision Mass Measurements of Neutron-Rich Titanium Isotopes

2018-02-09

E. Leistenschneider , M. P. Reiter , Samuel Ayet San Andrés +7 more

A precision mass investigation of the neutron-rich titanium isotopes $^{51\ensuremath{-}55}\mathrm{Ti}$ was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N=32$ … A precision mass investigation of the neutron-rich titanium isotopes $^{51\ensuremath{-}55}\mathrm{Ti}$ was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N=32$ shell closure, and the overall uncertainties of the $^{52\ensuremath{-}55}\mathrm{Ti}$ mass values were significantly reduced. Our results conclusively establish the existence of the weak shell effect at $N=32$, narrowing down the abrupt onset of this shell closure. Our data were compared with state-of-the-art ab initio shell model calculations which, despite very successfully describing where the $N=32$ shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned multiple-reflection time-of-flight mass spectrometer, substantiated by independent measurements from TITAN's Penning trap mass spectrometer.

View PDF Chat

Role of Long-Range Correlations in the Quenching of Spectroscopic Factors

2009-11-09

C. Barbieri

We consider the proton and neutron quasiparticle orbits around the closed-shell $^{56}\mathrm{Ni}$ and $^{48}\mathrm{Ca}$ isotopes. It is found that large model spaces (beyond the capability of shell model applications) are … We consider the proton and neutron quasiparticle orbits around the closed-shell $^{56}\mathrm{Ni}$ and $^{48}\mathrm{Ca}$ isotopes. It is found that large model spaces (beyond the capability of shell model applications) are necessary for predicting the quenching of spectroscopic factors. The particle-vibration coupling is identified as the principal mechanism. Additional correlations---due to configuration with several particle-hole excitations---are estimated using shell model calculations and generate an extra reduction which is $\ensuremath{\lesssim}4%$ for most quasiparticle states. The theoretical calculations nicely agree with ($e$, ${e}^{\ensuremath{'}}p$) and inverse kinematics knockout experiments. These results open a new path for a microscopic understanding of the shell model.

View PDF Chat

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

2015-07-10

Andrea Cipollone , C. Barbieri , P. Navrátil

The impact of three-nucleon forces (3NFs) along the oxygen chain is investigated for the spectral distribution for attachment and removal of a nucleon, spectroscopic factors and matter radii. We employ … The impact of three-nucleon forces (3NFs) along the oxygen chain is investigated for the spectral distribution for attachment and removal of a nucleon, spectroscopic factors and matter radii. We employ self-consistent Green's function (SCGF) theory which allows a comprehensive calculation of the single particle spectral function. For the closed subshell isotopes, $^{14}$O, $^{16}$O, $^{22}$O, $^{24}$O and $^{28}$O, we perform calculations with the Dyson-ADC(3) method. The remaining open shell isotopes are studied using the newly developed Gorkov-SCGF formalism up to second order. We produce plots for the full-fledged spectral distributions. The spectroscopic factors for the dominant quasiparticle peaks are found to depend very little on the leading order (NNLO) chiral 3NFs. The latters have small impact on the calculated matter radii, which, however are consistently obtained smaller than experiment. Similarly, single particle spectra tend to be diluted with respect to experiment. This effect might hinder, to some extent, the onset of correlations and screen the quenching of calculated spectroscopic factors. The most important effects of 3NFs is thus the fine tuning of the energies for the dominant quasiparticle states, which govern the shell evolution and the position of driplines. Although present chiral NNLO 3NFs interactions do reproduce the binding energies correctly in this mass region, the details of the nuclear wave function remain at odd with the experiment showing too small radii and a too dilute single particle spectrum, similar to what already pointed out for larger masses. This suggests a lack of repulsion in the present model of NN+3N interactions which is mildly apparent already for masses in the A=14--28 range.

View PDF Chat

Optimization of anemia treatment in hemodialysis patients via reinforcement learning

2014-07-19

Pablo Escandell-Montero , Milena Chermisi , José M. Martínez-Martínez +7 more

View PDF Chat

Ab initioself-consistent Gorkov-Green's function calculations of semi-magic nuclei: Numerical implementation at second order with a two-nucleon interaction

2014-02-28

V. Somà , C. Barbieri , T. Duguet

Background: The newly developed self-consistent Gorkov-Green's function approach represents a promising path to the ab initio description of mid-mass open-shell nuclei. The formalism based on a two-nucleon interaction and the … Background: The newly developed self-consistent Gorkov-Green's function approach represents a promising path to the ab initio description of mid-mass open-shell nuclei. The formalism based on a two-nucleon interaction and the second-order truncation of Gorkov's self-energy has been described in detail in Ref. [Som\`a, Duguet, and Barbieri, Phys. Rev. C 84, 064317 (2011)].Purpose: The objective is to discuss the methodology used to solve Gorkov's equation numerically and to gauge its performance in view of carrying out systematic calculations of medium-mass nuclei in the future. In doing so, different sources of theoretical error and degrees of self-consistency are investigated.Methods: We employ Krylov projection techniques with a multi-pivot Lanczos algorithm to efficiently handle the growth of poles in the one-body Green's function that arises as a result of solving Gorkov's equation self-consistently. We first characterize the numerical scaling of Gorkov's calculations based on full self-consistency and on a partially self-consistent scheme coined as ``sc0''. Using small model spaces, the Krylov projection technique is then benchmarked against exact diagonalization of the original Gorkov matrix. Next, the convergence of the results as a function of the number ${N}_{\ensuremath{\ell}}$ of Lanczos iterations per pivot is investigated in large model spaces. Eventually, the convergence of the calculations with the size of the harmonic oscillator model space is examined.Results: Gorkov self-consistent Green's function (SCGF) calculations performed on the basis of Krylov projection techniques display a favorable numerical scaling that authorizes systematic calculations of mid-mass nuclei. The Krylov projection selects efficiently the appropriate degrees of freedom while spanning a very small fraction of the original space. For typical large-scale calculations of mid-mass nuclei, a Krylov projection making use of ${N}_{\ensuremath{\ell}}\ensuremath{\approx}50$ yields a sufficient degree of accuracy on the observables of interest. The partially self-consistent sc0 scheme is shown to reproduce fully self-consistent solutions in small model spaces at the 1$%$ level. Eventually, Gorkov-Green's function calculations performed on the basis of SRG-evolved interactions show a fast convergence as a function of the model-space size.Conclusions: The end result is a tractable, accurate and gently scaling ab initio scheme applicable to complete isotopic and isotonic chains in the medium-mass region. The partially self-consistent sc0 scheme provides an excellent compromise between accuracy and computational feasibility and will be the workhorse of systematic Gorkov-Green's function calculations in the future. The numerical scaling and performances of the algorithm employed offers the possibility (i) to apply the method to even heavier systems than those (e.g., ${}^{74}$Ni) already studied so far and (ii) to perform converged Gorkov SCGF calculations based on harder, e.g. original chiral interactions.

View PDF Chat

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

2019-08-26

A. Idini , C. Barbieri , P. Navrátil

We derive ab initio optical potentials from self-consistent Green's function theory and compute the elastic scattering of neutrons off oxygen and calcium isotopes. The comparison with scattering data is satisfactory … We derive ab initio optical potentials from self-consistent Green's function theory and compute the elastic scattering of neutrons off oxygen and calcium isotopes. The comparison with scattering data is satisfactory at low scattering energies. The method is benchmarked against the no-core shell model with continuum calculations, showing that virtual excitations of the target are crucial to predict proper fragmentation and absorption at higher energies. This is a significant step toward deriving optical potentials for medium mass nuclei and complex many-body systems in general.

View PDF Chat

Ab initio calculation of the potential bubble nucleus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi mathvariant="normal">Si</mml:mi><mml:mprescripts /><mml:none /><mml:mn>34</mml:mn></mml:mmultiscripts></mml:math>

2017-03-23

T. Duguet , V. Somà , S. Lecluse +2 more

The possibility that an unconventional depletion in the center of the charge density distribution of certain nuclei occurs due to a purely quantum mechanical effect has attracted theoretical and experimental … The possibility that an unconventional depletion in the center of the charge density distribution of certain nuclei occurs due to a purely quantum mechanical effect has attracted theoretical and experimental attention in recent years. We report on ab initio self-consistent Green's function calculations of one of such candidates, $^{34}$Si, together with its Z+2 neighbour $^{36}$S. Binding energies, rms radii and density distributions of the two nuclei as well as low-lying spectroscopy of $^{35}$Si, $^{37}$S, $^{33}$Al and $^{35}$P are discussed. The interpretation of one-nucleon removal and addition spectra in terms of the evolution of the underlying shell structure is also provided. The study is repeated using several chiral effective field theory Hamiltonians as a way to test the robustness of the results with respect to input inter-nucleon interactions. The prediction regarding the (non-)existence of the bubble structure in $^{34}$Si varies significantly with the nuclear Hamiltonian used. However, demanding that the experimental charge density distribution and the root mean square radius of $^{36}$S are well reproduced, along with $^{34}$Si and $^{36}$S binding energies, only leaves the NNLO$_{\text{sat}}$ Hamiltonian as a serious candidate to perform this prediction. In this context, a bubble structure, whose fingerprint should be visible in an electron scattering experiment of $^{34}$Si, is predicted. Furthermore, a clear correlation is established between the occurrence of the bubble structure and the weakening of the 1/2$^-$-3/2$^-$ splitting in the spectrum of $^{35}$Si as compared to $^{37}$S.

View PDF Chat

Neutrino-nucleus cross section within the extended factorization scheme

2019-02-11

Noemi Rocco , C. Barbieri , Omar Benhar +2 more

The factorization scheme, based on the impulse approximation and the spectral function formalism, has been recently generalized to allow the description of electromagnetic nuclear interactions driven by two-nucleon currents. We … The factorization scheme, based on the impulse approximation and the spectral function formalism, has been recently generalized to allow the description of electromagnetic nuclear interactions driven by two-nucleon currents. We have extended this framework to the case of weak charged and neutral currents and carried out calculations of the double-differential neutrino-carbon and neutrino-oxygen cross sections using two different models of the target spectral functions. The results, showing a moderate dependence on the input spectral function, confirm that our approach provides a consistent treatment of all reaction mechanisms contributing to the signals detected by accelerator-based neutrino experiments.

View PDF Chat

Quasiparticle and quasihole states of nuclei around<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Ni</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>56</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>

2009-06-15

C. Barbieri , M. Hjorth‐Jensen

The single-particle spectral function of $^{56}\mathrm{Ni}$ has been computed within the framework of self-consistent Green's functions theory. The Faddeev random phase approximation method and the $G$ matrix technique are used … The single-particle spectral function of $^{56}\mathrm{Ni}$ has been computed within the framework of self-consistent Green's functions theory. The Faddeev random phase approximation method and the $G$ matrix technique are used to account for the effects of long- and short-range physics on the spectral distribution. Large-scale calculations have been performed in spaces including up to ten oscillator shells. The chiral ${\mathrm{N}}^{3}\mathrm{LO}$ interaction is used together with a monopole correction that accounts for eventual missing three-nucleon forces. The single-particle energies associated with nucleon transfer to valence $1p0f$ orbits are found to be almost converged with respect to both the size of the model space and the oscillator frequency. The results support that $^{56}\mathrm{Ni}$ is a good doubly magic nucleus. The absolute spectroscopic factors to the valence states on $A=55,57$ are also obtained. For the transition between the ground states of $^{57}\mathrm{Ni}$ and $^{56}\mathrm{Ni}$, the calculations nicely agree with heavy-ion knockout experiments.

View PDF Chat

Faddeev description of two-hole–one-particle motion and the single-particle spectral function

2001-02-20

C. Barbieri , W. H. Dickhoff

The Faddeev technique is employed to address the problem of describing the influence of both particle-particle and particle-hole phonons on the single-particle self-energy. The scope of the few-body Faddeev equations … The Faddeev technique is employed to address the problem of describing the influence of both particle-particle and particle-hole phonons on the single-particle self-energy. The scope of the few-body Faddeev equations is extended to describe the motion of two-hole one-particle (two-particle one-hole) excitations. This formalism allows to sum both particle-particle and particle-hole phonons, obtained separately in the Random Phase Approximation. The appearance of spurious solutions for the present application of the Faddeev method is related to the inclusion of a consistent set of diagrams. The formalism presented here appears practical for finite nuclei and achieves a simultaneous inclusion of particle-particle and particle-hole phonons to all orders while the spurious solutions are properly eliminated.

