# Suppression of excited $\Upsilon$ states relative to the ground state in PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV

## TL;DR

This study measures the suppression of excited $$ states relative to the ground state in PbPb collisions at 5.02 TeV, revealing significant suppression especially for the $$(3S) state, with no strong dependence on collision parameters.

## Contribution

First measurement of double ratios of $$ meson states in PbPb versus pp collisions at 5.02 TeV, demonstrating suppression of excited states in heavy-ion collisions.

## Key findings

- Double ratios for $$(2S) and $$(3S) are significantly below 1.
- No significant $$(3S) signal observed in PbPb collisions.
- Suppression does not strongly depend on collision centrality, transverse momentum, or rapidity.

## Abstract

The relative yields of $\Upsilon$ mesons produced in pp and PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ratios are formed by comparing the yields of the excited states, $\Upsilon$(2S) and $\Upsilon$(3S), to the ground state, $\Upsilon$(1S), in both PbPb and pp collisions at the same center-of-mass energy. The double ratios, [$\Upsilon$(nS)/$\Upsilon$(1S)]$_\mathrm{PbPb}$ / [$\Upsilon$(nS)/$\Upsilon$(1S)]$_\mathrm{pp}$, are measured to be 0.308 $\pm$ 0.055 (stat) $\pm$ 0.019 (syst) for the $\Upsilon$(2S) and less than 0.26 at 95% confidence level for the $\Upsilon$(3S). No significant $\Upsilon$(3S) signal is found in the PbPb data. The double ratios are studied as a function of collision centrality, as well as dimuon transverse momentum and rapidity. No significant dependencies are observed.