High-pT results from the STAR experiment at RHIC

Abstract

High-p T measurements in relativistic heavy ion collisions provide a unique set of tools to investigate the early stages of the collision. In this paper we report the high-pT measurements of inclusive hadron spectra, azimuthal anisotropies and two particle correlations performed by the STAR detector for 200 GeV Au+Au, p+p and d+Au collisions at RHIC. The results suggest that the phenomena observed uniquely in central Au+Au collisions are due to strong final state interactions in the hot and dense medium created in such collisions.One of the main goals in the study of heavy ion collisions at relativistic energies is the understanding of the matter behavior at extreme temperature and densities conditions. QCD calculations predict that a phase transition from hadronic matter to a deconfined plasma of quarks and gluons may occur in such conditions [1]. Energetic partons propagating through the medium are expected to loose energy [2] and the magnitude of the energy loss is strongly dependent on the gluon density of the medium. Hard scattering of partons occurs early in the collision. In this case, partons emerging from such collisions probe the early phase of the evolution of the system and may provide important information about the characteristics of the hot and dense matter that is created. The hard scattering and subsequent fragmentation of these partons usually generates jets of correlated hadrons. In a clean, low multiplicity event it is possible to reconstruct the jet, making it possible directly to measure the parton characteristics. In a high multiplicity event, as the one originated from central Au+Au collisions, the soft background makes the jet reconstruction impossible. In this case, indirect studies of parton hard scattering, such as high-p T single hadron spectra and high-p T azimuthal correlations, may reveal important information about the propagating parton. Parton energy loss in the medium softens the fragmentation of jets, leading to a suppression of the hightransverse momentum hadrons [3]. Several high-p T results from RHIC have already been reported [4][5][6][7][8][9][10][11] and are consistent with large partonic energy loss in high energy density matter. This paper reports the results from the data taking with the STAR detector [12] for the Au+Au, p+p and d+Au systems at GeV. Details of the analysis can be found in Ref.[4,7-11].The invariant yields for charged hadrons (h + + h − )/2 at mid-rapidity are found in Fig. 1. Each curve represents a different centrality selection with different scale factors for clarity purposes. Event centrality selection is made using the uncorrected number of primary tracks with number of fit points larger than 10 in the pseudorapidity range of |η| < 0.5 . The bottom curve is the yield obtained for p+p collisions. Spectra are corrected for tracking efficiency, background and momentum resolution [9]. The errors indicated include both statistical and systematic uncertainties and are visible only in the high momentum region.In order to understand any modification in ...

A q-parameter bound for particle spectra based on black hole thermodynamics with Rényi entropy

“…In earlier works we have fitted several hadron spectra observed at RHIC [12,13,14,15,16,17,18] by assuming a blast wave picture and quark recombination [19,20]. These fits agreed with a common Tsallis parameter of q ≈ 1.2 for the quark matter quite remarkably.…”

“…By analyzing the thermodynamics given by the equations in (18), one realizes that it is surprisingly similar to the one of a black hole in AdS space [27]. Consequently we now obtain simultaneously the Rényi-entropy based thermodynamics of the simple Schwarzschild black hole (discussed above) and the original Bekenstein-Hawking entropy based thermodynamics of a black hole in anti-de Sitter space.…”

Abstract composition rule for relativistic kinetic energy in the thermodynamical limit

“…-One of the theoretically challenging questions related to relativistic heavy-ion physics is how to establish the existence of a thermal or near thermal state of (quark) matter during high-energy collisions. Besides studies of the hadronic flavor composition [1][2][3][4][5], the shape and the steepness of transverse momentum spectra on different particles presents experimental information on this question [6][7][8][9][10][11][12]. Since for high energies of the out-coming particles (pions, kaons, antiprotons, etc.)…”

Non-Extensive Black Hole Thermodynamics Estimate for Power-Law Particle Spectra

“…In an earlier work we have fitted several hadron spectra observed at RHIC [6][7][8][9][10][11][12] by assuming a blast wave picture and quark recombination [13]. These fits agreed with a common Tsallis parameter of q ≈ 1.2 for the quark matter quite remarkably.…”