Testing the collectivity in large and small colliding systems with test particles

Abstract

We propose a test-particle method to probe the transport dynamics of establishment and development of collective flow in large and small systems of heavy-ion collisions. We place test particles as passengers into the partonic medium created by Au+Au mid-central collisions atGeV and p+Pb central collisions at √ sNN = 5.02 TeV, using a multiphase transport model. With the help of test particles in two extreme test cases, we demonstrate that parton collisions play an important role in establishing (or destroying) the collectivity in large and small colliding systems.The collectivity established by final state parton collisions is much stronger in large colliding systems compared to small colliding systems. The collectivity from initial state can persist or survive more easily in small colliding systems than in large colliding systems due to fewer parton collisions. Our study provides some new insights to understand the origin of collectivity in large and small colliding systems at RHIC and the LHC.