$\Upsilon$ production and nuclear modification at forward rapidity in Pb-Pb collisions at $\mathbf{\sqrt{\textit{s}_{\textbf{NN}}}=5.02}$ TeV

TL;DR

This paper reports on the measurement of $$ production in Pb-Pb collisions at 5.02 TeV, showing suppression of excited states and comparing results with various theoretical models to understand quarkonium behavior in quark-gluon plasma.

Contribution

First measurement of $$ meson suppression at forward rapidity in Pb-Pb collisions at 5.02 TeV, including the observation of $2$ signals and comparison with multiple models.

Findings

$1$ meson suppressed by factor of three compared to pp collisions.

First observation of $2$ meson at forward rapidity with significant suppression.

Results consistent with models predicting quarkonium suppression in quark-gluon plasma.

Abstract

The production of $\Upsilon$ mesons in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}$ = 5 TeV is measured with the muon spectrometer of the ALICE detector at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region $2.5<y<4.0$, as a function of rapidity, transverse momentum and collision centrality. The results show that the production of the $\Upsilon$(1S) meson is suppressed by a factor of about three with respect to the production in proton-proton collisions. For the first time, a significant signal for the $\Upsilon$(2S) meson is observed at forward rapidity, indicating a suppression stronger by about a factor 2-3 with respect to the ground state. The measurements are compared with transport, hydrodynamic, comover and statistical hadronisation model calculations.