View PDF Chat

Microscopic self-energy calculations and dispersive optical-model potentials

2011-09-29

S. J. Waldecker , C. Barbieri , W. H. Dickhoff

Nucleon self-energies for ${}^{40,48,60}$Ca isotopes are generated with the microscopic Faddeev-random-phase approximation (FRPA). These self-energies are compared with potentials from the dispersive optical model (DOM) that were obtained from fitting … Nucleon self-energies for ${}^{40,48,60}$Ca isotopes are generated with the microscopic Faddeev-random-phase approximation (FRPA). These self-energies are compared with potentials from the dispersive optical model (DOM) that were obtained from fitting elastic-scattering and bound-state data for ${}^{40,48}$Ca. The ab initio FRPA is capable of explaining many features of the empirical DOM potentials including their nucleon asymmetry dependence. The comparison furthermore provides several suggestions to improve the functional form of the DOM potentials, including among others the exploration of parity and angular momentum dependence. The nonlocality of the FRPA imaginary self-energy, illustrated by a substantial orbital angular momentum dependence, suggests that future DOM fits should consider this feature explicitly. The roles of the nucleon-nucleon tensor force and charge-exchange component in generating the asymmetry dependence of the FRPA self-energies are explored. The global features of the FRPA self-energies are not strongly dependent on the choice of realistic nucleon-nucleon interactions.

View PDF Chat

Faddeev treatment of long-range correlations and the one-hole spectral function of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>16</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:math>

2002-06-03

C. Barbieri , W. H. Dickhoff

The Faddeev technique is employed to study the influence of both particle-particle and particle-hole phonons on the one-hole spectral function of ${}^{16}\mathrm{O}.$ Collective excitations are accounted for at a random … The Faddeev technique is employed to study the influence of both particle-particle and particle-hole phonons on the one-hole spectral function of ${}^{16}\mathrm{O}.$ Collective excitations are accounted for at a random phase approximation level and subsequently summed to all orders by the Faddeev equations to obtain the nucleon self-energy. An iterative procedure is applied to investigate the effects of the self-consistent inclusion of the fragmentation in the determination of the phonons and the corresponding self-energy. The present results indicate that the characteristics of hole fragmentation are related to the low-lying states of ${}^{16}\mathrm{O}.$

View PDF Chat

Ab Initio Computation of Charge Densities for Sn and Xe Isotopes

2020-10-28

P. Arthuis , C. Barbieri , Matteo Vorabbi +1 more

We present the first ab initio calculations for open-shell nuclei past the tin isotopic line, focusing on Xe isotopes as well as doubly magic Sn isotopes. We show that, even … We present the first ab initio calculations for open-shell nuclei past the tin isotopic line, focusing on Xe isotopes as well as doubly magic Sn isotopes. We show that, even for moderately hard interactions, it is possible to obtain meaningful predictions and that the NNLO_{sat} chiral interaction predicts radii and charge density distributions close to the experiment. We then make a new prediction for ^{100}Sn. This paves the way for ab initio studies of exotic charge density distributions at the limit of the present ab initio mass domain, where experimental data is becoming available. The present study closes the gap between the largest isotopes reachable by ab initio methods and the smallest exotic nuclei accessible to electron scattering experiments.

View PDF Chat

Nuclear Charge Radii of the Nickel Isotopes <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ni</mml:mi></mml:mrow><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>58</mml:mn><mml:mo>−</mml:mo><mml:mn>68</mml:mn><mml:mo>,</mml:mo><mml:mn>70</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>

2022-01-14

S. Malbrunot-Ettenauer , S. Kaufmann , Sonia Bacca +7 more

Collinear laser spectroscopy is performed on the nickel isotopes ^{58-68,70}Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii R_{c} are extracted and compared to … Collinear laser spectroscopy is performed on the nickel isotopes ^{58-68,70}Ni, using a time-resolved photon counting system. From the measured isotope shifts, nuclear charge radii R_{c} are extracted and compared to theoretical results. Three ab initio approaches all employ, among others, the chiral interaction NNLO_{sat}, which allows an assessment of their accuracy. We find agreement with experiment in differential radii δ⟨r_{c}^{2}⟩ for all employed ab initio methods and interactions, while the absolute radii are consistent with data only for NNLO_{sat}. Within nuclear density functional theory, the Skyrme functional SV-min matches experiment more closely than the Fayans functional Fy(Δr,HFB).

View PDF Chat

Quasiparticles in neon using the Faddeev random-phase approximation

2007-11-06

C. Barbieri , Dimitri Van Neck , W. H. Dickhoff

The spectral function of the closed-shell neon atom is computed by expanding the electron self-energy through a set of Faddeev equations. This method describes the coupling of single-particle degrees of … The spectral function of the closed-shell neon atom is computed by expanding the electron self-energy through a set of Faddeev equations. This method describes the coupling of single-particle degrees of freedom with correlated two-electron, two-hole, and electron-hole pairs. The excitation spectra are obtained using the random-phase approximation (RPA), rather than the Tamm-Dancoff framework employed in the third-order algebraic diagrammatic construction method. The difference between these two approaches is studied, as well as the interplay between ladder and ring diagrams in the self-energy. Satisfactory results are obtained for the ionization energies as well as the energy of the ground state with the Faddeev RPA scheme, which is also appropriate for the high-density electron gas.

View PDF Chat

Shell structure of potassium isotopes deduced from their magnetic moments

2014-09-29

J. Papuga , M. L. Bissell , K. Kreim +7 more

\item[Background] Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \item[Purpose] Extend … \item[Background] Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \item[Purpose] Extend our knowledge about the evolution of the $1/2^+$ and $3/2^+$ states for K isotopes beyond the $N = 28$ shell gap. \item[Method] High-resolution collinear laser spectroscopy on bunched atomic beams. \item[Results] From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N = 19$ up to $N = 32$. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton $1d_{3/2}$ and $2s_{1/2}$ in the shell model and {\it{ab initio}} framework is also presented. \item[Conclusions] The dominant component of the wave function for the odd-$A$ isotopes up to $^{45}$K is a $\pi 1d_{3/2}^{-1}$ hole. For $^{47,49}$K, the main component originates from a $\pi 2s_{1/2}^{-1}$ hole configuration and it inverts back to the $\pi 1d_{3/2}^{-1}$ in $^{51}$K. For all even-$A$ isotopes, the dominant configuration arises from a $\pi 1d_{3/2}^{-1}$ hole coupled to a neutron in the $\nu 1f_{7/2}$ or $\nu 2p_{3/2}$ orbitals. Only for $^{48}$K, a significant amount of mixing with $\pi 2s_{1/2}^{-1} \otimes \nu (pf)$ is observed leading to a $I^{\pi}=1^{-}$ ground state. For $^{50}$K, the ground-state spin-parity is $0^-$ with leading configuration $\pi 1d_{3/2}^{-1} \otimes \nu 2p_{3/2}^{-1}$.

View PDF Chat

Self-Consistent Green’s Function Approaches

2017-01-01

C. Barbieri , Arianna Carbone

View PDF Chat

Nucleon-nucleus optical potential in the particle-hole approach

2005-07-29

C. Barbieri , B.K. Jennings

Feshbach's projection formalism in the particle-hole model space leads to a microscopic description of scattering in terms of the many-body self-energy. To investigate the feasibility of this approach, an optical … Feshbach's projection formalism in the particle-hole model space leads to a microscopic description of scattering in terms of the many-body self-energy. To investigate the feasibility of this approach, an optical potential for $^{16}\mathrm{O}$ is constructed starting from two previous calculations of the self-energy for this nucleus. The results reproduce the background phase shifts for positive parity waves and the resonances beyond the mean field. The latter can be computed microscopically for energies of astrophysical interest using Green's function theory.

View PDF Chat

Moving away from singly-magic nuclei with Gorkov Green’s function theory

2021-04-01

V. Somà , C. Barbieri , T. Duguet +1 more

View PDF Chat

Optical potentials for the rare-isotope beam era

2023-03-10

C. Hebborn , F. M. Nunes , G. Potel +7 more

Abstract We review recent progress and motivate the need for further developments in nuclear optical potentials that are widely used in the theoretical analysis of nucleon elastic scattering and reaction … Abstract We review recent progress and motivate the need for further developments in nuclear optical potentials that are widely used in the theoretical analysis of nucleon elastic scattering and reaction cross sections. In regions of the nuclear chart away from stability, which represent a frontier in nuclear science over the coming decade and which will be probed at new rare-isotope beam facilities worldwide, there is a targeted need to quantify and reduce theoretical reaction model uncertainties, especially with respect to nuclear optical potentials. We first describe the primary physics motivations for an improved description of nuclear reactions involving short-lived isotopes, focusing on its benefits for fundamental science discoveries and applications to medicine, energy, and security. We then outline the various methods in use today to build optical potentials starting from phenomenological, microscopic, and ab initio methods, highlighting in particular, the strengths and weaknesses of each approach. We then discuss publicly-available tools and resources facilitating the propagation of recent progresses in the field to practitioners. Finally, we provide a set of open challenges and recommendations for the field to advance the fundamental science goals of nuclear reaction studies in the rare-isotope beam era. This paper is the outcome of the Facility for Rare Isotope Beams Theory Alliance (FRIB-TA) topical program ‘Optical Potentials in Nuclear Physics’ held in March 2022 at FRIB. Its content is non-exhaustive, was chosen by the participants and reflects their efforts related to optical potentials.

View PDF Chat

Lepton scattering from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ar</mml:mi><mml:mprescripts/><mml:none/><mml:mn>40</mml:mn></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ti</mml:mi><mml:mprescripts/><mml:none/><mml:mn>48</mml:mn></mml:mmultiscripts></mml:math>in the quasielastic peak region

2019-12-30

C. Barbieri , Noemi Rocco , V. Somà

Neutron and proton spectral functions of $^{40}\mathrm{Ar}, ^{40}\mathrm{Ca}$, and $^{48}\mathrm{Ti}$ isotopes are computed using the ab initio self-consistent Green's function approach. The resulting radii and charge distributions are in good … Neutron and proton spectral functions of $^{40}\mathrm{Ar}, ^{40}\mathrm{Ca}$, and $^{48}\mathrm{Ti}$ isotopes are computed using the ab initio self-consistent Green's function approach. The resulting radii and charge distributions are in good agreement with available experimental data. The spectral functions of Ar and Ti are then utilized to calculate inclusive ($e,{e}^{\ensuremath{'}}$) cross sections within a factorization scheme and are found to correctly reproduce the recent Jefferson Lab measurements. Based on these successful agreements, the weak charged and neutral current double-differential cross sections for neutrino-$^{40}\mathrm{Ar}$ scattering are predicted in the quasielastic region. Results obtained by replacing the (experimentally inaccessible) neutron spectral distribution of $^{40}\mathrm{Ar}$ with the (experimentally accessible) proton distribution of $^{48}\mathrm{Ti}$ are compared and the accuracy of this approximation is assessed.

View PDF Chat

SPECTROSCOPIC FACTORS IN 16O AND NUCLEON ASYMMETRY

2009-04-30

C. Barbieri , W. H. Dickhoff

The self-consistent Green's functions method is employed to study the spectroscopic factors of quasiparticle states around 16O, 28O, 40Ca and 60Ca. The Faddeev random phase approximation (FRPA) is used to … The self-consistent Green's functions method is employed to study the spectroscopic factors of quasiparticle states around 16O, 28O, 40Ca and 60Ca. The Faddeev random phase approximation (FRPA) is used to account for the coupling of particles with collective excitation modes. Results for 16O are reviewed first. The same approach is applied to isotopes with large proton-neutron asymmetry to estimate its effect on spectroscopic factors. The results, based on the chiral N3LO force, exhibit an asymmetry dependence similar to that observed in heavy-ion knockout experiments but weaker in magnitude.

