| Subject: | Quarkonium Hybrid Spectrum in Coulomb Gauge QCD |
| Speaker: | Peng Guo and Adam P. Szczepaniak, Indiana University, Bloomington |
| Date: | Fri., May 16, 2008 |
| Time: | 1:00 p.m., Coffee at 12:45 p.m. |
| Place: | CEBAF Center, Room L104 |
| Abstract: | Using the non-relativistic, Foldy-Wouthousen representation of Coulomb gauge QCD we compute spectrum of low-lying hybrid mesons containing heavy quark-antiquark pair. The gluon degrees of freedom are treated in the mean field approximation calibrated to the gluelump spectrum. We discuss the role of the non-abelian QCD Coulomb interaction in the ordering the spin-parity levels. The coupling scheme of J = J_g + S_{\bar{Q}Q} + L_{\bar{Q}Q} is adopted, which is motivated by the separation of the scales of gluon and quark dynamics, and it corresponds to hybrids being approximately a gluelump-\bar{Q}Q bound state. We give estimates for hyperfine-splittings and compare our results for charmonium and bottomonium spectrum with lattice and data, where available. We find the lowest hybrid charmonium state 1^{−+} should be lighter than 4.48 GeV in agreement with lattice simulation
results.
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| Subject: | Open Charm (D) Mesons in Nuclear Matter at Finite Temperature |
| Speaker: | T. Mizutani, Virginia Tech |
| Date: | Tues., May 20, 2008 |
| Time: | 3:00 p.m. |
| Place: | CEBAF Center L104 |
| Abstract: | Spectral properties of open charm mesons (D and D bar) in finite temperature nuclear matter are studied within a self-consistent coupled-channel scheme. A broken SU(4) extended s-wave Tomozawa-Weinberg type interaction was adopted for the two-body meson-baryon interactions by means of a vector meson exchange picture. The in-medium effects included are Pauli blocking, baryon mean field binding, pion and D-meson self energies. In the DN sector two s-wave charmed baryon resonances, generated in free space, are modified in nuclear matter at finite density and temperature. The resulting D meson in-medium width spread to lower energies due to coupling to charmed baryon resonance-nucleon hole states in combination with temperature-spread nucleon Fermi sea. We discuss its possible effect in relativistic heavy ion collisions, in particular for the future experiment at FAIR (GSI).
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