Investigating the elliptic anisotropy of identified particles in p--Pb collisions with a multi-phase transport model

Abstract

The elliptic azimuthal anisotropy coefficient ($v_2$) of the identified particles at midrapidity ($|\eta |<0.8$) was investigated in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV using a multi-phase transport model (AMPT). The calculations of differential $v_2$ based on the advanced flow extraction method of light flavor hadrons (pions, kaons, protons, and $\Lambda$) in small collision systems were extended to a wider transverse momentum ($p_{\mathrm{T}}$) range of up to 8 GeV/$c$ for the first time. The string-melting version of the AMPT model provides a good description of the measured $p_{\mathrm{T}}$-differential $v_2$ of the mesons but exhibits a slight deviation from the baryon $v_2$. In addition, we observed the features of mass ordering at low $p_{\mathrm{T}}$ and the approximate number of constituent quarks (NCQ) scaled at intermediate $p_{\mathrm{T}}$. Moreover, we demonstrate that hadronic rescattering does not have a significant impact on $v_2$ in p--Pb collisions for different centrality selections, whereas partonic scattering dominates in generating the elliptic anisotropy of the final particles. This study provides further insight into the origin of collective-like behavior in small collision systems and has referential value for future measurements of azimuthal anisotropy.

Comments: 9 pages, 9 figures