View PDF Chat

Extension of the random phase approximation including the self-consistent coupling to two-phonon contributions

2003-07-29

C. Barbieri , W. H. Dickhoff

A microscopic formalism is developed that includes the coupling to two particle-hole phonons in the particle-hole propagator by extending the dressed random phase approximation (DRPA) equation for a finite system. … A microscopic formalism is developed that includes the coupling to two particle-hole phonons in the particle-hole propagator by extending the dressed random phase approximation (DRPA) equation for a finite system. The resulting formalism is applied to study the low-lying excitation spectrum of 16O. It is observed that the coupling to two-phonon states at low energy generates excited states with quantum numbers that cannot be obtained in the DRPA approach. Nevertheless, the two-phonon states mix weakly with particle-hole configurations and participate only partially in the formation of the lowest-lying positive-parity excited states. The stability of the present calculation is tested vs. the truncation of model space. It is demonstrated that when single-particle strength fragmentation is properly considered, the present formalism exhibits convergence with respect to the chosen model space within the confines of the chosen approximation scheme.

View PDF Chat

Algebraic diagrammatic construction formalism with three-body interactions

2018-05-08

Francesco Raimondi , C. Barbieri

Background: Self-consistent Green's function theory has recently been extended to the basic formalism needed to account for three-body interactions [Carbone, Cipollone, Barbieri, Rios, and Polls, Phys. Rev. C 88, 054326 … Background: Self-consistent Green's function theory has recently been extended to the basic formalism needed to account for three-body interactions [Carbone, Cipollone, Barbieri, Rios, and Polls, Phys. Rev. C 88, 054326 (2013)]. The contribution of three-nucleon forces has so far been included in ab initio calculations on nuclear matter and finite nuclei only as averaged two-nucleon forces.Purpose: We derive the working equations for all possible two- and three-nucleon terms that enter the expansion of the self-energy up to the third order, thus including the interaction-irreducible (i.e., not averaged) diagrams with three-nucleon forces that have been previously neglected.Methods: We employ the algebraic diagrammatic construction up to the third order as an organization scheme for generating a nonperturbative self-energy, in which ring (particle-hole) and ladder (particle-particle) diagrams are resummed to all orders.Results: We derive expressions of the static and dynamic self-energy up to the third order, by taking into account the set of diagrams required when either the skeleton or nonskeleton expansions of the single-particle propagator are assumed. A hierarchy of importance among different diagrams is revealed, and a particular emphasis is given to a third-order diagram [see Fig. 2(c)] that is expected to play a significant role among those featuring an interaction-irreducible three-nucleon force.Conclusion: A consistent formalism to resum at infinite order correlations induced by three-nucleon forces in the self-consistent Green's function theory is now available and ready to be implemented in the many-body solvers.

View PDF Chat

Effects of nuclear correlations on the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">O</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>16</mml:mn></mml:mrow></mml:mmultiscripts><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>e</mml:mi><mml:mo>,</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mi>p</mml:mi><mml:mi>N</mml:mi></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math…

2004-07-14

C. Barbieri , C. Giusti , F. D. Pacati +1 more

Calculations of the $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}p\phantom{\rule{0.3em}{0ex}}N)$ cross sections to the ground state and first excited levels of the $^{14}\mathrm{C}$ and $^{14}\mathrm{N}$ nuclei are presented. The effects of nuclear fragmentation have been obtained … Calculations of the $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}p\phantom{\rule{0.3em}{0ex}}N)$ cross sections to the ground state and first excited levels of the $^{14}\mathrm{C}$ and $^{14}\mathrm{N}$ nuclei are presented. The effects of nuclear fragmentation have been obtained in a self-consistent approach and are accounted for in the determination of the two-nucleon removal amplitudes. The Hilbert space is partitioned in order to compute the contribution of both long- and short-range effects in a separate way. Both the two-proton and the proton-neutron emission cross sections have been computed within the same model for the nuclear structure as well as the same treatment of the reaction mechanism, with the aim of better comparing the differences between the two physical processes. The $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}\phantom{\rule{0.3em}{0ex}}pp)$ reaction is found to be sensitive to short-range correlations, in agreement with previous results. The $^{16}\mathrm{O}(e,{e}^{\ensuremath{'}}\phantom{\rule{0.3em}{0ex}}pn)$ cross section to ${1}^{+}$ final states is dominated by the $\ensuremath{\Delta}$ current and tensor correlations. For both reactions, the interplay between collective (long-range) effects and short-range and tensor correlations plays an important role. This suggests that the selectivity of $(e,{e}^{\ensuremath{'}}pN)$ reactions to the final state can be used to probe correlations also beyond short-range effects.

View PDF Chat

Inclusive electron-nucleus cross section within the self-consistent Green's function approach

2018-08-08

Noemi Rocco , C. Barbieri

We present results for charge form factors, the point-proton, charge, and single-nucleon momentum distributions of $^{4}\mathrm{He}$ and $^{16}\mathrm{O}$ obtained within the self-consistent Green's function approach. The removal of the center-of-mass … We present results for charge form factors, the point-proton, charge, and single-nucleon momentum distributions of $^{4}\mathrm{He}$ and $^{16}\mathrm{O}$ obtained within the self-consistent Green's function approach. The removal of the center-of-mass contribution for both nuclei has been performed by using a metropolis Monte Carlo algorithm in which the center-of-mass coordinate can be exactly subtracted from the optimal reference state wave function generated during the self-consistent Green's function calculations. The spectral functions of the same two nuclei have been used to compute inclusive electron-nucleus cross sections. The formalism adopted is based on the factorization of the spectral function and the nuclear transition matrix elements. This allows us to provide an accurate description of nuclear dynamics and to account for relativistic effects in the interaction vertex. When final-state interactions for the struck particle are accounted for, we find nice agreement between the data and the theory for the inclusive electron-$^{16}\mathrm{O}$ cross section. The results lay the foundations for future applications of the self-consistent Green's function method, in both closed and open shell nuclei, to neutrino data analysis.

View PDF Chat

Nuclear electromagnetic dipole response with the self-consistent Green's function formalism

2019-05-24

Francesco Raimondi , C. Barbieri

Microscopic calculations of the electromagnetic response of medium-mass nuclei are now feasible thanks to the availability of realistic nuclear interactions with accurate saturation and spectroscopic properties, and the development of … Microscopic calculations of the electromagnetic response of medium-mass nuclei are now feasible thanks to the availability of realistic nuclear interactions with accurate saturation and spectroscopic properties, and the development of large-scale computing methods for many-body physics. The purpose is to compute isovector dipole electromagnetic (E1) response and related quantities, i.e. integrated dipole cross section and polarizability, and compare with data from photoabsorption and Coulomb excitation experiments. The single-particle propagator is obtained by solving the Dyson equation, where the self-energy includes correlations non-perturbatively through the Algebraic Diagrammatic Construction (ADC) method. The particle-hole ($ph$) polarization propagator is treated in the Dressed Random Phase Approximation (DRPA), based on an effective correlated propagator that includes some $2p2h$ effects but keeps the same computation scaling as the standard Hartree-Fock propagator. The E1 responses for $^{14,16,22,24}$O, $^{36,40,48,52,54,70}$Ca and $^{68}$Ni have been computed: the presence of a soft dipole mode of excitation for neutron-rich nuclei is found, and there is a fair reproduction of the low-energy part of the experimental excitation spectrum. This is reflected in a good agreement with the empirical dipole polarizability values. For a realistic interaction with an accurate reproduction of masses and radii up to medium-mass nuclei, the Self-Consistent Green's Function method provides a good description of the E1 response, especially in the part of the excitation spectrum below the Giant Dipole Resonance. The dipole polarizability is largely independent from the strategy of mapping the dressed propagator to a simplified one that is computationally manageable

View PDF Chat

Single particle spectra based on modern effective interactions

2006-11-08

C. Barbieri

The self-consistent Green's function method is applied to 16O using a G-matrix and VUCOM as effective interactions, both derived from the Argonne v18 potential. The present calculations are performed in … The self-consistent Green's function method is applied to 16O using a G-matrix and VUCOM as effective interactions, both derived from the Argonne v18 potential. The present calculations are performed in a larger model space than previously possible. The experimental single particle spectra obtained with the G-matrix are essentially independent of the oscillator length of the basis. The results shows that VUCOM better reproduces spin–orbit splittings but tends to overestimate the gap at the Fermi energy.

View PDF Chat

Effects of rescattering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>e</mml:mi><mml:mo>,</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mi>p</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>reactions within a semiclassical model

2004-11-24

C. Barbieri , L. Lapikás

The contribution of rescattering to final state interactions in $(e,{e}^{\ensuremath{'}}p)$ cross sections is studied for medium and high missing energies using a semiclassical model. This approach considers two-step processes that … The contribution of rescattering to final state interactions in $(e,{e}^{\ensuremath{'}}p)$ cross sections is studied for medium and high missing energies using a semiclassical model. This approach considers two-step processes that lead to the emission of both nucleons. The effects of nuclear transparency are accounted for in a Glauber-inspired approach and the dispersion effects of the medium at low energies are included. It is found that rescattering is strongly reduced in parallel kinematics. At high missing energies and momenta, the distortion of the short-range correlated tail of the spectral function is dominated by a rearrangement of that strength itself. In perpendicular kinematics, a further enhancement of the experimental yield is due to strength that is originally in the mean field region. This contribution becomes negligible at large missing momenta.

View PDF Chat

Faddeev random-phase approximation for molecules

2011-04-27

Matthias Degroote , Dimitri Van Neck , C. Barbieri

The Faddeev Random Phase Approximation is a Green's function technique that makes use of Faddeev-equations to couple the motion of a single electron to the two-particle--one-hole and two-hole--one-particle excitations. This … The Faddeev Random Phase Approximation is a Green's function technique that makes use of Faddeev-equations to couple the motion of a single electron to the two-particle--one-hole and two-hole--one-particle excitations. This method goes beyond the frequently used third-order Algebraic Diagrammatic Construction method: all diagrams involving the exchange of phonons in the particle-hole and particle-particle channel are retained, but the phonons are described at the level of the Random Phase Approximation. This paper presents the first results for diatomic molecules at equilibrium geometry. The behavior of the method in the dissociation limit is also investigated.

View PDF Chat

Doubly magic nuclei from lattice QCD forces at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>M</mml:mi><mml:mi>PS</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>469</mml:mn><mml:mspace width="0.16em" /><mml:mi>MeV</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math>

2018-02-20

Chris McIlroy , C. Barbieri , Takashi Inoue +2 more

We perform ab initio self-consistent Green's function calculations of the closed shell nuclei $^{\rm 4}$He, $^{\rm 16}$O and $^{\rm 40}$Ca, based on two-nucleon potentials derived from Lattice QCD simulations, in … We perform ab initio self-consistent Green's function calculations of the closed shell nuclei $^{\rm 4}$He, $^{\rm 16}$O and $^{\rm 40}$Ca, based on two-nucleon potentials derived from Lattice QCD simulations, in the flavor SU(3) limit and at the pseudo-scalar meson mass of 469~MeV/c$^{\rm 2}$. The nucleon-nucleon interaction is obtained using the HAL QCD method and its short-distance repulsion is treated by means of ladder resummations outside the model space. Our results show that this approach diagonalises ultraviolet degrees of freedom correctly. Therefore, ground state energies can be obtained from infrared extrapolations even for the relatively hard potentials of HAL QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total binding energies are sensibly improved by the full account of many-body correlations. The results suggest an interesting possible behaviour in which nuclei are unbound at very large pion masses and islands of stability appear at first around the traditional doubly-magic numbers when the pion mass is lowered toward its physical value. The calculated one-nucleon spectral distributions are qualitatively close to those of real nuclei even for the pseudo-scalar meson mass considered here.

