Abstract
We apply a quark combination model with equal-velocity combination (EVC) approximation to study the elliptic flow (v2) of hadrons in heavy-ion collisions in a wide collision energy range (sNN= 27–5020 GeV). Utilizing the simple relationship between v2 of hadrons and those of quarks under EVC, we find that v2 of up/down quarks obtained by experimental data of proton is consistent with that obtained by data of Λ and Ξ. v2 of strange quarks obtained by data of Ω is consistent with that obtained by data of Λ and Ξ, and at RHIC energies it is also consistent with that obtained by data of ϕ. This means that v2 of these hadrons have a common quark-level source. Using data of D0, we obtain v2 of charm quarks with pT≲6 GeV/c. We find that under EVC charm quark dominates v2 of D mesons at low pT but light-flavor quarks significantly contribute to v2 of D mesons in the range 3≲pT≲8 GeV/c. We predict v2 of charmed baryons Λc+ and Ξc0 which show a significant enhancement at intermediate pT due to the double contribution of light-flavor quarks. The properties of the obtained quark v2 under EVC are studied and a regularity for v2 of quarks as the function of pT/m is found.