13-19 May 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

Recent Results from the STAR Fixed-Target Program

15 May 2018, 16:00
Sala Casinò, 1st Floor (Palazzo del Casinò)

Sala Casinò, 1st Floor

Palazzo del Casinò

Parallel Talk High baryon density and astrophysics High baryon density and astrophysics


Yang Wu (Kent State University)


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.

Centralised submission by Collaboration Presenter name already specified
Content type Experiment
Collaboration STAR

Primary author

Zhenyu Ye (University of Illinois at Chicago)

Presentation Materials