We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 ≤
m≤ 2.0 GeV/c
2 is enhanced by a ...factor of 3.5 ± 0.4 (stat) ± 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV/c
2. For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lowest observed
p
⊥.
Statistical hadronization of charm: from FAIR to the LHC Andronic, A; Braun-Munzinger, P; Redlich, K ...
Journal of physics. G, Nuclear and particle physics,
10/2008, Letnik:
35, Številka:
10
Journal Article, Conference Proceeding
The production of the K⁎(892) strange resonance in Pb+Pb collisions at sNN=2.76 TeV LHC energy is analyzed within the integrated hydrokinetic model (iHKM) at different equations of state of ...superdense matter. The similar analysis is done also for the RHIC top energy sNN=200 GeV for comparison purposes. A modification of experimental K⁎(892)-identification is studied for different centralities in view of possible re-scattering of the decay products at the afterburner stage of the fireball evolution. We see quite intensive rescattering of the decay products as well as recombination processes for K⁎(892). In addition, the production of the much longer-long-lived ϕ(1020) resonance with hidden strange quark content is investigated.
An improved statistical model with excluded volume corrections and resonance decays is introduced and applied to the complete presently available set of particle ratios as measured by the various ...experiments at the SPS in Pb+Pb collisions. The results imply that a high degree of hadrochemical equilibration is reached at chemical freeze-out in Pb+Pb collisions.
In nucleus-nucleus collisions at ultra-relativistic energies matter is formed with initial energy density significantly exceeding the critical energy density for the transition from hadronic to ...partonic matter. We will review the experimental evidence for this new form of matter - the Quark-Gluon Plasma - from recent experiments at the SPS and RHIC with emphasis on collective behavior, thermalization, and its opacity for fast partons. We will further show that one can determine from the data a fundamental QCD parameter, the critical temperature for the QCD phase transition.
Recently it was conjectured that the strongly attractive antikaon–nucleon potential can result in the formation of antikaon nuclear bound states. We discuss the formation of such states as possible ...residues in heavy ion collisions. In this context, we calculate the excitation functions of single- and double-
K
− clusters in terms of the statistical thermal model. We show that, if such objects indeed exist, then, in heavy ion collisions, the single-
K
− clusters are most abundantly produced at present SIS energies, while the double-
K
− clusters show a pronounced maximum yield in the energy domain of the future accelerator at GSI. This is a direct consequence of: (i) the baryonic dominance in low energy heavy ion collisions and the large baryonic content of the antikaonic bound states; (ii) the strong energy dependence of strangeness production at low energies. The production yields of double-strange clusters is compared with that of double strange baryons. It is shown that at SIS energy there is a linear scaling relation of the
Ξ
−/
K
+ with
K
+/
p yields ratio.
Hadron production in relativistic nuclear collisions is well described in the framework of the Statistical Hadronization Model (SHM). We investigate the influence on SHM predictions of hadron mass ...spectra for light-flavor baryons and mesons modified by the addition of about 500 new states as predicted by lattice QCD and a relativistic quark model. The deterioration of the resulting thermodynamic fit quality obtained for Pb–Pb collision data at sNN=2.76 TeV suggests that the additional states are not suited to be naively used since also interactions among the states as well as non-resonant contributions need to be considered in the SHM approach. Incorporating these effects via the pion nucleon interaction determined from measured phase shifts leads again to excellent reproduction of the experimental data. This is a strong indication that at least the additional nucleon excited states cannot be understood and used as independent resonances.
We consider the charmonium production in the thermalized hadronic medium created in ultrarelativistic heavy ion collisions at LHC energy. The calculations for secondary \(J/\psi\) and ...\(\psi^{\prime}\) production by \(D\bar D\) annihilation are performed within a kinetic model taking into account the space-time evolution of a longitudinally and transversely expanding medium. We show that secondary charmonium production appears almost entirely during the mixed phase, and that it is very sensitive to the charmonium dissociation cross section with co-moving hadrons. Within the most likely scenario for the dissociation cross section of the \(J/\psi\) mesons their regeneration in the hadronic medium will be negligible. The secondary production of \(\psi^{\prime}\) mesons however, due to their large cross section above the threshold, can substantially exceed the primary yield.
Particle production in high-energy collisions is often addressed within the framework of the thermal (statistical) model. We present a method to calculate the canonical partition function for the ...hadron resonance gas with exact conservation of the baryon number, strangeness, electric charge, charmness and bottomness. We derive an analytical expression for the partition function which is represented as series of Bessel functions. Our results can be used directly to analyze particle production yields in elementary and in heavy ion collisions. We also quantify the importance of quantum statistics in the calculations of the light particle multiplicities in the canonical thermal model of the hadron resonance gas.
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