Parton shower evolution in medium and nuclear modification of photon-tagged jets in Pb+Pb collisions at the LHC

We study the medium modification of jets correlated with large transverse momentum photons at the LHC via a transport and perturbative QCD hybrid model which incorporates the contributions from both elastic collisions and radiative energy loss experienced by the parton showers. Calculations are performed for the modification of the photon-tagged jet yield, the photon-jet energy imbalance, and the azimuthal distribution of away-side jets. The modifications of photon-tagged jets with different $x_T = p_{T, J}/p_{T, \gamma}$ values are studied and they exhibit different centrality and jet cone size dependence due to traversing different medium lengths and density profiles. We further investigate the influence of transverse and longitudinal jet transport coefficients on the nuclear modification of photon-tagged jet production and jet shape observables.Comment: 11 pages, 15 figure

Electromagnetic Radiation from Broken Symmetries in Relativistic Nuclear Collisions

A new channel of direct photon production from a quark gluon plasma (QGP) is explored in the framework of high-temperature QCD. This process appears at next-to-leading order, in the presence of a charge asymmetry in the excited matter. The photon production rate from this new mechanism is suppressed compared to the QCD annihilation and Compton scattering at low baryon density but assumes importance in baryon-rich matter.Comment: 6 pages, 3 figures, Contribution to the Quark Matter 2006 Conference in Shanghai, Nov 14-20 2006, to be submitted to International Journal of Modern Physics E (World Scientific