Centrality dependence of $p_T$ spectra for identified hadrons in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV

The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV is systematically studied in a quark combination model. The ${\mathrm{p}}_{\mathrm{T}}$ spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p(\bar{p})$ and $\mathrm{\Lambda }(\bar{\mathrm{\Lambda }})$ in different centrality bins and the nuclear modification factors ($R_{CP}$) for these hadrons are calculated. The centrality dependence of the average collective transverse velocity $<\beta (r)>$ for the hot and dense quark matter is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu collision system. The centrality dependence of ${\mathrm{p}}_{\mathrm{T}}$ spectra and the $R_{CP}$ for ${\pi }^0$, $K_s^0$ and $\mathrm{\Lambda }$ in Cu+Cu collisions at $\sqrt{s_{NN}}=200$ GeV are well described. The results show that $<\beta ®>$isonlyafunctionofthenumberofparticipants$N_{part}$ and it is independent of the collision system.