Centrality determination in heavy-ion collisions with the LHCb detector

TL;DR

This paper presents a method for determining collision centrality in heavy-ion experiments using the LHCb detector, applicable to lead-lead and lead-neon collisions, with results aligning with previous experiments and pioneering fixed-target measurements.

Contribution

The paper introduces a new procedure for centrality determination in heavy-ion collisions at LHCb, including the first fixed-target centrality measurements at the LHC.

Findings

Good agreement with other experiments for lead-lead collisions

First centrality measurements in lead-neon fixed-target collisions at the LHC

Centrality classes derived from electromagnetic calorimeter energy deposits

Abstract

The centrality of heavy-ion collisions is directly related to the medium created therein. A procedure to determine the centrality of collisions with the LHCb detector is implemented for lead-lead collisions at $\sqrt{s_{\scriptscriptstyle\text{NN}}}=5\, \mathrm{TeV}$ and lead-neon fixed-target collisions at $\sqrt{s_{\scriptscriptstyle\text{NN}}}=69\, \mathrm{GeV}$. The energy deposits in the electromagnetic calorimeter are used to determine and define the centrality classes. The correspondence between the number of participants and the centrality for the lead-lead collisions is in good agreement with the correspondence found in other experiments, and the centrality measurements for the lead-neon collisions presented here are the first performed in fixed-target collisions at the LHC.