View PDF Chat

Quenching of single-particle strength from direct reactions with stable and rare-isotope beams

2021-01-08

T. Aumann , C. Barbieri , D. Bazin +7 more

In this review article we discuss the present status of direct nuclear reactions and the nuclear structure aspects one can study with them. We discuss the spectroscopic information we can … In this review article we discuss the present status of direct nuclear reactions and the nuclear structure aspects one can study with them. We discuss the spectroscopic information we can assess in experiments involving transfer reactions, heavy-ion-induced knockout reactions and quasifree scattering with (p,2p), (p,pn), and (e,e'p) reactions. In particular, we focus on the proton-to-neutron asymmetry of the quenching of the spectroscopic strength.

View PDF Chat

First measurements of the 16O(e, e'pn)14N reaction

2006-09-01

D. G. Middleton , J. R. M. Annand , C. Barbieri +7 more

View PDF Chat

Nuclear energy density functionals grounded in ab initio calculations

2021-08-09

F. Marino , C. Barbieri , Arianna Carbone +5 more

We discuss the construction of a nuclear energy density functional (EDF) from ab initio computations and advocate the need for a methodical approach that is free from ad hoc assumptions. … We discuss the construction of a nuclear energy density functional (EDF) from ab initio computations and advocate the need for a methodical approach that is free from ad hoc assumptions. The equations of state (EoSs) of symmetric nuclear and pure neutron matter are computed using the chiral ${\mathrm{NNLO}}_{\mathrm{sat}}$ and the phenomenological ${\mathrm{AV4}}^{\ensuremath{'}}+{\mathrm{UIX}}_{c}$ Hamiltonians as inputs to self-consistent Green's function (SCGF) and auxiliary field diffusion Monte Carlo (AFDMC) methods. We propose a convenient parametrization of the EoS as a function of the Fermi momentum and fit it on the SCGF and AFDMC calculations. We apply the ab initio based EDF to carry out an analysis of the binding energies and charge radii of different nuclei in the local density approximation. The ${\mathrm{NNLO}}_{\mathrm{sat}}$-based EDF produces encouraging results, whereas the ${\mathrm{AV4}}^{\ensuremath{'}}+{\mathrm{UIX}}_{c}$-based one is farther from experiment. Possible explanations of these different behaviors are suggested, and the importance of gradient and spin-orbit terms is analyzed. Our paper paves the way for a practical and systematic way to merge ab initio nuclear theory and density functional theory, while shedding light on some critical aspects of this procedure.

View PDF Chat

Effect of kinematics on final state interactions in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:mi>e</mml:mi><mml:mtext>,</mml:mtext><mml:msup><mml:mi>e</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mi>p</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math> reactions

2005-01-05

C. Barbieri , D. Rohe , I. Sick +1 more

Recent data from experiment E97-006 at TJNAF using the 12C(e,e'p) reaction at very large missing energies and momenta are compared to a calculation of two-step rescattering. A comparison between parallel … Recent data from experiment E97-006 at TJNAF using the 12C(e,e'p) reaction at very large missing energies and momenta are compared to a calculation of two-step rescattering. A comparison between parallel and perpendicular kinematics suggests that the effects of final state interactions can be strongly reduced in the former case.

View PDF Chat

Gorkov algebraic diagrammatic construction formalism at third order

2022-04-28

C. Barbieri , T. Duguet , V. Somà

Background. The Gorkov approach to self-consistent Green's function theory has been formulated in [V. Som\`a, T. Duguet, C. Barbieri, Phys. Rev. C 84, 064317 (2011)]. Over the past decade, it … Background. The Gorkov approach to self-consistent Green's function theory has been formulated in [V. Som\`a, T. Duguet, C. Barbieri, Phys. Rev. C 84, 064317 (2011)]. Over the past decade, it has become a method of reference for first-principle computations of semi-magic nuclear isotopes. The currently available implementation is limited to a second-order self-energy and neglects particle-number non-conserving terms arising from contracting three-particle forces with anomalous propagators. For nuclear physics applications, this is sufficient to address first-order energy differences, ground-state radii and moments on an accurate enough basis. However, addressing absolute binding energies, fine spectroscopic details of $N\pm1$ particle systems or delicate quantities such as second-order energy differences associated to pairing gaps, requires to go to higher truncation orders. Purpose. The formalism is extended to third order in the algebraic diagrammatic construction (ADC) expansion with two-body Hamiltonians. Methods. The expansion of Gorkov propagators in Feynman diagrams is combined with the algebraic diagrammatic construction up to the third order as an organization scheme to generate the Gorkov self-energy. Results. Algebraic expressions for the static and dynamic contributions to the self-energy, along with equations for the matrix elements of the Gorkov eigenvalue problem, are derived. It is first done for a general basis before specifying the set of equations to the case of spherical systems displaying rotational symmetry. Workable approximations to the full self-consistency problem are also elaborated on. The formalism at third order it thus complete for a general two-body Hamiltonian. Conclusion. Working equations for the full Gorkov-ADC(3) are now available for numerical implementation.

View PDF Chat

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

2017-01-01

A. Idini , C. Barbieri , P. Navrátil

We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials.The potential is derived using self consistent Green's function … We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials.The potential is derived using self consistent Green's function theory (SCGF) with the saturating chiral interaction NNLO sat .Our calculations are compared to available scattering data and show that it is possible to reproduce low energy scattering observables in medium mass nuclei from first principles.

View PDF Chat

Neutron spectroscopic factors of 55 Ni hole-states from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mo stretchy="false">(</mml:mo><mml:mi mathvariant="normal">p</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">d</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>transfer reactions

2014-07-07

A. Sanetullaev , M. B. Tsang , W. G. Lynch +7 more

Spectroscopic information has been extracted on the hole-states of $^{55}$Ni, the least known of the quartet of nuclei ($^{55}$Ni, $^{57}$Ni, $^{55}$Co and $^{57}$Co), one neutron away from $^{56}$Ni, the N=Z=28 … Spectroscopic information has been extracted on the hole-states of $^{55}$Ni, the least known of the quartet of nuclei ($^{55}$Ni, $^{57}$Ni, $^{55}$Co and $^{57}$Co), one neutron away from $^{56}$Ni, the N=Z=28 double magic nucleus. Using the $^{1}$H($^{56}$Ni,d)$^{55}$Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f$_{7/2}$, p$_{3/2}$ and the s$_{1/2}$ hole-states of $^{55}$Ni. This new data provides a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s$_{1/2}$ hole-state below Fermi energy.

View PDF Chat

Examining the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>28</mml:mn></mml:mrow></mml:math> shell closure through high-precision mass measurements of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ar</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>46</mml:mn><mml:mtext>–</mml:mtext><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>

2020-07-01

M. Mougeot , D. Atanasov , C. Barbieri +7 more

The strength of the $N=28$ magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of $^{46\text{--}48}\mathrm{Ar}$, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass … The strength of the $N=28$ magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of $^{46\text{--}48}\mathrm{Ar}$, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the $N=28$ shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the SDPF-U phenomenological shell model interaction. Our results are also compared with ab initio calculations using the valence space in-medium similarity renormalization group and the self-consistent Green's function approaches. Both calculations provide a very good account of mass systematics at and around $Z=18$ and, generally, a consistent description of the physics in this region. This combined analysis indicates that $^{46}\mathrm{Ar}$ is the transition between the closed-shell $^{48}\mathrm{Ca}$ and collective $^{44}\mathrm{S}$.

View PDF Chat

Examination of the sensitivity of quasifree reactions to details of the bound-state overlap functions

2021-12-14

C. A. Bertulani , A. Idini , C. Barbieri

It is often stated that heavy-ion nucleon knockout reactions are mostly sensitive to the tails of the bound-state wavefunctions. In contrast, (p,2p) and (p,pn) reactions are known to access information … It is often stated that heavy-ion nucleon knockout reactions are mostly sensitive to the tails of the bound-state wavefunctions. In contrast, (p,2p) and (p,pn) reactions are known to access information on the full overlap functions within the nucleus. We analyze the oxygen isotopic chain and explore the differences between single-particle wave functions generated with potential models, used in the experimental analysis of knockout reactions, and ab initio computations from self-consistent Green's function theory. Contrary to the common belief, we find that not only the tail of the overlap functions, but also their internal part are assessed in both reaction mechanisms, which are crucial to yield accurately determined spectroscopic information.

View PDF Chat

Many-body Propagator Theory with Three-Body Interactions: a Path to Exotic Open Shell Isotopes

2014-08-14

C. Barbieri

Ab-initio predictions of nuclei with masses up to A~100 or more is becoming possible thanks to novel advances in computations and in the formalism of many-body physics. Some of the … Ab-initio predictions of nuclei with masses up to A~100 or more is becoming possible thanks to novel advances in computations and in the formalism of many-body physics. Some of the most fundamental issues include how to deal with many-nucleon interactions, how to calculate degenerate--open shell--systems, and pursuing ab-initio approaches to reaction theory. Self-consistent Green's function (SCGF) theory is a natural approach to address these challenges. Its formalism has recently been extended to three- and many-body interactions and reformulated within the Gorkov framework to reach semi-magic open shell isotopes. These exciting developments, together with the predictive power of chiral nuclear Hamiltonians, are opening the path to understanding large portions of the nuclear chart, especially within the $sd$ and $pf$ shells. The present talk reviews the most recent advances in ab-initio nuclear structure and many-body theory that have been possible through the SCGF approach.

View PDF Chat

Diagrammatic Monte Carlo for Finite Systems at Zero Temperature

2025-05-09

Stefano Brolli , C. Barbieri , E. Vigezzi

High-order virtual excitations play an important role in microscopic models of nuclear reactions at intermediate energies. However, the factorial growth of their complexity has prevented their consistent inclusion in ab … High-order virtual excitations play an important role in microscopic models of nuclear reactions at intermediate energies. However, the factorial growth of their complexity has prevented their consistent inclusion in ab initio many-body calculations. For infinite systems at finite temperature, such drawbacks can be overcome using diagrammatic Monte Carlo techniques to resum entire series of Feynman diagrams. We present a diagrammatic Monte Carlo algorithm that can be applied to self-bound systems with discrete energy levels at zero temperature, and demonstrate its potential for the Richardson model of nuclear pairing. We show that sampling the topological space of diagrams allows the inclusion of high-order excitations that are neglected in state-of-the-art approximations used in nuclear physics and quantum chemistry. We propose that sampling the diagrammatic space can overcome the long-standing gap between our microscopic understanding of structure and reactions in nuclear physics.

View PDF Chat

Diagrammatic Monte Carlo for finite systems at zero temperature

2025-01-05

Stefano Brolli , C. Barbieri , E. Vigezzi

High-order virtual excitations play an important role in microscopic models of nuclear reactions at intermediate energies. However, the factorial growth of their complexity has prevented their consistent inclusion in ab … High-order virtual excitations play an important role in microscopic models of nuclear reactions at intermediate energies. However, the factorial growth of their complexity has prevented their consistent inclusion in ab initio many-body calculations. For infinite systems at finite temperature, such drawbacks can be overcome using diagrammatic Monte Carlo (DiagMC) techniques to resum entire series of Feynman diagrams. We present a DiagMC algorithm that can be applied to self-bound systems with discrete energy levels at zero temperature, and demonstrate its potential for the Richardson model of nuclear pairing. We show that sampling the topological space of diagrams allows the inclusion of high-order excitations that are neglected in state-of-the-art approximations used in nuclear physics and quantum chemistry. We propose that sampling the diagrammatic space can overcome the long-standing gap between our microscopic understanding of structure and reactions in nuclear physics.

