Speaker
Description
The data from RHIC Beam Energy Scan phase I (BES-I) have shown interesting results below $\sqrt{s_{NN}}<$ 19.6 GeV in identified hadron anisotropy ($v_1$, $v_2$, $v_3$), kaon over pion ratios, and net-proton higher moments. These interesting features continue to the lowest energy, $\sqrt{s_{NN}}$ = 7.7 GeV, and motivate the investigation to even lower energy collisions. The STAR fixed-target program extends the energy reach from $\sqrt{s_{NN}}$ =7.7 GeV to $\sqrt{s_{NN}}$ = 3.0 GeV, corresponding to baryon chemical potential 420 MeV to about 700 MeV range. The comparison of the asymmetric system (Al+Au) and symmetric system (Au+Au) at almost equal number of participating nucleons from most central to mid-central collisions provides useful information on nucleon stopping, which is key to understanding the baryon chemical potential.
We present results from Al (beam)+Au (target) collisions at $\sqrt{s_{NN}}$ = 4.9 GeV and Au+Au collisions at $\sqrt{s_{NN}}$ = 4.5 GeV from the STAR fixed-target program. We will report transverse mass spectra, rapidity density distributions, particle ratios, centrality dependence and directed flow of protons, $\pi^{\pm}$, $K_{s}$ and $\Lambda$, elliptic flow of protons, $\pi^{\pm}$ and K, and HBT homogeneity lengths of pions. Pion and proton elliptic flow show mass ordering. Number of constituent quark scaling tests will be presented. For the asymmetric Al+Au system, the peak of the rapidity density distributions is shifted from the nucleon-nucleon center-of-mass rapidity. The magnitude of this shift varies with centrality and is a measure of the nucleon stopping. These newly measured data will be compared with previously published results from the AGS and SPS. The implications of the results on future STAR fixed-target physics runs will be discussed.
| Content type | Experiment |
|---|---|
| Collaboration | STAR |
| Centralised submission by Collaboration | Presenter name already specified |
