9 research outputs found
Statistical hadronization of charmed quarks at SPS and RHIC
Production of open and hidden charm hadrons in heavy ion collisions is
considered within the statistical coalescence model. The charmed
quark-antiquark pairs are assumed to be created at the initial stage of the
reaction in hard parton collisions. The number of these pairs is conserved
during the evolution of the system. At the hadronization stage, the charmed
(anti)quarks are distributed among open and hidden charm hadrons in accordance
with the laws of statistical mechanics.
The model is in agreement with the experimental data on J/psi to Drell-Yan
ratio in Pb+Pb collisions at SPS. This agreement can be reached only if a
rather strong enhancement of the open charm production in central Pb+Pb
collisions is assumed. A possible mechanism of the charm enhancement is
discussed.
At the top RHIC energy, the model predicts an increase of J/psi to Drell-Yan
ratio in more central nucleus-nucleus collisions with respect to less central
ones.Comment: Presented at 16th International Conference "Quark Matter", Nantes
(France), July 18-24, 2002; 4 pages, LaTeX, 2 PS-figure
Heavy Flavor Enhancement as a Signal of Color Deconfinement
We argue that the color deconfinement in heavy ion collisions may lead to
enhanced production of hadrons with open heavy flavor (charm or bottom). We
estimate the upper bound of this enhancement.Comment: 7 pages, LaTeX, 3 PS-figure
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.Comment: 7 pages, Late
production in PHENIX
Heavy quarkonia production is expected to be sensitive to the formation of a
quark gluon plasma (QGP). The PHENIX experiment has measured
production at ~200 GeV in Au+Au and Cu+Cu collisions, as well
as in reference p+p and d+Au runs. 's were measured both at mid
() and forward () rapidity. In this letter, we present
the A+A preliminary results and compare them to normal cold nuclear matter
expectations derived from PHENIX d+Au and p+p measurements as well as to
theoretical models including various effects (color screening, recombination,
sequential melting...).Comment: 5 pages, 7 figures. To appear in the proceedings of Hot Quarks 2006:
Workshop for Young Scientists on the Physics of Ultrarelativistic
Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May 200
Open charm and charmonium production at relativistic energies
We calculate open charm and charmonium production in reactions at
= 200 GeV within the hadron-string dynamics (HSD) transport approach
employing open charm cross sections from and reactions that are
fitted to results from PYTHIA and scaled in magnitude to the available
experimental data. Charmonium dissociation with nucleons and formed mesons to
open charm ( pairs) is included dynamically. The 'comover'
dissociation cross sections are described by a simple phase-space model
including a single free parameter, i.e. an interaction strength , that
is fitted to the suppression data for collisions at SPS
energies. As a novel feature we implement the backward channels for charmonium
reproduction by channels employing detailed balance. From our
dynamical calculations we find that the charmonium recreation is comparable to
the dissociation by 'comoving' mesons. This leads to the final result that the
total suppression at = 200 GeV as a function of centrality
is slightly less than the suppression seen at SPS energies by the NA50
Collaboration, where the 'comover' dissociation is substantial and the backward
channels play no role. Furthermore, even in case that all directly produced
mesons dissociate immediately (or are not formed as a mesonic state),
a sizeable amount of charmonia is found asymptotically due to the + meson channels in central collisions of at =
200 GeV which, however, is lower than the yield expected from binary
scaling of collisions.Comment: 42 pages, including 14 eps figures, discussions extended and
references added, to be published in Phys. Rev.
Charmonium from Statistical Hadronization of Heavy Quarks -- a Probe for Deconfinement in the Quark-Gluon Plasma
We review the statistical hadronization picture for charmonium production in
ultra-relativistic nuclear collisions. Our starting point is a brief reminder
of the status of the thermal model description of hadron production at high
energy. Within this framework an excellent account is achieved of all data for
hadrons built of (u,d,s) valence quarks using temperature, baryo-chemical
potential and volume as thermal parameters. The large charm quark mass brings
in a new (non-thermal) scale which is explicitely taken into account by fixing
the total number of charm quarks produced in the collision. Emphasis is placed
on the description of the physical basis for the resulting statistical
hadronization model. We discuss the evidence for statistical hadronization of
charmonia by analysis of recent data from the SPS and RHIC accelerators.
Furthermore we discuss an extension of this model towards lower beam energies
and develop arguments about the prospects to observe medium modifications of
open and hidden charm hadrons. With the imminent start of the LHC accelerator
at CERN, exciting prospects for charmonium production studies at the very high
energy frontier come into reach. We present arguments that, at such energies,
charmonium production becomes a fingerprint of deconfinement: even if no
charmonia survive in the quark-gluon plasma, statistical hadronization at the
QCD phase boundary of the many tens of charm quarks expected in a single
central Pb-Pb collision could lead to an enhanced, rather than suppressed
production probability when compared to results for nucleon-nucleon reactions
scaled by the number of hard collisions in the Pb-Pb system.Comment: review article, 27 pages, Landoldt review volume "Relativistic Heavy
Ion Physics", Reinhard Stock, edito
Charmonium dissociation and recombination at RHIC and LHC
Charmonium production at heavy-ion colliders is considered within the
comovers interaction model. The formalism is extended by including possible
secondary J/psi production through recombination and an estimate of
recombination effects is made with no free parameters involved. The comovers
interaction model also includes a comprehensive treatment of initial-state
nuclear effects, which are discussed in the context of such high energies. With
these tools, the model properly describes the centrality and the rapidity
dependence of experimental data at RHIC energy, = 200 GeV, for both
Au+Au and Cu+Cu collisions. Predictions for LHC, = 5.5 TeV, are
presented and the assumptions and extrapolations involved are discussed.Comment: 16 pages, 5 figure