$\Upsilon$ suppression at forward rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV

TL;DR

This study measures the suppression of $
$ mesons in lead-lead collisions at the LHC, revealing increased suppression with collision centrality and providing insights into quark-gluon plasma effects.

Contribution

First measurement of $
$ and $$ suppression at 5.02 TeV in Pb-Pb collisions across various centralities, transverse momentum, and rapidity ranges.

Findings

$
$ suppression increases with collision centrality.

$
$ suppression is consistent across transverse momentum and rapidity.

The $
$ to $$ suppression ratio is approximately 0.28.

Abstract

Inclusive $\Upsilon$(1S) and $\Upsilon$(2S) production have been measured in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{_{\rm NN}}}=5.02$ TeV, using the ALICE detector at the CERN LHC. The $\Upsilon$ mesons are reconstructed in the centre-of-mass rapidity interval $2.5<y<4$ and in the transverse-momentum range $p_{\rm T}<15$ GeV/$c$, via their decays to muon pairs. In this Letter, we present results on the inclusive $\Upsilon$(1S) nuclear modification factor $R_{\rm AA}$ as a function of collision centrality, transverse momentum and rapidity. The $\Upsilon$(1S) and $\Upsilon$(2S) $R_{\rm AA}$, integrated over the centrality range 0-90%, are $0.37 \pm 0.02 {\rm{(stat)}}\pm 0.03 {\rm{(syst)}}$ and $0.10 \pm 0.04 {\rm{(stat)}}\pm 0.02 {\rm{(syst)}}$, respectively, leading to a ratio $R_{\rm{AA}}^{\Upsilon(\rm2S)}/R_{\rm{AA}}^{\Upsilon(\rm1S)}$ of $0.28\pm0.12\text{(stat)}\pm0.06\text{(syst)}$. The observed $\Upsilon$(1S) suppression increases with the centrality of the collision and no significant variation is observed as a function of transverse momentum and rapidity.