Evidence for similar collectivity of high transverse momentum particles in pPb and PbPb collisions

TL;DR

This study compares the elliptic flow ($v_2$) of high transverse momentum particles in proton-lead and lead-lead collisions, revealing similar collective behavior and suggesting a common origin for multi-particle collectivity in both systems.

Contribution

It provides the first direct comparison of high-$p_T$ elliptic flow in pPb and PbPb collisions using four-particle cumulants, indicating similar collectivity at high $p_T$.

Findings

Significant positive $v_2$ at high $p_T$ in both systems.

Similar $v_2$ values at comparable multiplicities.

Evidence for common multi-particle collectivity origin.

Abstract

Charged hadron elliptic anisotropies ($v_2$) are presented over a wide transverse momentum ($p_\text{T}$) range for proton-lead (pPb) and lead-lead (PbPb) collisions at nucleon-nucleon center-of-mass energies of 8.16 and 5.02 TeV, respectively. The data were recorded by the CMS experiment and correspond to integrated luminosities of 186 nb$^{-1}$ and 0.607 nb$^{-1}$ for the pPb and PbPb systems, respectively. A four-particle cumulant analysis is performed using subevents separated in pseudorapidity to effectively suppress non-collective effects. At high $p_\text{T}$ ($p_\text{T}$ $\gt$ 8 GeV), significant positive $v_2$ values are observed that are similar between pPb and PbPb collisions at comparable charged particle multiplicities. This observation suggests a common origin for the multi-particle collectivity for high-$p_\text{T}$ particles in the two systems.