Measurement of the relative yields of $\psi(2S)$ to $\psi(1S)$ mesons   produced at forward and backward rapidity in $p$$+$$p$, $p$$+$Al, $p$$+$Au,   and $^{3}$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV
  The PHENIX Collaboration has measured the ratio of the yields of $\psi(2S)$ to $\psi(1S)$ mesons produced in $p$$+$$p$, $p$$+$Al, $p$$+$Au, and $^{3}$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ 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 $^{3}$He-going) direction, the relative yield of $\psi(2S)$ mesons to $\psi(1S)$ mesons is consistent with the value measured in \pp collisions. However, in the backward (nucleus-going) direction, the $\psi(2S)$ is preferentially suppressed by a factor of $\sim$2. This suppression is attributed in some models to breakup of the weakly-bound $\psi(2S)$ 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. 
A. Adare, C. Aidala, N.N. Ajitanand, Y. Akiba, M. Alfred, V. Andrieux,   K. Aoki, N. Apadula, H. Asano, C. Ayuso, B. Azmoun,...
nucl-ex