Recent STAR heavy-ion results

The recent STAR heavy-ion results obtained in the first phase of the RHIC Beam Energy Scan program are presented. The measurements of particle spectra have been performed over a wide range of collision energy √ sNN=7.7-200 GeV, centrality and transverse momentum of produced particles. The fixed target mode in heavy-ion collisions at the STAR experiment also extends considerably the range of search for the new physics. Heavy quarks provide an exceptional probe in understanding properties of the hot and dense medium created in such collisions. The Heavy Flavor Tracker (HFT) and Muon Telescope Detector (MTD) upgrades at the STAR experiment at RHIC significantly improved the experimental capabilities of TPC, ToF and EMC detectors in measuring both open and hidden heavy flavor hadrons in heavy-ion collisions.

Study the Structure of Nuclear Matter with QCD Degrees of Freedom Phase structure of QCD matter is experimentally studied at SPS, RHIC and LHC Dense, strongly-coupled matter and an almost perfect liquid with partonic collectivity has been created in HIC at RHIC. STAR, PHENIX, PHOBOS, BRAHMS -White papers -Nucl. Phys. A757 (2005) Experimental results from the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) support the hypothesis that a stronglycoupled nuclear medium with partonic degrees of freedom, namely the Quark-Gluon Plasma (QGP), is created in heavy-ion collisions at high energy.
"The Hot QCD White Paper: Exploring the Phases of QCD at RHIC and the LHC" -arXiv: 1502

Momentum-Space Anisotropy
 v 1 (y) sensitive to baryon transport, space momentum correlations and QGP formation.
 v 2 provides the possibility to gain information about the degree of thermalization of the hot, dense medium.  The breaking of v 2 number of quark scaling will indicate a transition from partonic to hadronic degrees of freedom.

Fragmentation dimension
Nucleus fractal dimension  δ decreases with energy for √s NN ≤ 20 GeV  δ is independent of energy for √s NN ≥ 20 GeV  ε AA increases with energy  c is independent of energy Parameters δ A , ε AA , c are determined from the requirement of scaling behavior of Ψ as a function of self-similarity parameter z c "Specific heat" Search for discontinuity and correlations of the model parameters. The values of net-Kaon's and net-Charge's κσ 2 and Sσ/Skellam are consistent with Poisson distributions within errors.
Search for probe non-gaussian fluctuations near the Critical Point BES I results for Au+Au & 7.7,11.5,14.5,19.6,27,39,62.4,200 GeV Need more precise measurement below 20 GeV with finer steps in μ B and increased rapidity acceptance A reduction in the partonic energy loss.
Non-monotonic variation with respect to μ B . Sensitivity to possible firstorder phase transition effects.
To clarify whether the trend follows a monotonic or nonmonotonic variation with a minimum.
A difference between the v 2 of baryons and mesons at intermediate p T is the key to the experimental observation of NCQ scaling and partonic collectivity at top RHIC energy.
The difference in v 2 between baryons and antibaryons are consistent with the finding that hadronic interactions dominate at lower beam energies..
The difference of dynamical charge correlations between same-sign and opposite-sign charges. One of the possible explanations is the Chiral Magnetic Effect. Fixed target program at STAR probing QCD phase diagram with identified particles over a range √s NN = 3.0 to 7.7 GeV The Fixed-Target Program will extend the reach of the RHIC BES to higher μ B and lower T.

Goals:
 Search for evidence of the first entrance into the mixed phase.  Conclusions  Some of STAR results from RHIC Beam Energy Scan-I were reviewed.  The wide range of collision energy (√s NN =7-200 GeV), centrality, various probes (π,p,K,J/ψ,e,μ,Λ,Ξ,Ω, d,..) allows us to scan the phase diagram of nuclear matter over a wide range of T and μ B .  The obtained data are basis for verification of different theoretical models, transition scenarios and properties of nuclear matter (the hydro of ideal liquid, NCQ scaling, jet quenching, the spinning QGP etc.)  The collider and fixed target modes with new detector systems (HFT, MTD, iTPC, EPD, eTOF) significantly improve the capabilities of STAR for BES II to detect key features of QCD phase diagram.