Type: Article
Publication Date: 2017-03-09
Citations: 33
DOI: https://doi.org/10.1103/physrevc.95.034904
The PHENIX Collaboration has measured the ratio of the yields of $\ensuremath{\psi}(2S)$ to $\ensuremath{\psi}(1S)$ mesons produced in $p+p$, $p+\mathrm{Al}$, $p+\mathrm{Au}$, and $^{3}\mathrm{He}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{\mathit{NN}}}}=200$ GeV over the forward and backward rapidity intervals $1.2<|y|<2.2$. We find that the ratio in $p+p$ collisions is consistent with measurements at other collision energies. In collisions with nuclei, we find that in the forward ($p$-going or $^{3}\mathrm{He}$-going) direction, the relative yield of $\ensuremath{\psi}(2S)$ mesons to $\ensuremath{\psi}(1S)$ mesons is consistent with the value measured in $p+p$ collisions. However, in the backward (nucleus-going) direction, the $\ensuremath{\psi}(2S)$ meson is preferentially suppressed by a factor of $\ensuremath{\sim}2$. This suppression is attributed in some models to the breakup of the weakly bound $\ensuremath{\psi}(2S)$ meson through final-state interactions with comoving particles, which have a higher density in the nucleus-going direction. These breakup effects may compete with color screening in a deconfined quark-gluon plasma to produce sequential suppression of excited quarkonia states.