Origin of the mass splitting of elliptic anisotropy in a multiphase transport model

Li, H. L. and He, L. and Lin, Z. W. and Molnár, Dénes and Wang, F. Q. (2016) Origin of the mass splitting of elliptic anisotropy in a multiphase transport model. PHYSICAL REVIEW C, 93 (5). ISSN 2469-9985

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Abstract

The mass splitting of elliptic anisotropy (v2) at low transverse momentum is considered as a hallmark of hydrodynamic collective flow. We investigate a multiphase transport (AMPT) model where the v2 is mainly generated by an anisotropic escape mechanism, not of the hydrodynamic flow nature, and where mass splitting is also observed. We demonstrate that the v2 mass splitting in AMPT is small right after hadronization (especially when resonance decays are included); the mass splitting mainly comes from hadronic rescatterings, even though their contribution to the overall charged hadron v2 is small. These findings are qualitatively the same as those from hybrid models that combine hydrodynamics with a hadron cascade. We further show that there is no qualitative difference between heavy ion collisions and small system collisions. Our results indicate that the v2 mass splitting is not a unique signature of hydrodynamic collective flow and thus cannot distinguish whether the elliptic flow is generated mainly from hydrodynamics or the anisotropic parton escape.

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