Observation of the "K- pp"-like structure in the d( +, K+) reaction at 1.69 GeV/c

Y. Ichikawa, T. Nagae, Hiroyuki Fujioka, H. Bhang, S. Bufalino, H. Ekawa, P. Evtoukhovitch, A. Feliciello, S. Hasegawa, S. Hayakawa

Abstract

We have observed a “|$K^{-}pp$|”-like structure in the |$d(\pi ^{+ },K^{+ })$| reaction at 1.69 GeV|$/c$|⁠. In this reaction, a |$\Lambda (1405)$| hyperon resonance is expected to be produced as a doorway to form |$K^{-}pp$| through the |$\Lambda ^{\ast }p\rightarrow K^{-}pp$| process. However, most of the |$\Lambda (1405)$| produced would escape from the deuteron without secondary reactions. Therefore, coincidence of high-momentum (⁠|$>$|250 MeV|$/c$|⁠) proton(s) at large emission angles (⁠|$39^\circ \lt \theta _{\rm lab.} \lt 122^\circ$|⁠) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra is observed around the missing mass of 2.27 GeV|$/c^2$|⁠, which corresponds to the |$K^{-}pp$| binding energy of 95 |${}^{+18}_{-17}$| (stat.) |${}^{+30}_{-21}$| (syst.) MeV and the width of 162 |${}^{+87}_{-45}$| (stat.) |${}^{+66}_{-78}$| (syst.) MeV.

Locations

• Progress of Theoretical and Experimental Physics - View - PDF
• arXiv (Cornell University) - View - PDF
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