# Azimuthal anisotropy of charged particles with transverse momentum up to 100 GeV in PbPb collisions at sqrt(s[NN]) = 5.02 TeV

## TL;DR

This paper measures azimuthal anisotropy coefficients v2 and v3 of charged particles in PbPb collisions at 5.02 TeV across a wide transverse momentum range, providing insights into parton energy loss and initial-state fluctuations.

## Contribution

It presents the first detailed measurement of v2 and v3 at high pT up to 100 GeV in PbPb collisions, comparing different analysis methods and constraining theoretical models.

## Key findings

- v2 remains positive up to 60-80 GeV across centralities
- v3 tends to zero for pT ≥ 20 GeV
- Results constrain models of parton energy loss and initial fluctuations

## Abstract

The Fourier coefficients v[2] and v[3] characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at sqrt(s[NN]) = 5.02 TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, 1 < pT < 100 GeV. The analysis focuses on pT > 10 GeV range, where anisotropic azimuthal distributions should reflect the path-length dependence of parton energy loss in the created medium. Results are presented in several bins of PbPb collision centrality, spanning the 60% most central events. The v[2] coefficient is measured with the scalar product and the multiparticle cumulant methods, which have different sensitivities to the initial-state fluctuations. The values of both methods remain positive up to pT of about 60-80 GeV, in all examined centrality classes. The v[3] coefficient, only measured with the scalar product method, tends to zero for pT greater than or equal to 20 GeV. Comparisons between theoretical calculations and data provide new constraints on the path-length dependence of parton energy loss in heavy ion collisions and highlight the importance of the initial-state fluctuations.