View PDF Chat

Simulation of a Three‐Nucleons System Transition on Quantum Circuits

2024-12-11

Luciano Nigro , C. Barbieri , Enrico Prati

Quantum computers have proven to be effective in simulating many quantum systems. Simulating nuclear processes and state preparation poses significant challenges, even for traditional supercomputers. This study demonstrates the feasibility … Quantum computers have proven to be effective in simulating many quantum systems. Simulating nuclear processes and state preparation poses significant challenges, even for traditional supercomputers. This study demonstrates the feasibility of a complete simulation of a nuclear transition, including the preparation of both ground and first excited states. To tackle the complexity of strong interactions between two and three nucleons, the states are modeled on the tritium nucleus. Both the initial and final states are represented using quantum circuits with variational quantum algorithms and inductive biases. Describing the spin-isospin states requires four qubits, and a parameterized quantum circuit that exploits a total of 16 parameters is initialized. The estimated energy has a relative error of approximately 2% for the ground state and about 10% for the first excited state of the system. The simulation estimates the transition probability between the two states as a function of the dipole polarization angle. This work marks a first step towards leveraging digital quantum computers to simulate nuclear physics.

View PDF Chat

Ab initio Green's functions approach for homogeneous nuclear matter

2024-09-11

Francesco Marino , C. Barbieri , G. Colò +2 more

Homogeneous nuclear matter is investigated using the \textit{ab initio} Self-consistent Green's function (SCGF) approach with nuclear interactions based on chiral effective field theory. The employed method, which combines the state-of-the-art … Homogeneous nuclear matter is investigated using the \textit{ab initio} Self-consistent Green's function (SCGF) approach with nuclear interactions based on chiral effective field theory. The employed method, which combines the state-of-the-art algebraic diagrammatic construction approximation at third order with Gorkov correlations, is capable of computing both the equation of state (EOS) and single-particle properties of nuclear matter. The EOS calculated with our approach and coupled-cluster theory are shown to agree very well. The one-nucleon spectral functions and the momentum distributions are discussed to gain insights into the dynamics of the interacting nuclear matter.

View PDF Chat

Nambu-covariant many-body theory II: Self-consistent approximations

2024-07-11

M. Drissi , Arnau Rios , C. Barbieri

View PDF Chat

Nambu-covariant many-body theory I: Perturbative approximations

2024-07-08

M. Drissi , Arnau Rios , C. Barbieri

View PDF Chat

Expansion of one-, two- and three-body matrix elements on a generic spherical basis for nuclear ab initio calculations

2024-05-15

A. Scalesi , C. Barbieri , E. Vigezzi

Ab initio studies of atomic nuclei are based on Hamiltonians including one-, two- and three-body operators with very complicated structures. Traditionally, matrix elements of such operators are expanded on a … Ab initio studies of atomic nuclei are based on Hamiltonians including one-, two- and three-body operators with very complicated structures. Traditionally, matrix elements of such operators are expanded on a Harmonic Oscillator single-particle basis, which allows for a simple separation of the center-of-mass motion from the intrinsic one. A few recent investigations have showed that the use of different single-particle bases can bring significant advantages to numerical nuclear structure computations. In this work, the complete analytical expression of the Hamiltonian matrix elements expanded on a generic spherical basis is presented for the first time. This will allow systematic studies aimed at the determination of optimal nuclear bases.

View PDF Chat

Microscopic optical potentials for medium-mass isotopes derived at the first order of Watson multiple-scattering theory

2024-03-15

Matteo Vorabbi , C. Barbieri , V. Somà +2 more

We perform a first-principles calculation of optical potentials for nucleon elastic scattering off medium-mass isotopes. Fully based on a saturating chiral Hamiltonian, the optical potentials are derived by folding nuclear … We perform a first-principles calculation of optical potentials for nucleon elastic scattering off medium-mass isotopes. Fully based on a saturating chiral Hamiltonian, the optical potentials are derived by folding nuclear density distributions computed with self-consistent Green's function theory with a nucleon-nucleon <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>t</a:mi></a:math> matrix computed with a consistent chiral interaction. The dependence on the folding interaction as well as the convergence of the target densities are investigated. Numerical results are presented and discussed for differential cross sections and analyzing powers, with focus on elastic proton scattering off calcium and nickel isotopes. Our optical potentials generally show a remarkable agreement with the available experimental data for laboratory energies in the range 65–200 MeV. We study the evolution of the scattering observables with increasing proton-neutron asymmetry by computing theoretical predictions of the cross section and analyzing power over the calcium and nickel isotopic chains. Published by the American Physical Society 2024

View PDF Chat

Expansion of One-, Two- and Three-Body Matrix Elements on a Generic Spherical Basis for Nuclear Ab Initio Calculations

2024-01-01

A. Scalesi , C. Barbieri , E. Vigezzi

View PDF Chat

Quantum Monte Carlo calculations in configuration space with three-nucleon forces

2023-04-05

P. Arthuis , C. Barbieri , Francesco Pederiva +1 more

Neutron matter, through its connection to neutron stars as well as systems such as cold atom gases, is one of the most interesting yet computationally accessible systems in nuclear physics. … Neutron matter, through its connection to neutron stars as well as systems such as cold atom gases, is one of the most interesting yet computationally accessible systems in nuclear physics. The configuration-interaction Monte Carlo (CIMC) method is a stochastic many-body technique allowing us to tackle strongly coupled systems. In contrast to other quantum Monte Carlo methods employed in nuclear physics, the CIMC method can be formulated directly in momentum space allowing for an efficient use of nonlocal interactions. In this work we extend CIMC method to include three-nucleon interactions through the normal-ordered two-body approximation. We present results for the equation of state of neutron matter in line with other many-body calculations that employ low-resolution chiral interactions, and provide predictions for the momentum distribution and the static structure factor.

View PDF Chat

Optical potentials for the rare-isotope beam era

2023-03-10

C. Hebborn , F. M. Nunes , G. Potel +7 more

View PDF Chat

Microscopic optical potentials for medium-mass isotopes derived at the first order of the Watson multiple scattering theory

2023-01-01

Matteo Vorabbi , C. Barbieri , V. Somà +2 more

We perform a first-principle calculation of optical potentials for nucleon elastic scattering off medium-mass isotopes. Fully based on a saturating chiral Hamiltonian, the optical potentials are derived by folding nuclear … We perform a first-principle calculation of optical potentials for nucleon elastic scattering off medium-mass isotopes. Fully based on a saturating chiral Hamiltonian, the optical potentials are derived by folding nuclear density distributions computed with ab initio self-consistent Green's function theory with a nucleon-nucleon $t$ matrix computed with a consistent chiral interaction. The dependence on the folding interaction as well as the convergence of the target densities are investigated. Numerical results are presented and discussed for differential cross sections and analyzing powers, with focus on elastic proton scattering off Calcium and Nickel isotopes. Our optical potentials generally show a remarkable agreement with the available experimental data for laboratory energies in the range 65-200 MeV. We study the evolution of the scattering observables with increasing proton-neutron asymmetry by computing theoretical predictions of the cross section and analyzing power over the Calcium and Nickel isotopic chains.

Expansion of one-, two- and three-body matrix elements on a generic spherical basis for nuclear ab initio calculations

2023-01-01

A. Scalesi , C. Barbieri , E. Vigezzi

View PDF Chat

Gorkov algebraic diagrammatic construction formalism at third order

2022-04-28

C. Barbieri , T. Duguet , V. Somà

View PDF Chat

A first glimpse at the shell structure beyond 54Ca: Spectroscopy of 55K, 55Ca, and 57Ca

2022-02-11

T. Koiwai , K. Wimmer , P. Doornenbal +7 more

States in the $N=35$ and 37 isotopes $^{55,57}$Ca have been populated by direct proton-induced nucleon removal reactions from $^{56,58}$Sc and $^{56}$Ca beams at the RIBF. In addition, the $(p,2p)$ quasi-free … States in the $N=35$ and 37 isotopes $^{55,57}$Ca have been populated by direct proton-induced nucleon removal reactions from $^{56,58}$Sc and $^{56}$Ca beams at the RIBF. In addition, the $(p,2p)$ quasi-free single-proton removal reaction from $^{56}$Ca was studied. Excited states in $^{55}$K, $^{55}$Ca, and $^{57}$Ca were established for the first time via in-beam $\gamma$-ray spectroscopy. Results for the proton and neutron removal reactions from $^{56}$Ca to states in $^{55}$K and $^{55}$Ca for the level energies, excited state lifetimes, and exclusive cross sections agree well with state-of-the-art theoretical calculations using different approaches. The observation of a short-lived state in $^{57}$Ca suggests a transition in the calcium isotopic chain from single-particle dominated states at $N=35$ to collective excitations at $N=37$.

View PDF Chat

Nuclear Charge Radii of the Nickel Isotopes <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ni</mml:mi></mml:mrow><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>58</mml:mn><mml:mo>−</mml:mo><mml:mn>68</mml:mn><mml:mo>,</mml:mo><mml:mn>70</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>

2022-01-14

S. Malbrunot-Ettenauer , S. Kaufmann , Sonia Bacca +7 more

View PDF Chat

Quantum Monte Carlo in Configuration Space with Three-Nucleon Forces

2022-01-01

P. Arthuis , C. Barbieri , Francesco Pederiva +1 more

Neutron matter, through its connection to neutron stars as well as systems like cold atom gases, is one of the most interesting yet computationally accessible systems in nuclear physics. The … Neutron matter, through its connection to neutron stars as well as systems like cold atom gases, is one of the most interesting yet computationally accessible systems in nuclear physics. The Configuration-Interaction Monte Carlo (CIMC) method is a stochastic many-body technique allowing to tackle strongly coupled systems. In contrast to other Quantum Monte Carlo methods employed in nuclear physics, the CIMC method can be formulated directly in momentum space allowing for an efficient use of non-local interactions. In this work we extend CIMC method to include three-nucleon interactions through the normal-ordered two-body approximation. We present results for the equation of state of neutron matter in line with other many-body calculations that employ low resolution chiral interactions, and provide predictions for the momentum distribution and the static structure factor.

View PDF Chat

Examination of the sensitivity of quasifree reactions to details of the bound-state overlap functions

2021-12-14

C. A. Bertulani , A. Idini , C. Barbieri

View PDF Chat

Sensitivity of quasi-free reactions on details of the bound-state overlap functions.

2021-11-30

C. A. Bertulani , A. Idini , C. Barbieri

Investigation of the ground-state spin inversion in the neutron-rich <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Cl</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>47</mml:mn><mml:mo>,</mml:mo><mml:mn>49</mml:mn></mml:mrow></mml:mmultiscripts></mml:math> isotopes

2021-10-29

B. D. Linh , A. Corsi , A. Gillibert +7 more

A first gamma-ray study of 47,49Cl spectroscopy was performed at the Radioactive Isotope Beam Factory with 50Ar projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS … A first gamma-ray study of 47,49Cl spectroscopy was performed at the Radioactive Isotope Beam Factory with 50Ar projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS device. Prompt de-excitation gamma-rays were measured with the NaI(Tl) array DALI2+. Through the one-proton knockout reaction 50Ar(p,2p), a spin assignment could be determined for the low-lying states of 49Cl from the momentum distribution obtained with the SAMURAI spectrometer. A spin-parity J = 3/2+ is deduced for the ground state of 49Cl, similar to the recently studied N = 32 isotope 51K.

View PDF Chat

The tale of tails: Sensitivity of quasi-free reactions on details of the bound-state overlap functions

2021-08-29

C. A. Bertulani , A. Idini , C. Barbieri

It is often stated that one-nucleon knockout in reactions with heavy ion targets are mostly sensitive to the tails of the bound-state wavefunctions. In contrast, (p,2p) and (p,pn) reactions are … It is often stated that one-nucleon knockout in reactions with heavy ion targets are mostly sensitive to the tails of the bound-state wavefunctions. In contrast, (p,2p) and (p,pn) reactions are known to access information on the full overlap functions within the nucleus. We analyze the oxygen isotopic chain and explore the differences between single-particle wave functions generated with potential models, used in the experimental analysis of knockout reactions, and ab initio computations from self-consistent Green's function theory. Contrary to the common belief, we find that not only the tail of the overlap functions, but also information on their internal part are assessed in both reaction mechanisms, which are crucial to yield accurately determined spectroscopic information. The recent revival of (p,2p) reactions, this time in inverse kinematic experiments, will help improve studies of unstable nuclei if combined with a better experimental analysis with inputs from many-body ab initio theories. We suggest that input from state-of-the-art ab initio computations will be fundamental to quantify model dependencies in the analysis of experiments.

