Pion Cloud Contribution in Production of Leptons in Nuclear Collisions

In deep inelastic collision of two hadrons, clumps of particles are produced that among these particles can be noted the simultaneous production of lepton and its anti through a process called Drell - Yan. The study of dileptons produced through the Drell - Yan process can provide information on how the quark distribution inside the nuclei and consequently their internal structure, as well as the effects of the nuclear environment on them. In this thesis, with a selection of the proton as projectiles and heavy nuclei of copper and platinum as target, the contribution of the pion cloud between the bound nucleon inside the nucleus in the production of lepton pairs was studied, and the obtained theoretical results were compared with the available experimental results and analyzed. The study method is the measurement of dilepton production cross section once, regardless of the pion cloud and again by taking it. For this purpose, library studies were done and the necessary mathematical relations were extracted. In order to investigation of the pion cloud contribution in dilepton production cross section beside the nucleons contribution, FORTRAN program was written and by applying free nucleon and free pion quark distribution functions, the distribution functions of valence and sea quarks inside the projectile and target nucleus were calculated once, based on the shell model and again based on the Fermi gas model. Then, using the Drell - Yan formulation, calculation of lepton pair production cross section was performed. Finally, the theoretical data obtained through the Numerical Fortran program were compared with the experimental results and contribution of the pion cloud in dilepton production cross section was obtained.