Elliptic flow of identified hadrons in small collisional systems measured with ALICE

Abstract

Recent observations of long-range multi-particle azimuthal correlations in p–Pb and high multiplicity pp collisions provided new insights into collision dynamics and opened a possibility to study collective effects in these small systems. New measurements of pT-differential elliptic flow (v2) coefficient for inclusive charged hadrons as well as a variety of identified particle species in p–Pb collisions at √sNN = 5.02 TeV are presented. The data was collected by ALICE during the LHC Run 2 data taking. Besides high precision measurements of v2(pT) for π±, K± and p(p), the first ¯ results for K0 S, Λ(Λ¯ ) and φ are shown. In order to eliminate non-flow contamination, a pseudorapidity separation between correlated particles is applied as well as subtraction of remaining non-flow estimate based on a measurement of minimum-bias pp collisions at √s = 13 TeV. Moreover, the reported characteristic mass ordering and approximate number of constituent quarks (NCQ) and transverse kinetic energy (KET) scaling of v2 allow to test various theoretical models, constrain the initial conditions, and probe the origin of collective behavior in small collision systems.