%0 Generic
%A Yurevich, Sergey
%D 2006
%F heidok:6558
%K CERES , Elektronenpaaren , ioneninduzierten Kollisionen , Dileptonenpaaren , TPC , $\rho$-Meson , NA45 , SPS , CERNHeavy Ion physics dileptons , electron pair , CERES , NA45 , QGP , production , TPC , RICH , SDD , electron identification , track finding
%R 10.11588/heidok.00006558
%T Electron-Pair Production in 158 AGeV/c  Pb-Au Collisions from CERES
%U https://archiv.ub.uni-heidelberg.de/volltextserver/6558/
%X The CERES experiment is devoted to the measurement of  low-mass electron pairs in proton and ion-induced collisions at the  Super Proton Synchrotron accelerator. The main goal of the CERES experiment is to investigate modifications of hadron properties in  hot and dense nuclear matter. A significant enhancement of  dilepton pair yield with respect to expectations based on hadron decays was observed in the mass range 0.25~$<~$m$_{ee}~<$~0.7~GeV/c$^2$. This fascinating result can only be described by models invoking in-medium modifications of the $\rho$ meson. To distinguish between different theoretical explanations of the enhancement the experiment was upgraded in 1998 by the addition of a radial TPC to improve the mass resolution in the vector meson region. In this thesis, the analysis of the data sample taken in 2000 in 158~A~GeV/c Pb-Au collisions with the upgraded experimental setup  is presented. The observed enhancement of the $e^+e^-$ pairs confirms  previous results of CERES. The data, compared to the theoretical calculations based on dropping $\rho$ mass approach and in-medium $\rho$ spectral function modifications, favor the latter.