Thermal analysis of production of resonances in relativistic heavy-ion collisions

Production of resonances is considered in the framework of the single-freeze-out model of ultrarelativistic heavy-ion collisions. The formalism involves the virial expansion, where the probability to form a resonance in a two-body channel is proportional to the derivative of the phase shift with respect to the invariant mass. The thermal model incorporates the longitudinal and the transverse flow, as well as kinematic cuts of the STAR experiment at RHIC. We find that the shape of the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ spectral line qualitatively reproduces the preliminary experimental data when the position of the $\ensuremath{\rho}$ peak is lowered. This confirms the need to include the medium effects in the description of the RHIC data. We also analyze the transverse-momentum spectra of $\ensuremath{\rho},$ ${K}^{*}{(892)}^{0},$ and ${f}_{0}(980),$ and find that the slopes agree with the observed values. Predictions are made for $\ensuremath{\eta},$ ${\ensuremath{\eta}}^{\ensuremath{'}},$ $\ensuremath{\omega},$ $\ensuremath{\varphi},$ $\ensuremath{\Lambda}(1520),$ and $\ensuremath{\Sigma}(1385).$