Azimuthal anisotropy of charged particles with transverse momentum up to 100GeV/c in PbPb collisions at √sNN = 5.02TeV

The Fourier coefficients v_2 and v_3 characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at √sNN = 5.02TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, 1 〈 p_T 〈 100GeV/c. The analysis focuses on the p_T 〉 10GeV/c 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 initial-state fluctuations. The values from both methods remain positive up to p_T ~ 60-80GeV/c, in all examined centrality classes. The v_3 coefficient, only measured with the scalar product method, tends to zero for p_T ≳ 20GeV/c. 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