Elliptic flow of heavy-flavor decay electrons in Au plus Au collisions at vsNN=27 and 54.4 GeV at RHIC

作者：Abdulhamid, M. I.; Aboona, B. E.; Adam, J.; Adamczyk, L.; Adams, J. R.; Aggarwal, I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, D. M.; Aschenauer, E. C.; Aslam, S.; Atchison, J.; Bairathi, V.; Baker, W.; Cap, J. G. Ball; Barish, K.; Bellwied, R.; Bhagat, P.; Bhasin, A.; Bhatta, S.; Bielcik, J.; Bielcikova, J.; Brandenburg, J. D.; Butterworth, J.; Cai, X. Z.; Caines, H.; Sanchez, M. Calderon de la Barca; Cebra, D.; Ceska, J.; Chakaberia, I.; Chaloupka, P.; Chan, B. K.; Chang, Z.; Chatterjee, A.

来源：Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics , 2023, 844: 138071.

DOI：10.1016/j.physletb.2023.138071

• Heavy-flavor decay electron
• Elliptic flow
• Charm quark spatial diffusion coefficient

We report on new measurements of elliptic flow (v(2)) of electrons from heavy-flavor hadron decays at mid-rapidity (|y| < 0.8) in Au+Au collisions at vs(NN) = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons (eHF) in Au+Au collisions at vs(NN) = 54.4 GeV exhibit a non-zero v(2) in the transverse momentum (p(T)) region of p(T) < 2 GeV/c with the magnitude comparable to that at vs(NN) = 200 GeV. The measured e(HF) v(2) at 54.4 GeV is also consistent with the expectation of their parent charm hadron v(2) following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at vs(NN) = 54.4 GeV. The measured e(HF) v(2) in Au+Au collisions at vs(NN) = 27 GeV is consistent with zero within large uncertainties. The energy dependence of v(2) for different flavor particles (p, f, D-0/e(HF)) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.