Energy and system size dependence of ϕmeson production in Cu+Cu and Au+Au collisions

Abstract

We study the beam-energy and system-size dependence of φ meson production (using the hadronic decay mode φ → K + K − ) by comparing the new results from Cu+Cu collisions and previously reported Au+Au collisions at √ s NN = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from midrapidity (|y| <0.5) for 0.4 < p T < 5 GeV/c. At a given beam energy, the transverse momentum distributions for φ mesons are observed to be similar in yield and shape for Cu+Cu and Au+Au colliding systems with similar average numbers of participating nucleons. The φ meson yields in nucleus-nucleus collisions, normalised by the average number of participating nucleons, are found to be enhanced relative to those from p+p collisions with a different trend compared to strange baryons. The enhancement for φ mesons is observed to be higher at √ s NN = 200 GeV compared to 62.4 GeV. These observations for the produced φ(ss) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.

Centrality dependence of strangeness production in heavy-ion collisions as a geometrical effect of core–corona superposition

“…In fact, this means that the SCV would only reach its saturation value (the one sufficient for the system to be essentially grand-canonical) at RHIC precisely in central collisions, where γ S ≃ 1. Therefore, we think that canonical suppression is quite an unnatural explanation of the data, as pointed out by many [12,13,18,19].…”

K− AND $\overline p$ SPECTRA FOR Au+Au COLLISIONS AT $\sqrt s \, = \,200\,{\rm GeV}$ FROM STAR, PHENIX AND BRAHMS IN COMPARISON TO CORE-CORONA MODEL PREDICTIONS

“…The results are presented in [5]. The STAR [7] and PHENIX [9] collaborations found other and mutually different values of N part for the same centrality bins.…”

Energy scan by ϕ mesons and threshold energy for the confinement–deconfinement phase transition

“…NA49 and STAR collaboration have tabulated φ multiplicity and mean p T in Pb+Pb and Au+Au/Cu+Cu collisions in the energy range √ s= 6.3-200 GeV [17][18][19][20]. In Fig.…”

“…To conclude, we have argued that the ratio of φ mesons multiplicity over cube of the mean p T corresponds to the degeneracy of the medium produced in relativistic heavy ion collisions and can signal the confinementdeconfinement phase transition. The ratio constructed from the existing data [17][18][19][20] in the energy range √ s=6.3-200 GeV, even though have large error bars, do show rapid rise from low SPS energy to high RHIC energy. Using a result of hydrodynamical analysis of φ mesons p T spectra [25], that the average initial temperature depend logarithmically on the collision energy, the collision energy dependence of the ratio is converted in to temperature dependence.…”