Strange Baryon Resonance Production in $\sqrt{s_{NN}}=200\mathrm{GeV}$ $p+p$ and $\mathrm{Au}+\mathrm{Au}$ Collisions

We report the measurements of $\Sigma (1385)$ and $\Lambda (1520)$ production in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ from the STAR Collaboration. The yields and the $p_T$ spectra are presented and discussed in terms of chemical and thermal freeze-out conditions and compared to model predictions. Thermal and microscopic models do not adequately describe the yields of all the resonances produced in central $\mathrm{Au}+\mathrm{Au}$ collisions. Our results indicate that there may be a time span between chemical and thermal freeze-out during which elastic hadronic interactions occur.

Figure 1

Invariant mass distributions of ${\Sigma }^{*}$ and ${\Lambda }^{*}$ in $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ before (inset) and after mixed-event background subtraction.

Figure 2

The transverse mass spectra for ${\Sigma }^{*}$ and ${\Lambda }^{*}$ in $p+p$ and in central $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. Statistical and systematical errors are included.

Figure 3

Resonance to stable particle ratios for $p+p$ and $\mathrm{Au}+\mathrm{Au}$ collisions. The ratios are normalized to unity in $p+p$ and compared to thermal and UrQMD model predictions for central $\mathrm{Au}+\mathrm{Au}$ [8, 12]. Statistical and systematic uncertainties are included in the error bars.