Charm quarks are more hydrodynamic than light quarks in final-state elliptic flow

Li, Hanlin (Hubei Province Key Laboratory of Systems Science in Metallurgical Process, Wuhan University of Science and Technology, Wuhan 430081, China) ; Lin, Zi-Wei (Key Laboratory of Quarks and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079, China) (Department of Physics, East Carolina University, Greenville, North Carolina 27858, USA) ; Wang, Fuqiang (School of Science, Huzhou University, Huzhou, Zhejiang 313000, China) (Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA)

17 April 2019

Abstract: We study the charm quark elliptic flow $\left({v}_{2}\right)$ in heavy ion as well as small system collisions by tracking the evolution history of quarks of different flavors within a multiphase transport model. The charm quark ${v}_{2}$ is studied as a function of the number of collisions the charm quark suffers with other quarks and then compared to the ${v}_{2}$ of lighter quarks. We find that the common escape mechanism is at work for both the charm and light quark ${v}_{2}$. However, contrary to the naive expectation, the hydrodynamics-type flow is found to contribute more to the final state charm ${v}_{2}$ than the light quark ${v}_{2}$. This could be explained by the smaller average deflection angle the heavier charm quark undergoes in each collision, so that heavy quarks need more scatterings to accumulate a significant ${v}_{2}$, while lighter quarks can more easily change directions with scatterings with their ${v}_{2}$ coming more from the escape mechanism. Our finding thus suggests that the charm ${v}_{2}$ is a better probe for studying the hydrodynamic properties of the quark-gluon plasma.

Published in: Physical Review C 99 (2019)
DOI: 10.1103/PhysRevC.99.044911
arXiv: 1804.02681

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