Review of Recent Results From the Rhic Beam Energy Scan

Abstract

We review recent results from the RHIC beam energy scan (BES) program, aimed to study the Quantum Chromodynamics (QCD) phase diagram. The main goals are to search for the possible phase boundary, softening of equation of state or first order phase transition, and possible critical point. Phase-I of the BES program has recently concluded with data collection for Au+Au collisions at center-of-mass energies ( √ s NN ) of 7.7, 11.5, 19.6, 27 and 39 GeV. Several interesting results are observed for these lower energies where the net-baryon density is high at the mid-rapidity. These results indicate that the matter formed at lower energies (7.7 and 11.5 GeV) is hadron dominated and might not have undergone a phase transition. In addition, a centrality dependence of freeze-out parameters is observed for the first time at lower energies, slope of directed flow for (net)-protons measured versus rapidity shows an interesting behavior at lower energies, and higher moments of net-proton show deviation from Skellam expectations at lower energies. An outlook for the future BES Phase-II program is presented and efforts for the detailed study of QCD phase diagram are discussed. Mod. Phys. Lett. A 2013.28. Downloaded from www.worldscientific.com by UNIVERSITY OF PITTSBURGH on 02/08/15. For personal use only. 1330033-2 Mod. Phys. Lett. A 2013.28. Downloaded from www.worldscientific.com by UNIVERSITY OF PITTSBURGH on 02/08/15. For personal use only. Review of Recent Results from the RHIC Beam Energy Scan 1330033-3 Mod. Phys. Lett. A 2013.28. Downloaded from www.worldscientific.com by UNIVERSITY OF PITTSBURGH on 02/08/15. For personal use only.

Inhomogeneous chiral condensates

“…(12) and (13), with L NJL replaced by L QM and the path integral performed over the meson fields as well. In this context we recall that in the bosonized NJL model one also has to integrate over the meson fields, as long as one does not resort to the mean-field approximation.…”

“…In particular, while great progress has been made in the past few years in characterizing strong-interaction matter at finite temperature thanks to the development of ab-initio lattice calculations [8] and to increasingly accurate data from heavy-ion collision experiments (see, e.g., [9]), the nature of QCD at finite densities (or baryon chemical potentials) is still poorly understood (see [10,11] for reviews on recent theoretical developments). On the experimental side, most heavy-ion data focuses on the high-temperature regime [9], and only recently the attention has started shifting to the finite-density region, particularly with the new beam energy scan runs at RHIC in Brookhaven [12] and the upcoming facilities FAIR in Darmstadt [13] and NICA in Dubna [14]. From a theoretical point of view, since lattice simulations at finite chemical potentials are plagued by the sign problem [15], in order to investigate the intermediate-density region it is necessary to employ other approaches.…”

Centrality and multiparticle production in ultrarelativistic nuclear collisions

“…These investigations have been continued to date by varying both the energy and the masses of colliding nuclei [25]. In particular, the Beam Energy Scan (BES) program was launched for the RHIC nuclear beam in Berkeley [26,27]. A more detailed analysis of special features of the phase diagram of strongly interacting matter and properties of QCD in the region of a significant baryon excess will become possible after the accumulation of high-statistics data in the future experiments CBM at the FAIR collider (Germany), which is under construction, and MPD at the NICA collider of the Joint Institute of Nuclear Research (JINR, Dubna) [28,29].…”

Cross-over versus first-order phase transition in holographic gravity–single-dilaton models of QCD thermodynamics

“…Parallel to the theoretical attempts, also special experimental searches are conducted, e.g. the beam energy scan at RHIC [12,13].…”