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

TL;DR

This paper investigates the origins of mass splitting in elliptic flow in p-Pb collisions at 5.02 TeV, demonstrating that both partonic and hadronic dynamics contribute to this phenomenon, challenging the exclusive role of hydrodynamics.

Contribution

It shows that mass splitting of $v_{2}^{hadron}$ can arise independently from partonic and hadronic stages within the AMPT model, highlighting multiple mechanisms behind flow development.

Findings

Mass splitting of $v_{2}^{hadron}$ can originate at both partonic and hadronic levels.

Escape mechanism is identified as the primary source of flow in small systems.

AMPT model reproduces flow phenomena without requiring hydrodynamic thermalization.

Abstract

The mass ordering of $v_{2}^{hadron}$ is regarded as one of the key signatures of collective behaviour in ultra relativistic 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 co-efficients 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, 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 multi phase transport model suggests that elliptic or triangular anisotropy is primarily due to 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 $\sqrt{s_{NN}}$ = 5.02 TeV using AMPT model which has been found to explain the elliptic and traingular flow in such a system where 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.