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 measurement of $p_\mathrm{T}$-differential elliptic flow ($v_{2}$) coefficient for inclusive charged hadrons as well as a variety of identified particle species in p--Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV recorded by ALICE during the LHC Run 2 data taking are presented. Besides high precision measurements of $v_2(p_\mathrm{T})$ for $\mathrm{π^\pm, K^\pm}$ and $\mathrm{p(\bar{p})}$, the very first results for $\mathrm{K_{S}^{0}, Λ(\barΛ)}$ 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 $\sqrt{s}=13$ TeV. Moreover, reported characteristic mass ordering and approximate NCQ and $\mathrm{KE_T}$ scaling of $v_{2}$ allows to test various theoretical models, constrain the initial conditions, and probe the origin of collective behavior in small collision systems.