437 research outputs found
Statistical J/psi production and open charm enhancement in Pb+Pb collisions at CERN SPS
Production of open and hidden charm hadrons in heavy ion collisions is
considered within the statistical coalescence model. Charmed quarks and
antiquarks are assumed to be created at the initial stage of the reaction and
their number is conserved during the evolution of the system. They are
distributed among open and hidden charm hadrons at the hadronization stage in
accordance with laws of statistical mechanics. The model is in excellent
agreement with the experimental data on J/psi production in lead-lead
collisions at CERN SPS and predicts strong enhancement of the open charm
multiplicity over the standard extrapolation from nucleon-nucleon to
nucleus-nucleus collisions. A possible mechanism of the charm enhancement is
proposed.Comment: Presented at 6th International Conference on Strange Quarks in
Matter, Frankfurt am Main, 2001. 4 pages, LaTeX, 1 PS-figur
Phase transition in hot pion matter
The equation of state for the pion gas is analyzed within the third virial approximation. The second virial coeffcient is found from the pi pi -scattering data, while the third one is considered as a free parameter. The proposed model leads to a first-order phase transition from the pion gas to a more dense phase at the temperature Tpt < 136 MeV. Due to relatively low temperature this phase transition cannot be related to the deconfinement. This suggests that a new phase of hadron matter hot pion liquid may exist
Statistical coalescence model with exact charm conservation
The statistical coalescence model for the production of open and hidden charm is considered within the canonical ensemble formulation. The data for the J/psi multiplicity in Pb+Pb collisions at 158 A·GeV are used for the model prediction of the open charm yield which has not yet been measured in these reactions
J / psi suppression and enhancement in Au + Au collisions at the BNL RHIC
We consider the production of the J/psi mesons in heavy ion collisions at RHIC energies in the statistical coalescence model with an exact (canonical ensemble) charm conservation. The cc quark pairs are assumed to be created in the primary hard parton collisions, but the formation of the open and hidden charm particles takes place at the hadronization stage and follows the prescription of statistical mechanics. The dependence of the J/psi production on both the number of nucleon participants and the collision energy is studied. The model predicts the J/psi suppression for low energies, whereas at the highest RHIC energy the model reveals the J/psi enhancement
J/psi Suppression and Enhancement in Au+Au Collisions at the BNL RHIC
We consider the production of the J/psi mesons in heavy ion collisions at
RHIC energies in the statistical coalescence model with an exact (canonical
ensemble) charm conservation. The c\bar{c} quark pairs are assumed to be
created in the primary hard parton collisions, but the formation of the open
and hidden charm particles takes place at the hadronization stage and follows
the prescription of statistical mechanics. The dependence of the J/psi
production on both the number of nucleon participants and the collision energy
is studied. The model predicts the J/psi suppression for low energies, whereas
at the highest RHIC energy the model reveals the J/psi enhancement.Comment: 14 pages, REVTeX, 3 PS-figure
The high E(T) drop of J / psi to Drell-Yan ratio from the statistical c anti-c coalescence model
The dependence of the J/psi yield on the transverse energy ET in heavy ion collisions is considered within the statistical c¯c coalescence model. The model fits the NA50 data for Pb+Pb collisions at the CERN SPS even in the high-ET region (ET >< 100 GeV). Here ET -fluctuations and ET -losses in the dimuon event sample naturally create the celebrated drop in the J/psi to Drell-Yan ratio
Statistical Coalescence Model Analysis of J/psi Production in Pb+Pb Collisions at 158 A GeV
Production of J/\psi mesons in heavy ion collisions is considered within the
statistical coalescence model. The model is in agreement with the experimental
data of the NA50 Collaboration for Pb+Pb collisions at 158 A GeV in a wide
centrality range, including the so called ``anomalous'' suppression domain. The
model description of the J/psi data requires, however, strong enhancement of
the open charm production in central Pb+Pb collisions. This model prediction
may be checked in the future SPS runs.Comment: 13 pages, REVTeX, 2 PS-figure
Charm coalescence at relativistic energies
The J/psi yield at midrapidity at the top RHIC (relativistic heavy ion
collider) energy is calculated within the statistical coalescence model, which
assumes charmonium formation at the late stage of the reaction from the charm
quarks and antiquarks created earlier in hard parton collisions. The results
are compared to the new PHENIX data and to predictions of the standard models,
which assume formation of charmonia exclusively at the initial stage of the
reaction and their subsequent suppression. Two versions of the suppression
scenario are considered. One of them assumes gradual charmonium suppression by
comovers, while the other one supposes that the suppression sets in abruptly
due to quark-gluon plasma formation. Surprisingly, both versions give very
similar results. In contrast, the statistical coalescence model predicts a few
times larger yield in the most central collisions.Comment: 5 pages, RevTeX4, 1 PS-figure. V2: The final PHENIX data are analyze
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