Azimuthal anisotropy of charged particles with transverse momentum up to 100 GeV/c in PbPb collisions at s<inf>NN</inf>=5.02 TeV

Abstract

© 2017 The Author The Fourier coefficients v 2 and v 3 characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at s NN =5.02 TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, 1 < p T < 100 GeV/c. The analysis focuses on the p T > 10 GeV/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 ∼60–80 GeV/c, in all examined centrality classes. The v 3 coefficient, only measured with the scalar product method, tends to zero for p T ≳20 GeV/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.