Elliptic flow of hadrons in equal-velocity quark combination mechanism in relativistic heavy-ion collisions

Abstract

Abstract We apply a quark combination model with equal-velocity combination (EVC) approximation to study the elliptic flow ( $$v_{2}$$ v 2 ) of hadrons in heavy-ion collisions in a wide collision energy range ( $$\sqrt{s_{NN}}=$$ s NN = 27–5020 GeV). Utilizing the simple relationship between $$v_{2}$$ v 2 of hadrons and those of quarks under EVC, we find that $$v_{2}$$ v 2 of up/down quarks obtained by experimental data of proton is consistent with that obtained by data of $$\varLambda $$ Λ and $$\varXi $$ Ξ . $$v_{2}$$ v 2 of strange quarks obtained by data of $$\varOmega $$ Ω is consistent with that obtained by data of $$\varLambda $$ Λ and $$\varXi $$ Ξ , and at RHIC energies it is also consistent with that obtained by data of $$\phi $$ ϕ . This means that $$v_{2}$$ v 2 of these hadrons have a common quark-level source. Using data of $$D^0$$ D 0 , we obtain $$v_{2}$$ v 2 of charm quarks with $$p_T\lesssim 6$$ p T ≲ 6 GeV/c. We find that under EVC charm quark dominates $$v_{2}$$ v 2 of D mesons at low $$p_{T}$$ p T but light-flavor quarks significantly contribute to $$v_{2}$$ v 2 of D mesons in the range $$3\lesssim p_{T}\lesssim 8$$ 3 ≲ p T ≲ 8 GeV/c. We predict $$v_{2}$$ v 2 of charmed baryons $$\varLambda _{c}^{+}$$ Λ c + and $$\varXi _{c}^{0}$$ Ξ c 0 which show a significant enhancement at intermediate $$p_{T}$$ p T due to the double contribution of light-flavor quarks. The properties of the obtained quark $$v_{2}$$ v 2 under EVC are studied and a regularity for $$v_{2}$$ v 2 of quarks as the function of $$p_{T}/m$$ p T / m is found.