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Heavy Flavor Productions & Hot/Dense Quark Matter
Date: December 12-14, 2005
Motivation and Plans for the Workshop
There is growing evidence that high density partonic matter is formed in heavy ion collision at RHIC. Heavy flavor production, open and hidden, is considered among the most important probes for discovery and for study of QCD properties of the QGP. We propose to have a workshop that summarizes the present status of experiment and theory on heavy flavor production in p+p, p+A, and A+A collisions, and discuss heavy flavor as probes of the hot and dense matter created at RHIC.
In 1986, T. Matsui and H. Satz predicted that the J/Psi production would be significantly suppressed in relativistic heavy-ion collisions compared to that in p+p or p+A collisions due to the Debye screening effect. They suggest that the observation of a large suppression is an unambiguous signature of the QGP formation. Recent theoretical progress has made the picture somewhat more complicated. Lattice calculations indicate that J/Psi will not disassociate until reaching the temperature a factor of two above critical temperatures. Several authors (R. Thews et al., P. Braun-Munzinger et al., and R. Rapp et al.) proposed various kinds of recombination mechanisms of J/Psi formation from charm and anti-charm pairs, and some of them even predicted enhancement of the J/Psi production when QGP is formed. These different models are consistent with the PHENIX J/Psi results in RUN2002 due to its lack of statistics. It is also important to distinguish dissociation of J/Psi in a hot medium from a similar effect in the Color Glass Condensate in order to have an unambiguous argument about the QGP formation. High statistics data are therefore needed to determine the J/Psi production mechanism in the medium.
Open heavy flavor is an important probe of the dense matter formed in heavy ion collisions. In heavy-ion collisions at RHIC, the production of high pT particles is strongly suppressed. The suppression is considered as being due to energy loss of light quarks in the dense medium formed in the collision. There are theoretical predictions that the energy loss of heavy quarks is smaller due to "dead cone effect" (D. Kharzeev et al.) and "Ter-Mikayelian" effect (M. Djordjevic et al.). The first data on open charm production from PHENIX in p+p, d+Au, and Au+Au and STAR in p+p and d+Au at RHIC have been reported, but the present PHENIX data in Au+Au are not sufficient to determine if energy loss of charm is indeed smaller than that for light quarks. It would be essential for the understanding of the medium characteristic that we investigate how heavy quarks behave differently from light quarks using high statistics data.
There are other important issues on the charm production at RHIC. Open charm production is crucial input for the recombination models of the J/Psi production. Open charm can be produced in the pre-equilibrium stage of the hot dense matter. The difference of open charm at central and forward rapidity can be an important signature of the formation of Color-Glass Condensate, as D. Kharzeev and K. Tuchin predicted. It would be also very interesting to learn about possible transitions and their locations in pT from thermal to coalescence to pQCD energy loss for both open and hidden heavy flavor, similar to what appears to be emerging from light hadrons.
In year 2004, RHIC had a dedicated Au+Au run to answer the above questions. Almost a factor of 50 more Au+Au collisions are recorded compared to the run in 2002. PHENIX and STAR experiment are expected to show their results with much higher precision at Quark Matter 2005. We expect these results will inspire a lot of theoretical activities trying to understand the data in the following few months after the conference. We therefore propose a workshop 2 or 3 months after the conference and invite top physicists in this area to discuss their understanding of the heavy flavor production in the hot/dense quark matter produced at RHIC and hope to accomplish a clearer picture of these important issues.
Last Modified: February 5, 2008