Identification of particles and hard processes with the spectrometer PHOS of the ALICE experiment

Heavy-ion collisions are a unique tool to study nuclear matter under extreme conditions of density and temperature like the ones present a few moments after the Big Bang, where nuclear matter may be composed of a plasma of almost free quarks and gluons. Its production is the main interest of the ALICE experiment at the LHC collider, where Pb-Pb collisions at 5.5A TeV will be made. Photons are an interesting signature produced in these collisions as they can give unperturbed information on their creation conditions. The PHOS detector in the ALICE experiment is devoted to their measurement. For this thesis a PHOS performance study and the development of particle identification algorithms have been done. High-energy photons will be produced with a recoiling jet which can suffer modifications due to the nuclear medium produced, an identification method of such processes is described and its sensitivity to jet modifications induced by the nuclear medium is studied.