Charmonium and Bottonium Production in A+A at LHC

by (CERN)

Wednesday 7 Mar 2001, 10:00 → 11:00 Europe/Zurich

TH Auditorium (CERN)

Morning: TH amphitheatre 10:00-11:00 Ramona Vogt Production Rates for c-cbar and b-bar in A+A In this talk, I will first discuss the extent to which the ccbar and bbbar cross sections are known in pp interactions. Then I will discuss effects of nuclear shadowing on the total cross sections. Next, I will describe the effects of energy loss in the finite acceptance of a real detector in a number of lepton pair invariant mass regions and discuss which components (heavy quarks, Drell-Yan) are most important to the dilepton continuum. I will discuss some possible reference processes for quarkonium suppression in light of these results. 11:00-11:30 Jean-Yves Ollitrault (CEA Saclay) Charmonium suppression in central Pb-Pb collisions A recent analysis of Pb--Pb data by the NA50 collaboration shows that the J/psi over Drell-Yan ratio as a function of ET suggests a two-threshold structure: the first threshold, already seen in earlier data, corresponds to the onset of the so-called 'anomalous J/psi suppression', while the second threshold appears at the highest values of ET, corresponding to the most central collisions. I present a simple model of anomalous J/psi suppression which provides a perfect fit to these recent data. This model assumes that the J/psi disappears gradually when the local energy density increases. The second decrease of the J/psi over Drell-Yan ratio is interpreted as an effect of transverse energy fluctuations: the higher the transverse energy, the larger the region where the J/psi's disappear. I also discuss the recently measure pT dependence of J/Psi suppression and present prediction for RHIC. 11:30-12:00 Johanna Stachel (Univ. Heidelberg) Production of charmed hadrons from a hadronizing quark-gluon plasma 12:30-13:00 Mark Gorensteini Statistical models of quarkonia production This talk reports the calculations of charmonia production in nucleus-nucleus collisions assuming that the mechanism for formation of hadrons which contain charm quarks distributes the charm in hadrons according to a statistical prescription, and the total charm available is that produced in the initial hard collisions of hadrons. The statistical coalescence model with an exact charm conservation is considered. From the J/psi multiplicity data in Pb+Pb collisions at 158 AGeV the open charm yield is predicted about a factor 3 above the standard pQCD estimates. The production of open charm and J/psi is discussed also for the RHIC energies. Both the suppression and enhancement effects of the ratio of the J/psi to the open charm in heavy ion collisions are found. We argue that a measurement at RHIC energies is crucial for disentangling between the different descriptions. lunch break Afternoon: 160-1-009 14:00-14:30 14:00-14:30 Olga Kodolova (SINP MSU, Moscow) Heavy Ion studies on CMS The performance of CMS to observe J/psi and upsilon families has been investigated. Resonance cross-sections and secondary particle multiplicities are calculated as a function of the collision impact parameter. An algorithm for the reconstruction of muon pairs produced in heavy ion collisions at LHC energies and detected in the barrel region |eta|<1.3 of the CMS detector has been designed. For central Pb-Pb collisions, an efficiency as high as 75% for the reconstruction of the upsilon(1S)-decay muons can be reached in the pseudorapidity region |eta|<0.8. For min bias efficiency reaches 90%. In the rapidity interval 0.8<|eta|<1.3 the efficiency drops down to 50%. A dimuon mass resolution of 46 MeV is obtained for the reconstructed upsilon. The dimuon mass spectra obtained for one month of data taking are calculated including contribution of different background sources. Statistics and Signal/Background ratios allow to conclude that CMS has good capabilities for these studies. 6) 14:30-15:00 Nicola Carrer (CERN) New estimate of heavy-flavour production rates for ALICE simulations The heavy-flavour production cross sections at sqrt(s)=5.5TeV, at the time of the ALICE technical proposal, had large uncertainties mainly due to the poor knowledge of PDFs in the small x regime. These uncertainties are substantially reduced and a more reliable estimate is obtained when one takes into account the present knowledge of PDFs, coming mainly from the HERA data at low x and from the inclusion of nuclear shadowing effects. An estimate of the c-cbar and b-bbar cross sections obtained using pythia and the EKS parametrisation for the shadowing will be presented. 7) 15:00-15:30 Jean Gosset (Saclay) Normalization of quarkonium production to the inclusive centrality distribution of cross section 8) 15:00-15:30 Philippe Crochet (Univ. Blaise Pascal, IN2P3/CNRS Heavy quarkonia with ALICE: detector capabilities and data Analysis The expected performances of the ALICE detector for the measurement of heavy quarkonia are reviewed. Special emphasis is placed on some open questions about the extraction of relevant information from the data. 9) 16:00-16:30 Discussion Input into ALICE-PPR

Organiser(s): Yiota Foka, Urs Wiedemann and Guy Paic

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