$\rho (770{)}^0$ and $f_0(980)$ Production in Au+Au and pp Collisions at $\sqrt{s_{NN}}$ = 200 GeV

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$f_0(980) \to \pi^+\pi^-$inheavy-ioncollisions\mathrm{.}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 ${\rho }^0\mathrm{/}{\pi }^{-}$ and the $f_0\mathrm{/}{\pi }^{-}$ ratios are compared to measurements in pp and e${}^{+}$e${}^{-}$ interactions at various energies.