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The transverse mass spectra of J/psi and psi' mesons and Omega hyperons produced in central Au+Au collisions at RHIC energies are discussed within a statistical model used successfully for the interpretation of the SPS results. The comparison of the presented model with the future RHIC data should serve as a further crucial test of the hypothesis of statistical production of charmonia at hadronization. Finally, in case of validity, the approach should allow to estimate the mean transverse flow velocity at the quark gluon plasma hadronization.
The transverse mass spectra of J/ψ and ψ′ mesons and Ω hyperons produced in central Au+Au collisions at RHIC energies are discussed within a statistical model used successfully for the interpretation of the SPS results. The comparison of the presented model with the future RHIC data should serve as a further crucial test of the hypothesis of statistical production of charmonia at hadronization. Finally, in case of validity, the approach should allow to estimate the mean transverse flow velocity at the quark–gluon plasma hadronization.
The transverse mass spectra of Omega, J/psi and psi' in Pb+Pb collisions at 158 AGeV are studied within a hydrodynamical model of the quark gluon plasma expansion and hadronization. The model reproduces the existing data with the common hadronization parameters: temperature T=T_H = 170 MeV and average collective transverse velocity v_T = 0.2.
The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons – the QvdW-HRG model – is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for χBQ11/χB2, effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of χB2, but it also leads to a worse description of χBQ11/χB2, as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.
Conventional cluster and virial expansions are generalized to momentum dependent interparticle potentials. The model with Lorentz contracted hard core potentials is considered, e.g. as hadron gas model. A Van der Waals-type model with a temperature dependent excluded volume is derived. Lorentz contraction effects at given temperature are stronger for light particles and make their effective excluded volume smaller than that of heavy ones.
Recent results on transverse mass spectra of J/psi and psi prime mesons in central Pb+Pb collisions at 158 AGeV are considered. It is shown that those results support a hypothesis of statistical production of charmonia at hadronization and suggest the early thermal freeze-out of J/psi and psi prime mesons. Based on this approach the collective transverse velocity of hadronizing quark gluon plasma is estimated to be <v^H_T> \approx 0.2. Predictions for transverse mass spectra of hidden and open charm mesons at SPS and RHIC are discussed.
Transverse activity of kaons and the deconfinement phase transition in nucleus-nucleus collisions
(2003)
We found that the experimental results on transverse mass spectra of kaons produced in central Pb+Pb (Au+Au) interactions show an anomalous dependence on the collision energy. The inverse slopes of the spectra increase with energy in the low (AGS) and high (RHIC) energy domains, whereas they are constant in the intermediate (SPS) energy range. We argue that this anomaly is probably caused by a modification of the equation of state in the transition region between confined and deconfined matter. This observation may be considered as a new signal, in addition to the previously reported anomalies in the pion and strangeness production, of the onset of deconfinement located in the low SPS energy domain.
Transverse activity of kaons and deconfinement phase transition in nucleus–nucleus collisions
(2003)
We found that the experimental results on transverse mass spectrum of kaons produced in central Pb+Pb (Au+Au) collisions show an anomalous dependence on the colliding energy. The inverse slope of the spectrum increases with the energy in the low (AGS) and high (RHIC) energy domains, whereas it remains constant in the intermediate (SPS) energy range. We argue that this anomaly is probably caused by the modification of the equation of state in the transition region between confined and deconfined matter. This observation may be considered as a new signal, in addition to the previously reported anomalies in the pion and strangeness production, of the onset of deconfinement located in the low SPS energy domain.
We propose to use the hadron number fluctuations in the limited momentum regions to study the evolution of initial flows in high energy nuclear collisions. In this method by a proper preparation of a collision sample the projectile and target initial flows are marked in fluctuations in the number of colliding nucleons. We discuss three limiting cases of the evolution of flows, transparency, mixing and reflection, and present for them quantitative predictions obtained within several models. Finally, we apply the method to the NA49 results on fluctuations of the negatively charged hadron multiplicity in Pb+Pb interactions at 158A GeV and conclude that the data favor a hydrodynamical model with a significant degree of mixing of the initial flows at the early stage of collisions.
We propose to use the hadron number fluctuations in the limited momentum regions to study the evolution of initial flows in high energy nuclear collisions. In this method by a proper preparation of a collision sample the projectile and target initial flows are marked in fluctuations in the number of colliding nucleons. We discuss three limiting cases of the evolution of flows, transparency, mixing and reflection, and present for them quantitative predictions obtained within several models. Finally, we apply the method to the NA49 results on fluctuations of the negatively charged hadron multiplicity in Pb+Pb interactions at 158A GeV and conclude that the data favor a hydrodynamical model with a significant degree of mixing of the initial flows at the early stage of collisions.