High-energy heavy ion collisions provide an opportunity to study the properties of the hot and dense nuclear matter. In the conditions of extreme temperature and/or density, quarks and gluons, normally confined inside hadronic matter, become deconfined and form a state of matter which we call the quark-gluon plasma. Electron-positron pairs, dielectrons, are created during the whole space-time evolution of the system. Since they don’t interact strongly and leave the medium without final state interactions, dielectrons carry information about the properties of matter at the time of their production. In this thesis the analysis of e+e- pairs from Au+Au collisions at √sNN = 62 GeV was presented, for data collected during 2010 in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). Prior to analysis, the Drift Chamber fiducal cuts were defined and the timing callibration of the Electromagnetic Calorimeter was done. The obtained time-of-flight information was used to define the mass squared variable of the particle, which was then sigmatized as a function of transverse momentum and used in electron identification (eID). After applying eID cuts on the trajectories from runs which have passed the QA (quality assurance) analysis, an electron sample was obtained, with an estimated hadronic background of 15%. Trajectories from the sample were used to form e+e- pairs. After background subtraction, the dielectron invariant mass spectrum was obtained and contributions to the spectrum were discussed. In conclusion, an overlook for the further analysis was given.