Study of inclusive elektron-positron pair production in collisions of Ar+Kcl at 1.756 A GeV

Title: Study of inclusive electron-positron pair production in collisions of Ar + KC1 at 1.756 AGeV Author: Mgr. Filip Kfi'zek, Ph.D. Abstract: Spectroscopy of di-leptons emerging in decays of the light vector mesons př, CD, and ^ is a promising way how to investigate changes of properties of these hadrons in the surrounding nuclear environment. This thesis deals with an analysis of inclusive e"V pair emission from. Ar+KCl collisions at a kinetic beam energy of 1.756 AGeV. The measurement was carried out using the High Acceptance Di-Electron Spectrometer (HADES). HADES is a unique apparatus dedicated to study e+e~ pair production in hot and dense hadronic matter. After an introduction to the field, the HADES spectrometer is briefly described. Then we focus on the analysis of the Ar+KCl run. We describe and discuss event selection performed by the on-line trigger, lepton identification, and the subsequent pair analysis. Efficiency corrected spectra of parrs are compared with predictions of a thermal model based Monte Carlo event generator (Pluto) and, further, with forecasts of a microscopic transport code (HSD). Finally, we compare results from the HADES Ar+KCl and C+C runs. With respect to the expected di-electron yield from i\-> y e e" decay, in the invariant mass region 0.15 - 0.50 GeV/c2, our spectra..