Produção de diléptons em colisões de íons pesados no grande colisor de hádrons

Abstract

The photon induced processes at LHC are an important tool to study exclusive processes both in photon-hadron and in photon-photon interactions. In this dissertation we have studied the dileptons production due to γγ interactions in ultrarelativistic heavy-ion col lisions. These ions generate strong electromagnetic fields that may be treated as a flux of virtual photons through the equivalent photon approximation. We estimate the rapidity and invariant mass distributions of the dileptons in ultraperipheral collisions at the RHIC and LHC energies. Such collisions are characterized by an impact parameter greater than the sum of the radius of the incident nuclei, which implies the suppression of the strong interactions and the dominance of the electromagnetic interaction between them. We have consider different levels of precision for the treatment of the absorptive factor S 2 abs and for the nuclear form factor F. In particular, we implement the kinematical cuts in order to compare our predictions with recent data of the ALICE and ATLAS Collaborations for the exclusive e +e − and µ +µ − production by γγ interactions in lead-lead collisions with mass center energies of √ s = 2.76 TeV and √ s = 5.02 TeV, respectively.