# Hot-medium effects on $\Upsilon$ yields in pPb collisions at $\sqrt{s_\text{NN}}=8.16$ TeV

## TL;DR

This paper investigates the combined effects of cold nuclear matter and hot quark-gluon plasma on the suppression of $
$Upsilon mesons in pPb collisions at 8.16 TeV, highlighting the relevance of hot-medium effects despite the small initial fireball size.

## Contribution

It provides a detailed analysis of hot-medium effects on $
$Upsilon suppression in pPb collisions, incorporating both cold-matter and hot-medium contributions with comparison to recent LHC data.

## Key findings

- Hot-medium effects are significant in $
$Upsilon suppression.
- Cold-matter effects alone cannot explain the data.
- Initial fireball temperature is approximately 460 MeV.

## Abstract

The respective contributions of cold-matter and hot-medium effects to the suppression of $\Upsilon(1S)$ and $\Upsilon(2S)$ mesons in pPb collisions at energies reached at the Large Hadron Collider (LHC) are investigated. Whereas known alterations of the parton density functions in the lead nucleus and coherent parton energy loss account for the leading fraction of the modifications in cold nuclear matter (CNM), the hot-medium (quark-gluon plasma, QGP) effects turn out to be relevant in spite of the small initial spatial extent of the fireball. We compare our transverse-momentum-, rapidity-, and centrality-dependent theoretical results for the $\Upsilon$ suppression in pPb collisions at a center-of-mass energy of $\sqrt{s_\text{NN}} = 8.16$ TeV with recent LHCb and preliminary ALICE data from the Large Hadron Collider (LHC). Both cold-matter and hot-medium effects are needed to account for the data. The initial central temperature of the fireball is found to be $T_0 \simeq 460$ MeV.