Nuclear energy density functionals grounded in ab initio calculations

2021-08-09

F. Marino , C. Barbieri , Arianna Carbone +5 more

View PDF Chat

Moving away from singly-magic nuclei with Gorkov Green’s function theory

2021-04-01

V. Somà , C. Barbieri , T. Duguet +1 more

View PDF Chat

Editorial: The Future of Nuclear Structure: Challenges and Opportunities in the Microscopic Description of Nuclei

2021-02-05

L. Coraggio , Saori Pastore , C. Barbieri

EDITORIAL article Front. Phys., 05 February 2021 | https://doi.org/10.3389/fphy.2020.626976 EDITORIAL article Front. Phys., 05 February 2021 | https://doi.org/10.3389/fphy.2020.626976

View PDF Chat

Editorial: The Future of Nuclear Structure: Challenges and Opportunities in the Microscopic Description of Nuclei

2021-01-20

L. Coraggio , Saori Pastore , C. Barbieri

The past two decades have witnessed tremendous progress in the microscopic description of atomic nuclei. The Topical Review `The Future of Nuclear Structure' aims at summarizing the current state-of-the-art microscopic … The past two decades have witnessed tremendous progress in the microscopic description of atomic nuclei. The Topical Review `The Future of Nuclear Structure' aims at summarizing the current state-of-the-art microscopic calculations in Nuclear Theory and to give a useful reference for young researches who wish to learn more about this exciting discipline.

Quenching of single-particle strength from direct reactions with stable and rare-isotope beams

2021-01-08

T. Aumann , C. Barbieri , D. Bazin +7 more

View PDF Chat

Editorial: The Future of Nuclear Structure: Challenges and Opportunities in the Microscopic Description of Nuclei

2021-01-01

L. Coraggio , Saori Pastore , C. Barbieri

View PDF Chat

Ab Initio Computation of Charge Densities for Sn and Xe Isotopes

2020-10-28

P. Arthuis , C. Barbieri , Matteo Vorabbi +1 more

View PDF Chat

Examining the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>28</mml:mn></mml:mrow></mml:math> shell closure through high-precision mass measurements of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ar</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>46</mml:mn><mml:mtext>–</mml:mtext><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>

2020-07-01

M. Mougeot , D. Atanasov , C. Barbieri +7 more

View PDF Chat

Model nuclear energy density functionals derived from ab initio calculations

2020-04-27

G. Salvioni , J. Dobaczewski , C. Barbieri +3 more

We present the first application of a new approach, proposed in [Journal of Physics G: Nuclear and Particle Physics, 43, 04LT01 (2016)] to derive coupling constants of the Skyrme energy … We present the first application of a new approach, proposed in [Journal of Physics G: Nuclear and Particle Physics, 43, 04LT01 (2016)] to derive coupling constants of the Skyrme energy density functional (EDF) from ab initio Hamiltonian. By perturbing the ab initio Hamiltonian with several functional generators defining the Skyrme EDF, we create a set of metadata that is then used to constrain the coupling constants of the functional. We use statistical analysis to obtain such an ab initio-equivalent Skyrme EDF. We find that the resulting functional describes properties of atomic nuclei and infinite nuclear matter quite poorly. This may point out to the necessity of building up the ab initio-equivalent functionals from more sophisticated generators. However, we also indicate that the current precision of the ab initio calculations may be insufficient for deriving meaningful nuclear EDFs.

View PDF Chat

Novel chiral Hamiltonian and observables in light and medium-mass nuclei

2020-01-22

V. Somà , P. Navrátil , Francesco Raimondi +2 more

View PDF Chat

Lepton scattering from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ar</mml:mi><mml:mprescripts/><mml:none/><mml:mn>40</mml:mn></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Ti</mml:mi><mml:mprescripts/><mml:none/><mml:mn>48</mml:mn></mml:mmultiscripts></mml:math>in the quasielastic peak region

2019-12-30

C. Barbieri , Noemi Rocco , V. Somà

View PDF Chat

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

2019-08-26

A. Idini , C. Barbieri , P. Navrátil

View PDF Chat

Core-polarization effects and effective charges in O and Ni isotopes from chiral interactions

2019-08-12

Francesco Raimondi , C. Barbieri

Background: Many nuclear structure calculations, even for full configuration interaction approaches, are performed with input Hamiltonians represented in a truncated model space. These often require consistent transformations of the operators … Background: Many nuclear structure calculations, even for full configuration interaction approaches, are performed with input Hamiltonians represented in a truncated model space. These often require consistent transformations of the operators to account for the missing physics beyond the active space, so that several recent efforts have been devoted to find compatible derivations of the effective operators. The effective charges employed in the shell-model calculations, and fitted to reproduce experimental data, can be seen as the phenomenological counterpart of such renormalization for electromagnetic operators.Purpose: A coherent mapping of ab initio approaches into shell-model valence spaces requires a consistent derivation of effective electromagnetic operators. Here, we make a first step to lay the bases for their microscopic derivation in the context of the self-consistent Green's function approach.Methods: We compute electric quadrupole ($E2$) effective charges from microscopic theory by coupling the single-nucleon propagators to core-polarization phonons, derived consistently from a realistic nuclear interaction. Nuclear correlations are included nonperturbatively according to the third-order algebraic diagrammatic construction and the Faddeev random-phase approximation. The polarization effects are included by evaluating the Feynman diagrams that couple the intermediate multinucleon configurations to the single-particle transitions induced by the electromagnetic operator.Results: The effective charges for E2 static moments and transitions are computed for selected isotopes in the oxygen ($^{14}\mathrm{O}, ^{16}\mathrm{O}, ^{22}\mathrm{O}$, and $^{24}\mathrm{O}$) and nickel ($^{48}\mathrm{Ni}, ^{56}\mathrm{Ni}, ^{68}\mathrm{Ni}$, and $^{78}\mathrm{Ni}$) chains. The values found are orbital dependent, especially for the neutron effective charges, which also show a characteristic decreasing trend along each isotopic chain. In general, the values are compatible with the phenomenological ones commonly used for shell-model studies in the $0p\phantom{\rule{0.16em}{0ex}}1s\phantom{\rule{0.16em}{0ex}}0d$ and $1p\phantom{\rule{0.16em}{0ex}}0f\phantom{\rule{0.16em}{0ex}}0{g}_{\frac{9}{2}}$ valence spaces.Conclusion: The phenomenological shell-model effective charges can be explained through ab initio approaches, where the sole experimental input comes from the fitting of the realistic nuclear interaction. Effective electromagnetic operators can be derived, which are tailored for different valence spaces and for specific numbers of active nucleons.

View PDF Chat

Nuclear electromagnetic dipole response with the self-consistent Green's function formalism

2019-05-24

Francesco Raimondi , C. Barbieri

View PDF Chat

Neutrino-nucleus cross section within the extended factorization scheme

2019-02-11

Noemi Rocco , C. Barbieri , Omar Benhar +2 more

View PDF Chat

Inclusive electron-nucleus cross section within the self-consistent Green's function approach

2018-08-08

Noemi Rocco , C. Barbieri

View PDF Chat

Algebraic diagrammatic construction formalism with three-body interactions

2018-05-08

Francesco Raimondi , C. Barbieri

View PDF Chat

Doubly magic nuclei from lattice QCD forces at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>M</mml:mi><mml:mi>PS</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>469</mml:mn><mml:mspace width="0.16em" /><mml:mi>MeV</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>c</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math>

2018-02-20

Chris McIlroy , C. Barbieri , Takashi Inoue +2 more

View PDF Chat

Dawning of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:math> Shell Closure Seen through Precision Mass Measurements of Neutron-Rich Titanium Isotopes

2018-02-09

E. Leistenschneider , M. P. Reiter , Samuel Ayet San Andrés +7 more

View PDF Chat

Recent Applications of Self-Consistent Green’s Function Theory to Nuclei

2018-02-01

C. Barbieri , Francesco Raimondi , Christopher McIlroy

We discuss recent ab initio calculations based on self-consistent Green's function theory. It is found that a simple extension of the formalism to account for two-nucleon scattering outside the model … We discuss recent ab initio calculations based on self-consistent Green's function theory. It is found that a simple extension of the formalism to account for two-nucleon scattering outside the model space allows to calculate non-soft interactions. With this, it is possible to make predictions for Lattice QCD potentials, obtained so far at pion masses of mπ = 0.47 GeV/c2. More traditional calculations that use saturating chiral EFT forces yield a good description of nuclear responses and nucleon knockout spectroscopy.

View PDF Chat

Ab initio calculation of the potential bubble nucleus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi mathvariant="normal">Si</mml:mi><mml:mprescripts /><mml:none /><mml:mn>34</mml:mn></mml:mmultiscripts></mml:math>

2017-03-23

T. Duguet , V. Somà , S. Lecluse +2 more

View PDF Chat

Self-Consistent Green’s Function Approaches

2017-01-01

C. Barbieri , Arianna Carbone

View PDF Chat

Irreducible 3-body forces contributions to the self-energy

2017-01-01

Francesco Raimondi , C. Barbieri

The inclusion of the three-nucleon forces (3NFs) in \textit{ab initio} many-body approaches is a formidable task, due to the computational load implied by the treatment of their matrix elements. For … The inclusion of the three-nucleon forces (3NFs) in \textit{ab initio} many-body approaches is a formidable task, due to the computational load implied by the treatment of their matrix elements. For this reason, practical applications have mostly been limited to contributions where 3NFs enter as effective two-nucleon interactions. In this contribution, we derive the algebraic diagrammatic construction (ADC) working equations for a specific Feynman diagram of the self-energy that contains a fully irreducible three-nucleon force. This diagram is expected to be the most important among those previously neglected, because it connects dominant excited intermediate state configurations.

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

2017-01-01

A. Idini , C. Barbieri , P. Navrátil

View PDF Chat

Radii and Binding Energies in Oxygen Isotopes: A Challenge for Nuclear Forces

2016-07-27

V. Lapoux , V. Somà , C. Barbieri +3 more

View PDF Chat

Nuclear astrophysics with radioactive ions at FAIR

2016-01-05

R. Reifarth , S. Altstadt , K. Göbel +7 more

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they … The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process, β-decay chains. These nuclei are attributed to the p and rp process.

View PDF Chat

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

2015-07-10

Andrea Cipollone , C. Barbieri , P. Navrátil

View PDF Chat

Probing the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:math>Shell Closure below the Magic Proton Number<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi><mml:mo>=</mml:mo><mml:mn>20</mml:mn></mml:mrow></mml:math>: Mass Measurements of the Exotic Isotopes<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts…

2015-05-20

M. Rosenbusch , P. Ascher , D. Atanasov +7 more

View PDF Chat

Hierarchical spin glasses in a magnetic field: A renormalization-group study

2015-01-26

Michele Castellana , C. Barbieri

By using renormalization-group (RG) methods, we study a non-mean-field model of a spin glass built on a hierarchical lattice, the hierarchical Edwards-Anderson model in a magnetic field. We investigate the … By using renormalization-group (RG) methods, we study a non-mean-field model of a spin glass built on a hierarchical lattice, the hierarchical Edwards-Anderson model in a magnetic field. We investigate the spin-glass transition in a field by studying the existence of a stable critical RG fixed point (FP) with perturbation theory. In the parameter region where the model has a mean-field behavior---corresponding to $d\ensuremath{\ge}4$ for a $d$-dimensional Ising model---we find a stable FP that corresponds to a spin-glass transition in a field. In the non-mean-field parameter region the FP above is unstable, and we determine exactly all other FPs: to our knowledge, this is the first time that all perturbative FPs for the full set of RG equations of a spin glass in a field have been characterized in the non-mean-field region. We find that all potentially stable FPs in the non-mean-field region have a nonzero imaginary part: this constitutes, to the best of our knowledge, the first demonstration for a spin glass in a field that there is no perturbative FP corresponding to a spin-glass transition in the non-mean-field region. Finally, we discuss the possible interpretations of this result, such as the absence of a phase transition in a field or the existence of a transition associated with a nonperturbative FP.

