The fate of the weakly-bound $\psi(2s)$ in nuclear matter

TL;DR

This paper reports on the suppression of $ ext{psi}(2s)$ in nuclear collisions at RHIC, revealing unexpected suppression patterns that challenge existing models, and presents new measurements enabled by upgraded detector technology.

Contribution

It provides the first separation of $ ext{psi}(2s)$ from $J/ ext{psi}$ at RHIC and compares suppression in $d+$Au and $p+p$ collisions at different energies.

Findings

Strong $ ext{psi}(2s)$ suppression relative to $J/ ext{psi}$ in $d+$Au collisions.

Suppression cannot be explained by nuclear breakup effects alone.

First measurement of $ ext{psi}(2s)$ production in $p+p$ at 510 GeV.

Abstract

We present new results of a completed PHENIX analysis of $\psi(2s)$ modification at midrapidity in 200 GeV $d+$Au collisions. Strong suppression of the $\psi(2s)$ relative to the $J/\psi$ is observed. This difference in suppression is too strong to be explained by breakup effects in the nucleus, due to the short nuclear crossing times at RHIC. Given the observation of long range correlations in $p(d)+$A collisions at LHC and RHIC, consistent with hydrodynamics, these observations raise interesting questions about the mechanism of $\psi(2s)$ suppression when it is produced in a nuclear target. In 2012, the PHENIX Collaboration installed the FVTX, a silicon tracker that precisely measures muon pair opening angles prior to any multiple scattering in the muon arm absorber, and thus provides an improved dimuon mass resolution. The FVTX allows the $\psi(2s)$ to be separated from the $J/\psi$ at forward and backward rapidity for the first time at RHIC. We present new results on $\psi(2s)$ production in $p+p$ collisions at $\sqrt{s} = 510$ GeV from the 2013 data set.