Strange hadron collectivity in pPb and PbPb collisions

TL;DR

This paper investigates the collective behavior of strange hadrons in pPb and PbPb collisions at the LHC by measuring their elliptic flow ($v_2$) using advanced correlation methods, revealing insights into system size effects.

Contribution

It provides the first detailed comparison of strange hadron elliptic flow in pPb and PbPb collisions, highlighting the role of system size and flow fluctuations.

Findings

Strange hadron $v_2$ values are nearly identical in pPb and PbPb collisions.

Event-by-event flow fluctuations depend on system size.

Nonflow effects are minimized using subevent cumulant analysis.

Abstract

The collective behavior of K$^0_\mathrm{S}$ and $\Lambda/\bar{\Lambda}$ strange hadrons is studied by measuring the elliptic azimuthal anisotropy ($v_2$) using the scalar-product and multiparticle correlation methods. Proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV and lead-lead (PbPb) collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV collected by the CMS experiment at the LHC are investigated. Nonflow effects in the pPb collisions are studied by using a subevent cumulant analysis and by excluding events where a jet with transverse momentum greater than 20\GeV is present. The strange hadron $v_2$ values extracted in \pPb collisions via the four- and six-particle correlation method are found to be nearly identical, suggesting the collective behavior. Comparisons of the pPb and PbPb results for both strange hadrons and charged particles illustrate how event-by-event flow fluctuations depend on the system size.