UC Berkeley

Prompt photons, produced via QCD Compton scattering or quark and anti-quark annihilation at leading order, are unique probes to study QCD processes since they do not interact strongly and therefore allow to control the dynamics of the initial hard parton scattering. Isolated photon production in pp collisions is one of the most clear tests of perturbative QCD processes and parton distribution functions. Photon measurement in p–A collisions provides the opportunity to measure possible modifications of the nucleon structure function in nuclei. ALICE has measured isolated photons at low pT, thus extending previous measurements down to small x. In this thesis, the cross section of isolated photons for the range 12 GeV/c < pT < 60 GeV/c is presented in pp and p–Pb collisions at √sNN = 5.02 TeV along with photon nuclear modification factor (RpPb).