Fotoprodução de Pares de Léptons em Colisões Próton-Núcleo e Núcleo-Núcleo no Grande Colisor de Hádrons.

Abstract

One of the first issues addressed by Quantum Electrodynamics was the production of electron-positron pairs in photon - nucleus and nucleus - nucleus collisions. These studies demonstrated that the cross section is large and that Coulomb corrections associated with multiple exchange of photons become important when heavy nuclei are present. More recently, with the advent of the accelerators RHIC (Relativistic Heavy Ion Collider) and LHC (Large Hadron Collider), which collide heavy ions, this problem was addressed by several authors, which extended the previous studies for the production of muon pairs and estimated the effects of unitarity in the kinematical regime of the accelerators. Our goal in this dissertation is to review the production of lepton pairs in ultraperipheral collisions considering the Weiszacker-Williams approach and the dipole formalism and estimate the rate of lepton pair production in proton - nucleus and nucleus - nucleus collisions for the RHIC and LHC energies. In particular, we estimate, for the first time, the production of taus AA in collisions and heavy leptons pairs leptons in pA collisions. Our studies show that the Coulomb corrections are large for the production of electron in pA and AA collisions, small for the production of heavy leptons in AA collisions and negligible in pA collisions. Furthermore, our results demonstrate that the muon pair production is large in proton - nucleus collisions, which implies that the experimental analysis of this process is feasible in the LHCb experiment.