J∕ψproduction inAu-Aucollisions atsNN<

Abstract

First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/'s measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at ͱ s NN = 200 GeV is analyzed as a function of collision centrality. For this analysis we have studied 49.3ϫ 10 6 minimum bias Au-Au reactions. We present the J/ invariant yield dN/dy for peripheral and midcentral reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare these results with our J/ measurement from proton-proton reactions at the same energy. We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.

Initial, effective, and kinetic freeze-out temperatures from transverse momentum spectra in high-energy proton(deuteron)–nucleus and nucleus–nucleus collisions

“…Figure 1 presents the transverse momentum spectra, (1/2πp T )d 2 N/dp T dy, of (a)-(c) π + , K + , and p, as well as (b)-(d) π − , K − , andp produced in (a)-(b) 0-5% and (c)-(d) 60-92% Au-Au collisions at center-ofmass energy per nucleon pair √ s N N = 200 GeV. The squares, circles, and triangles represent respectively the experimental data of π + (π − ), K + (K − ), and p (p) measured by the PHENIX Collaboration in the pseudorapidity range |η| < 0.35 [20]. The solid and dotted curves are our results fitted by the first component in Eq.…”

“…In this paper, the transverse momentum spectra of positively and negatively charged pions (π + and π − ), positively and negatively charged kaons (K + and K − ), and protons (p) and antiprotons (p) produced in central and peripheral gold-gold (Au-Au) and deuterongold (d-Au) collisions at the Relativistic Heavy Ion Collider (RHIC) [20,21], as well as in central and peripheral lead-lead (Pb-Pb) and proton-lead (p-Pb) collisions at the Large Hadron Collider (LHC) [22,23,24] are fitted by the Hagedorn thermal model [25] and Boltzmann distribution [18] in terms of multi-component which is harmonious with a multisource thermal model used in our previous work [10]. The related temperatures which include the initial, effective, and kinetic freeze-out temperatures are then extracted from the fittings.…”

Chemical potentials of light hadrons and quarks from yield ratios of negative to positive particles in high energy pp collisions

“…Due to the infamous sign problem in LQCD, calculations for non-vanishing chemical potentials are very difficult [25][26][27][28]. By using the yield ratios of negative to positive particles [29][30][31] to obtain chemical potential is an effective and simple research method. We are interested in studying the chemical potentials of different types of particles, and their dependencies on transverse momentum and center-of-mass energy in pp collisions on the basis of yield ratios of negative to positive particles.…”

Prospects for Quarkonium Measurements in p–A and A–A Collisions at the LHC

“…In the charmonium sector, ALICE presented a clear sign of a low transverse momentum (p T ) J/ψ production component leading to a larger nuclear modification factor R AA [7,8,9,10,12], i.e., a weaker suppression compared to the results at RHIC by PHENIX [13] and STAR [14,15] for the p T integrated results and at low p T . This increase has been widely interpreted as a signature of late-stage J/ψ production either during the life-time of the deconfined medium produced in heavy-ion collisions proposed in Ref.…”