Gamma-jet physics with the Electro-Magnetic Calorimeter in the ALICE experiment at LHC

The Electro-Magnetic Calorimeter (EMCal) will be fully installed for the first LHC heavy ion beam in order to improve the ALICE experiment performances in detection of high transverse momentum particles and in particular in reconstruction of gamma-jet events. These events appear to be very interesting to probe the strongly interacting matter created in ultra-relativistic heavy ion collisions and the eventual Quark Gluon Plasma (QGP) state. Indeed, they may give information on the degree of medium opacity which induces the jet-quenching phenomenon: measuring the energy of the gamma and comparing it to that of the associated jet may provide a unique way to quantify the jet energy loss in the dense matter. The interest of gamma-jet studies in the framework of the quark gluon plasma physics will be discussed. A particular highlight will be stressed on the EMCal calorimeter. The detection of the gamma-jet events will be then presented using this new ALICE detector.