View PDF Chat

Coauthor	Papers Together
V. Somà	20
P. Navrátil	15
T. Duguet	15
W. H. Dickhoff	14
A. Idini	7
Andrea Cipollone	7
C. Giusti	6
Francesco Raimondi	6
J. D. Holt	6
E. Vigezzi	6
Dimitri Van Neck	5
C. A. Bertulani	5
L. Lapikás	5
T. Aumann	4
Y. Utsuno	4
T. Nakamura	4
Arnau Rios	4
Matteo Vorabbi	4
V. Lapoux	3
A. Scalesi	3
L. Stuhl	3
Y. Togano	3
A. Schwenk	3
K. Blaum	3
Francesco Pederiva	3
V. Panin	3
D. Sohler	3
Paolo Finelli	3
K. Wimmer	3
B.K. Jennings	3
I. Gašparić	3
M. Hjorth‐Jensen	3
P.-A. Söderström	3
Kazuyuki Ogata	3
Noemi Rocco	3
Matthias Degroote	3
P. Arthuis	3
T. Motobayashi	3
L. Coraggio	3
S. R. Stroberg	3
Т. Уесака	3
Κ. Zuber	3
Saori Pastore	3
Arianna Carbone	3
F. D. Pacati	3
A. Obertelli	3
L. X. Chung	2
D. Rohe	2
A. Corsi	2
T. Koiwai	2

Self-consistent Green's function method for nuclei and nuclear matter

2004-04-01

W. H. Dickhoff , C. Barbieri

View PDF Chat

Ab initioself-consistent Gorkov-Green's function calculations of semimagic nuclei: Formalism at second order with a two-nucleon interaction

2011-12-19

V. Somà , T. Duguet , C. Barbieri

View PDF Chat

Quasiparticle and quasihole states of nuclei around<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">Ni</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>56</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>

2009-06-15

C. Barbieri , M. Hjorth‐Jensen

View PDF Chat

Ab initioself-consistent Gorkov-Green's function calculations of semi-magic nuclei: Numerical implementation at second order with a two-nucleon interaction

2014-02-28

V. Somà , C. Barbieri , T. Duguet

View PDF Chat

Faddeev description of two-hole–one-particle motion and the single-particle spectral function

2001-02-20

C. Barbieri , W. H. Dickhoff

View PDF Chat

Accurate nuclear radii and binding energies from a chiral interaction

2015-05-01

A. Ekström , G. R. Jansen , Kyle Wendt +7 more

With the goal of developing predictive ab initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering … With the goal of developing predictive ab initio capability for light and medium-mass nuclei, two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named ${\mathrm{NNLO}}_{\mathrm{sat}}$, yield accurate binding energies and radii of nuclei up to $^{40}\mathrm{Ca}$, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective ${J}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$ states in $^{16}\mathrm{O}$ and $^{40}\mathrm{Ca}$ are described accurately, while spectra for selected $p$- and $sd$-shell nuclei are in reasonable agreement with experiment.

View PDF Chat

Accurate charge-dependent nucleon-nucleon potential at fourth order of chiral perturbation theory

2003-10-31

D. R. Entem , R. Machleidt

We present the first nucleon-nucleon potential at next-to-next-to-next-to-leading order (fourth order) of chiral perturbation theory. Charge dependence is included up to next-to-leading order of the isospin-violation scheme. The accuracy for … We present the first nucleon-nucleon potential at next-to-next-to-next-to-leading order (fourth order) of chiral perturbation theory. Charge dependence is included up to next-to-leading order of the isospin-violation scheme. The accuracy for the reproduction of the nucleon-nucleon $(NN)$ data below $290\text{\ensuremath{-}}\text{MeV}$ lab energy is comparable to the one of phenomenological high-precision potentials. Since $NN$ potentials of order three and less are known to be deficient in quantitative terms, the present work shows that the fourth order is necessary and sufficient for a $NN$ potential reliable up to $290\phantom{\rule{0.3em}{0ex}}\text{MeV}$. The new potential provides a promising starting point for exact few-body calculations and microscopic nuclear structure theory (including chiral many-body forces derived on the same footing).

View PDF Chat

Quasiparticles in neon using the Faddeev random-phase approximation

2007-11-06

C. Barbieri , Dimitri Van Neck , W. H. Dickhoff

View PDF Chat

Self-consistent Green's functions formalism with three-body interactions

2013-11-27

Arianna Carbone , Andrea Cipollone , C. Barbieri +2 more

View PDF Chat

Isotopic Chains Around Oxygen from Evolved Chiral Two- and Three-Nucleon Interactions

2013-08-07

Andrea Cipollone , C. Barbieri , P. Navrátil

View PDF Chat

Faddeev treatment of long-range correlations and the one-hole spectral function of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>16</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:math>

2002-06-03

C. Barbieri , W. H. Dickhoff

View PDF Chat

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

2015-07-10

Andrea Cipollone , C. Barbieri , P. Navrátil

View PDF Chat

Ab initioGorkov-Green's function calculations of open-shell nuclei

2013-01-24

V. Somà , C. Barbieri , T. Duguet

View PDF Chat

Modern theory of nuclear forces

2009-12-21

E. Epelbaum , H.‐W. Hammer , Ulf-G. Meißner

Effective field theory allows for a systematic and model-independent derivation of the forces between nucleons in harmony with the symmetries of Quantum Chromodynamics. We review the foundations of this approach … Effective field theory allows for a systematic and model-independent derivation of the forces between nucleons in harmony with the symmetries of Quantum Chromodynamics. We review the foundations of this approach and discuss its application for light nuclei at various resolution scales. The extension of this approach to many-body systems is briefly sketched.

View PDF Chat

Chiral two- and three-nucleon forces along medium-mass isotope chains

2014-06-05

V. Somà , Andrea Cipollone , C. Barbieri +2 more

View PDF Chat

Role of Long-Range Correlations in the Quenching of Spectroscopic Factors

2009-11-09

C. Barbieri

View PDF Chat

Improved nuclear matter calculations from chiral low-momentum interactions

2011-03-07

K. Hebeler , S. K. Bogner , R. J. Furnstahl +2 more

We present nuclear matter calculations based on low-momentum interactions derived from chiral effective field theory potentials. The current calculations use an improved treatment of the three-nucleon force (3NF) contribution that … We present nuclear matter calculations based on low-momentum interactions derived from chiral effective field theory potentials. The current calculations use an improved treatment of the three-nucleon force (3NF) contribution that includes a corrected combinatorial factor beyond Hartree-Fock that was omitted in previous nuclear matter calculations. We find realistic saturation properties using parameters fit only to few-body data, but with larger uncertainty estimates from cutoff dependence and the 3NF parametrization than in previous calculations.

View PDF Chat

Extension of the random phase approximation including the self-consistent coupling to two-phonon contributions

2003-07-29

C. Barbieri , W. H. Dickhoff

View PDF Chat

Nucleon-nucleus optical potential in the particle-hole approach

2005-07-29

C. Barbieri , B.K. Jennings

View PDF Chat

Radii and Binding Energies in Oxygen Isotopes: A Challenge for Nuclear Forces

2016-07-27

V. Lapoux , V. Somà , C. Barbieri +3 more

View PDF Chat

Medium-Mass Nuclei with Normal-Ordered Chiral<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi><mml:mi>N</mml:mi><mml:mo mathvariant="bold">+</mml:mo><mml:mn>3</mml:mn><mml:mi>N</mml:mi></mml:math>Interactions

2012-07-31

Robert Roth , Sven Binder , Klaus Vobig +3 more

We study the use of truncated normal-ordered three-nucleon interactions in nuclear structure calculations starting from chiral two- plus three-nucleon Hamiltonians evolved consistently with the similarity renormalization group. We present three … We study the use of truncated normal-ordered three-nucleon interactions in nuclear structure calculations starting from chiral two- plus three-nucleon Hamiltonians evolved consistently with the similarity renormalization group. We present three key developments: (i) a rigorous benchmark of the normal-ordering approximation in the importance-truncated no-core shell model for $^{4}\mathrm{He}$, $^{16}\mathrm{O}$, and $^{40}\mathrm{Ca}$; (ii) a direct comparison of the importance-truncated no-core shell model results with coupled-cluster calculations at the singles and doubles level for $^{16}\mathrm{O}$; and (iii) first applications of similarity renormalization group-evolved chiral $NN+3N$ Hamiltonians in coupled-cluster calculations for medium-mass nuclei $^{16,24}\mathrm{O}$ and $^{40,48}\mathrm{Ca}$. We show that the normal-ordered two-body approximation works very well beyond the lightest isotopes and opens a path for studies of medium-mass and heavy nuclei with chiral two- plus three-nucleon interactions. At the same time we highlight the predictive power of chiral Hamiltonians.

View PDF Chat

Single particle spectra based on modern effective interactions

2006-11-08

C. Barbieri

View PDF Chat

Unexpectedly large charge radii of neutron-rich calcium isotopes

2016-02-08

R. F. García Ruíz , M. L. Bissell , K. Blaum +7 more

View PDF Chat

Momentum and energy distributions of nucleons in finite nuclei due to short-range correlations

1995-06-01

H. Müther , A. Polls , W. H. Dickhoff

The influence of short-range correlations on the momentum and energy distribution of nucleons in nuclei is evaluated assuming a realistic meson-exchange potential for the nucleon-nucleon interaction. Using the Green-function approach … The influence of short-range correlations on the momentum and energy distribution of nucleons in nuclei is evaluated assuming a realistic meson-exchange potential for the nucleon-nucleon interaction. Using the Green-function approach the calculations are performed directly for the finite nucleus $^{16}$O avoiding the local density approximation and its reference to studies of infinite nuclear matter. The nucleon-nucleon correlations induced by the short-range and tensor components of the interaction yield an enhancement of the momentum distribution at high momenta as compared to the Hartree-Fock description. These high-momentum components should be observed mainly in nucleon knockout reactions like $(e,e'p)$ leaving the final nucleus in a state of high excitation energy. Our analysis also demonstrates that non-negligible contributions to the momentum distribution should be found in partial waves which are unoccupied in the simple shell-model. The treatment of correlations beyond the Brueckner-Hartree-Fock approximation also yields an improvement for the calculated ground-state properties.

View PDF Chat

Self-Consistent Green's Function Theory for Atomic Nuclei

2020-09-24

V. Somà

Nuclear structure theory has recently gone through a major renewal with the development of ab initio techniques that can be applied to a large number of atomic nuclei, well beyond … Nuclear structure theory has recently gone through a major renewal with the development of ab initio techniques that can be applied to a large number of atomic nuclei, well beyond the light sector that had been traditionally targeted in the past. Self-consistent Green's function theory is one among these techniques. The present work aims to give an overview of the self-consistent Green's function approach for atomic nuclei, including examples of recent applications and a discussion on the perspectives for extending the method to nuclear reactions, doubly open-shell systems and heavy nuclei.

View PDF Chat

Algebraic diagrammatic construction formalism with three-body interactions

2018-05-08

Francesco Raimondi , C. Barbieri

View PDF Chat

Microscopic self-energy calculations and dispersive optical-model potentials

2011-09-29

S. J. Waldecker , C. Barbieri , W. H. Dickhoff

View PDF Chat

Novel chiral Hamiltonian and observables in light and medium-mass nuclei

2020-01-22

V. Somà , P. Navrátil , Francesco Raimondi +2 more

View PDF Chat

From low-momentum interactions to nuclear structure

2010-03-09

S. K. Bogner , R. J. Furnstahl , A. Schwenk

View PDF Chat

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

2019-08-26

A. Idini , C. Barbieri , P. Navrátil

View PDF Chat

Neutron and weak-charge distributions of the 48Ca nucleus

2015-11-02

G. Hagen , A. Ekström , C. Forssén +7 more

View PDF Chat

Ab Initio Computation of Charge Densities for Sn and Xe Isotopes

2020-10-28

P. Arthuis , C. Barbieri , Matteo Vorabbi +1 more

View PDF Chat

In-Medium Similarity Renormalization Group For Nuclei

2011-06-01

Koshiroh Tsukiyama , S. K. Bogner , A. Schwenk

We present a new ab initio method that uses similarity renormalization group (SRG) techniques to continuously diagonalize nuclear many-body Hamiltonians. In contrast with applications of the SRG to two- and … We present a new ab initio method that uses similarity renormalization group (SRG) techniques to continuously diagonalize nuclear many-body Hamiltonians. In contrast with applications of the SRG to two- and three-nucleon interactions in free space, we perform the SRG evolution "in medium" directly in the A-body system of interest. The in-medium approach has the advantage that one can approximately evolve 3,…,A-body operators using only two-body machinery based on normal-ordering techniques. The method is nonperturbative and can be tailored to problems ranging from the diagonalization of closed-shell nuclei to the construction of effective valence-shell Hamiltonians and operators. We present first results for the energies of 4He, 16O, and 40Ca, which have accuracies comparable to coupled-cluster calculations.

