$\rho(770)^0$ and $f_{0}(980)$ Production in Au+Au and pp Collisions at $\sqrt{s_{NN}}$ = 200 GeV

Abstract

Preliminary results on $\rho(770)^0$ and $f_{0}(980)$ production at mid-rapidity using the mixed-event technique are presented. The $\rho^0$ and $f_0$ measurements via their hadronic decay channel in minimum bias pp and peripheral Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV were performed using the STAR detector at RHIC. This is the first direct measurement of $\rho^0(770) \to \pi^+\pi^-$ and $f_0(980) \to \pi^+\pi^-$ in heavy-ion collisions. The $\rho^0$ mass is transverse momentum dependent and significantly shifted in minimum bias pp and peripheral Au+Au interactions. The modifications of masses, widths and line shapes of short-lived resonances due to phase space and dynamical effects are discussed. The $\rho^0/\pi^-$ and the $f_0/\pi^-$ ratios are compared to measurements in pp and e$^{+}$e$^{-}$ interactions at various energies.