Investigating the role of partonic and hadronic dynamics in mass splitting of elliptic anisotropy in $p$-Pb collisions at $\sqrt{{s}_{NN}}=5.02$ TeV

Investigating the role of partonic and hadronic dynamics in mass splitting of elliptic anisotropy in $p$ -Pb collisions at $\sqrt{s_{N N}} = 5.02$ TeV

Debojit Sarkar, Subikash Choudhury, and Subhasis Chattopadhyay

Phys. Rev. C 94, 044919 – Published 31 October 2016

Abstract

The mass ordering of $v_{2}^{hadron}$ is regarded as one of the key signatures of collective behavior in ultrarelativistic heavy ion collisions. This observation has been found to be in compliance with the hydrodynamical response of a strongly interacting system to the initial spatial anisotropy. Flow coefficients measured with identified particles in $p$ -Pb/ $d$ -Au collisions have shown similar mass-splitting of $v_{2}^{hadron}$ indicating towards the presence of collective dynamics in small collision systems. Arguably, the small size in the overlap geometry of such colliding systems may not be suitable for hydrodynamical treatment that demands an early thermalization. Studies based on a multiphase transport model (AMPT) suggest that elliptic or triangular anisotropy is primarily due to the escape mechanism of partons rather than hydro-like collectivity and mass ordering of $v_{2}^{hadron}$ can be generated from coalescence dynamics as implemented in string melting version of AMPT even when parton azimuthal directions are randomized. In this work, studies have been performed on $p$ -Pb collisions at $\sqrt{s_{N N}} = 5.02$ TeV using AMPT model which has been found to explain the elliptic and triangular flow in such a system where the escape mechanism is the dominant source of flow generation. We report that the mass splitting of $v_{2}^{hadron}$ can originate independently both at the partonic and hadronic level in the string melting version of the AMPT model.