View PDF Chat

Chiral effective field theory and nuclear forces

2011-02-20

R. Machleidt , D. R. Entem

View PDF Chat

Asymmetry Dependence of Proton Correlations

2006-10-17

R. J. Charity , L. G. Sobotka , W. H. Dickhoff

A dispersive-optical-model analysis of $p+^{40}\mathrm{Ca}$ and $p+^{48}\mathrm{Ca}$ interactions has been carried out. The real and imaginary potentials have been constrained from fits to elastic-scattering data, reaction cross sections, and level … A dispersive-optical-model analysis of $p+^{40}\mathrm{Ca}$ and $p+^{48}\mathrm{Ca}$ interactions has been carried out. The real and imaginary potentials have been constrained from fits to elastic-scattering data, reaction cross sections, and level properties of valence hole states deduced from ($e$, ${e}^{\ensuremath{'}}p$) data. The surface imaginary potential was found to be larger overall and the gap in this potential on either side of the Fermi energy was found to be smaller for the neutron-rich $p+^{48}\mathrm{Ca}$ system. These results imply that protons with energies near the Fermi surface experience larger correlations with increasing asymmetry.

View PDF Chat

Effects of nuclear correlations on the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">O</mml:mi><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>16</mml:mn></mml:mrow></mml:mmultiscripts><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mi>e</mml:mi><mml:mo>,</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mi>p</mml:mi><mml:mi>N</mml:mi></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math…

2004-07-14

C. Barbieri , C. Giusti , F. D. Pacati +1 more

View PDF Chat

Self-Consistent Green’s Function Approaches

2017-01-01

C. Barbieri , Arianna Carbone

View PDF Chat

Ab InitioCalculations of Even Oxygen Isotopes with Chiral Two-Plus-Three-Nucleon Interactions

2013-06-10

H. Hergert , Sven Binder , Angelo Calci +2 more

We formulate the in-medium similarity renormalization group (IM-SRG) for open-shell nuclei using a multireference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multireference IM-SRG (MR-IM-SRG) … We formulate the in-medium similarity renormalization group (IM-SRG) for open-shell nuclei using a multireference formalism based on a generalized Wick theorem introduced in quantum chemistry. The resulting multireference IM-SRG (MR-IM-SRG) is used to perform the first ab initio study of all even oxygen isotopes with chiral nucleon-nucleon and three-nucleon interactions, from the proton to the neutron drip lines. We obtain an excellent reproduction of experimental ground-state energies with quantified uncertainties, which is validated by results from the importance-truncated no-core shell model and the coupled cluster method. The agreement between conceptually different many-body approaches and experiment highlights the predictive power of current chiral two- and three-nucleon interactions, and establishes the MR-IM-SRG as a promising new tool for ab initio calculations of medium-mass nuclei far from shell closures.

View PDF Chat

Three-Body Forces and the Limit of Oxygen Isotopes

2010-07-13

Takaharu Otsuka , Toshio Suzuki , J. D. Holt +2 more

The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced … The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from (28)O to the experimentally observed (24)O. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments.

View PDF Chat

Correlated Strength in the Nuclear Spectral Function

2004-10-25

D. Rohe , Christopher Armstrong , R. Asaturyan +7 more

We have carried out an (e,e′p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k … We have carried out an (e,e′p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment locates by direct measurement the correlated strength predicted by theory.Received 18 May 2004DOI:https://doi.org/10.1103/PhysRevLett.93.182501©2004 American Physical Society

View PDF Chat

Accurate nucleon-nucleon potential with charge-independence breaking

1995-01-01

R. B. Wiringa , V. G. J. Stoks , R. Schiavilla

We present a new high-quality nucleon-nucleon potential with explicit charge dependence and charge asymmetry, which we designate Argonne ${\mathit{v}}_{18}$. The model has a charge-independent part with 14 operator components that … We present a new high-quality nucleon-nucleon potential with explicit charge dependence and charge asymmetry, which we designate Argonne ${\mathit{v}}_{18}$. The model has a charge-independent part with 14 operator components that is an updated version of the Argonne ${\mathit{v}}_{14}$ potential. Three additional charge-dependent and one charge-asymmetric operators are added, along with a complete electromagnetic interaction. The potential has been fit directly to the Nijmegen pp and np scattering database, low-energy nn scattering parameters, and deuteron binding energy. With 40 adjustable parameters it gives a ${\mathrm{\ensuremath{\chi}}}^{2}$ per datum of 1.09 for 4301 pp and np data in the range 0--350 MeV.

View PDF Chat

Nonperturbative Shell-Model Interactions from the In-Medium Similarity Renormalization Group

2014-10-03

S. K. Bogner , H. Hergert , J. D. Holt +5 more

We present the first ab initio construction of valence-space Hamiltonians for medium-mass nuclei based on chiral two- and three-nucleon interactions using the in-medium similarity renormalization group. When applied to the … We present the first ab initio construction of valence-space Hamiltonians for medium-mass nuclei based on chiral two- and three-nucleon interactions using the in-medium similarity renormalization group. When applied to the oxygen isotopes, we find experimental ground-state energies are well reproduced, including the flat trend beyond the drip line at (24)O. Similarly, natural-parity spectra in (21,22,23,24)O are in agreement with experiment, and we present predictions for excited states in (25,26)O. The results exhibit a weak dependence on the harmonic-oscillator basis parameter and reproduce spectroscopy within the standard sd valence space.

View PDF Chat

Effects of rescattering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>e</mml:mi><mml:mo>,</mml:mo><mml:msup><mml:mi>e</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:mi>p</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>reactions within a semiclassical model

2004-11-24

C. Barbieri , L. Lapikás

View PDF Chat

Single-particle spectral function of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>16</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>

1994-01-01

H. Müther , W. H. Dickhoff

The influence of short-range correlations on the p-wave single-particle spectral function in $^{16}\mathrm{O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum … The influence of short-range correlations on the p-wave single-particle spectral function in $^{16}\mathrm{O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum components, is found to be small in the p-shell quasihole wave functions. It is therefore unlikely that studies of quasihole momentum distributions using the (e,e'p) reaction will reveal a significant contribution of high-momentum components. Instead, high-momentum components become increasingly more dominant at higher excitation energy. The above observations are consistent with the energy distribution of high-momentum components in nuclear matter.

View PDF Chat

Evolution of Shell Structure in Neutron-Rich Calcium Isotopes

2012-07-17

G. Hagen , M. Hjorth‐Jensen , G. R. Jansen +2 more

We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically … We employ interactions from chiral effective field theory and compute the binding energies and low-lying excitations of calcium isotopes with the coupled-cluster method. Effects of three-nucleon forces are included phenomenologically as in-medium two-nucleon interactions, and the coupling to the particle continuum is taken into account using a Berggren basis. The computed ground-state energies and the low-lying ${J}^{\ensuremath{\pi}}={2}^{+}$ states for the isotopes $^{42,48,50,52}\mathrm{Ca}$ are in good agreement with data, and we predict the excitation energy of the first ${J}^{\ensuremath{\pi}}={2}^{+}$ state in $^{54}\mathrm{Ca}$ at 1.9 MeV, displaying only a weak subshell closure. In the odd-mass nuclei $^{53,55,61}\mathrm{Ca}$ we find that the positive parity states deviate strongly from the naive shell model.

View PDF Chat

Ab initio path to heavy nuclei

2014-07-09

Sven Binder , Joachim Langhammer , Angelo Calci +1 more

We present the first ab initio calculations of nuclear ground states up into the domain of heavy nuclei, spanning the range from 16-O to 132-Sn based on two- plus three-nucleon … We present the first ab initio calculations of nuclear ground states up into the domain of heavy nuclei, spanning the range from 16-O to 132-Sn based on two- plus three-nucleon interactions derived within chiral effective field theory. We employ the similarity renormalization group for preparing the Hamiltonian and use coupled-cluster theory to solve the many-body problem for nuclei with closed sub-shells. Through an analysis of theoretical uncertainties resulting from various truncations in this framework, we identify and eliminate the technical hurdles that previously inhibited the step beyond medium-mass nuclei, allowing for reliable validations of nuclear Hamiltonians in the heavy regime. Following this path we show that chiral Hamiltonians qualitatively reproduce the systematics of nuclear ground-state energies up to the neutron-rich Sn isotopes.

View PDF Chat

In-medium<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:math>matrix for nuclear matter with three-body forces: Binding energy and single-particle properties

2008-11-26

V. Somà , Piotr Bożek

We present spectral calculations of nuclear matter properties including three-body forces. Within the in-medium $T$-matrix approach, implemented with the CD-Bonn and Nijmegen potentials plus the three-nucleon Urbana interaction, we compute … We present spectral calculations of nuclear matter properties including three-body forces. Within the in-medium $T$-matrix approach, implemented with the CD-Bonn and Nijmegen potentials plus the three-nucleon Urbana interaction, we compute the energy per particle in symmetric and neutron matter. The three-body forces are included via an effective density dependent two-body force in the in-medium $T$-matrix equations. After fine tuning the parameters of the three-body force to reproduce the phenomenological saturation point in symmetric nuclear matter, we calculate the incompressibility and the energy per particle in neutron matter. We find a soft equation of state in symmetric nuclear matter but a relatively large value of the symmetry energy. We study the the influence of the three-body forces on the single-particle properties. For symmetric matter the spectral function is broadened at all momenta and all densities, while an opposite effect is found for the case of neutrons only. Noticeable modification of the spectral functions are realized only for densities above the saturation density. The modifications of the self-energy and the effective mass are not very large and appear to be strongly suppressed above the Fermi momentum.

View PDF Chat

Faddeev random-phase approximation for molecules

2011-04-27

Matthias Degroote , Dimitri Van Neck , C. Barbieri

View PDF Chat

Ab initio calculation of the potential bubble nucleus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi mathvariant="normal">Si</mml:mi><mml:mprescripts /><mml:none /><mml:mn>34</mml:mn></mml:mmultiscripts></mml:math>

2017-03-23

T. Duguet , V. Somà , S. Lecluse +2 more

View PDF Chat

Ab initiomultireference in-medium similarity renormalization group calculations of even calcium and nickel isotopes

2014-10-23

H. Hergert , S. K. Bogner , Titus Morris +4 more

We use the newly developed multireference in-medium similarity renormalization group to study all even isotopes of the calcium and nickel isotopic chains, based on two- plus three-nucleon interactions derived from … We use the newly developed multireference in-medium similarity renormalization group to study all even isotopes of the calcium and nickel isotopic chains, based on two- plus three-nucleon interactions derived from chiral effective field theory. We present results for ground-state and two-neutron separation energies and quantify their theoretical uncertainties. At shell closures, we find excellent agreement with coupled-cluster results obtained with the same Hamiltonians. Our results confirm the importance of chiral $3N$ interactions to obtain a correct reproduction of experimental energy trends, and their subtle impact in neutron-rich Ca and Ni isotopes. At the same time, we uncover and discuss deficiencies of the input Hamiltonians which need to be addressed by the next generation of chiral interactions.

View PDF Chat