Studies of medium modifications of light vector mesons in Nuclei

por Chaden Djalali (University of South Carolina)

jueves 2 abr. 2009 16:00 → 17:00 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

The properties of vector mesons, such as their masses and their widths, are predicted to change in dense nuclear matter. Some theoretical models relate these effects to partial restoration of chiral symmetry at high density or temperature. Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The data were taken with a beam of tagged photons with energies up to 4 GeV on various nuclear targets. The properties of the rho vector mesons were investigated via their rare leptonic decay to e+e-. This decay channel is preferred over hadronic modes in order to eliminate final state interactions in the nuclear matter. The combinatorial background in the mass spectrum was removed by a self-normalizing mixed-event technique. The rho meson mass distributions were extracted for each of the targets. Statistically significant results regarding medium modification of the rho meson in the nuclear medium rule out large medium effects. Transparency studies of the omega and phi vector mesons allows a determination of their widths in the medium.