Le quarkonium : du Fermilab au SPS

École thématiqu

Production of Strange Clusters and Strange Matter in Nucleus-Nucleus Collisions at the AGS

Production probabilities for strange clusters and strange matter in Au+Au collisions at AGS energy are obtained in the thermal fireball model. The only parameters of the model, the baryon chemical potential and temperature, were determined from a description of the rather complete set of hadron yields from Si+nucleus collisions at the AGS. For the production of light nuclear fragments and strange clusters the results are similar to recent coalescence model calculations. Strange matter production with baryon number larger than 10 is predicted to be much smaller than any current experimental sensitivities.Comment: 9 Pages (no figures

Acoustic propulsion of metallic nano-cylinders: contribution of the local vertical acceleration from micro to hyper gravity

International audienc

What information can we obtain from the yield ratio π−/π+\pi^-/\pi^+ in heavy-ion collisions ?

The recently reported data on the yield ratio $\pi^-/\pi^+$ in central rapidity region of heavy-ion collisions are analyzed by theoretical formula which accounts for Coulomb interaction between central charged fragment (CCF) consisting of nearly stopped nucleons with effective charge Z_{\mbox{\scriptsize eff}} and charged pions produced in the same region of the phase space. The Coulomb wave function method is used instead of the usual Gamow factor in order to account for the finite production range of pions, $\beta$. For Gaussian shape of the pion production sources it results in a quasi-scaling in $\beta$ and Z_{\mbox{\scriptsize eff}} which makes determination of parameters $\beta$ and Z_{\mbox{\scriptsize eff}} from the existing experimental data difficult. Only sufficiently accurate data taken in the extreme small $m_{\scriptscriptstyle T}$-$m_{\pi}$ region, where this quasi-scaling is broken, could be used for this purpose.Comment: 7 pages, Latex type, 8 figure

Open Charm Enhancement in Pb+Pb Collisions at SPS

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. We find a strong enhancement of the open charm production, by a factor of about 2--4, over the standard hard-collision model extrapolation from nucleon-nucleon to nucleus-nucleus collisions. A possible mechanism of the open charm enhancement in A+A collisions at the SPS energies is proposed.Comment: 4 pages, Late

Open and Hidden Charm Production in Heavy Ion Collisions at Ultrarelativistic Energies

We consider the production of the open charm and J/psi mesons in heavy ion collisions at BNL RHIC. We discuss several recently developed pictures for J/psi production and argue that a measurement at RHIC energies is crucial for disentangling these different descriptions.Comment: 19 pages, Latex, 5 PS-figures. v3: Fig.6 is adde

Charmonium Suppression by Comover Scattering in Pb+Pb Collisions

The first reports of $\psi$ and $\psi'$ production from experiment NA50 at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression. Data on centrality dependence and total cross sections are in good accord with these predictions.Comment: 9 pages, latex, 6 figures, epsf, figure added and text modified to clarify result

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 E_T in heavy ion collisions is considered within the statistical c anti-c coalescence model. The model fits the NA50 data for Pb+Pb collisions at the CERN SPS even in the high-E_T region (E_T > 100 GeV). Here E_T-fluctuations and E_T-losses in the dimuon event sample naturally create the celebrated drop in the J/psi to Drell-Yan ratio.Comment: 14 pages, REVTeX, 1 PS-figure. v2: References are corrected and update

Charmonium suppression in p-A collisions

The new high precision data on charmonium production in proton-nucleus collisions by the E866/NuSea collaboration at Fermilab allow - together with older data at lower energies - to fix a unique set of parameters for the standard production and absorption scenario of charmonium in a proton-nucleus reaction. In this scenario the c-cbar pair is formed in an octet state, emits a gluon and continues its radial expansion in a singlet state until it has reached the charmonium radius. In all three phases it can interact with the nuclear environment. We find that the lifetime of the octet state is much shorter than acceptable on physical grounds. This challenges the physical reality of the first phase in the standard scenario.Comment: 8 pages, 10 figure