{"id":{"repo_id":"heid-diss","oai_identifier":"oai:archiv.ub.uni-heidelberg.de:6558"},"canonical_url":"https://search.dev.ndltd.org/etd/heid-diss/oai:archiv.ub.uni-heidelberg.de:6558","repository":{"repo_id":"heid-diss","name":"Universität Heidelberg","base_url":"http://archiv.ub.uni-heidelberg.de/volltextserver/cgi/oai2"},"display":{"title":"Electron-Pair Production in 158 AGeV/c Pb-Au Collisions from CERES","abstract":"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.","abstract_html":"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~$&lt;~$m<span class=\"etd-inline-math\"><sub>ee</sub>~&lt;</span>~0.7~GeV/c<span class=\"etd-inline-math\"><sup>2</sup></span>. 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 <span class=\"etd-inline-math\">e<sup>+</sup>e<sup>-</sup></span> 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.","abstract_has_math":true,"creators":["Yurevich, Sergey"],"institution":"Universität Heidelberg","degree_name":null,"degree_level":"thesis.doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Stachel, Johanna"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006-05-10","date_published":"2006-05-10","updated_at":"2026-07-24T02:30:27Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://www.ub.uni-heidelberg.de/archiv/6558","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Stachel, Johanna"]},{"key":"dc:creator","label":"Author","values":["Yurevich, Sergey"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:publisher","label":"Institution","values":["Universitätsbibliothek Heidelberg"]},{"key":"dc:type","label":"Dc Type","values":["doctoralThesis"]},{"key":"thesis:degree_level","label":"Degree Level","values":["thesis.doctoral"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Universität Heidelberg"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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.","Das CERES Experiment besch\\\"aftigt sich mit der Messung von Elektronenpaaren im niederen Massenbereich in protonen- und ioneninduzierten Kollisionen am Super Proton Synchrotron. Im Mittelpunkt steht dabei die Untersuchung von Ver\\\"anderungen hadronischer Eigenschaften unter dem Einflu{\\ss} hei{\\ss}er und dichter Kernmaterie. Eine signifikant erh\\\"ote Produktionsrate von Dileptonenpaaren, bezogen auf Erwartungen aus hadronischen Zerf\\\"allen, wurde im Massenbereich \\mbox{$0.25 < m_{ee} < 0.7$ GeV/c$^{2}$} beobachtet. Dieses faszinierende Ergebnis kann nur durch Modelle erkl\\\"art werden, die Ver\\\"anderungen des $\\rho$-Mesons innerhalb des Mediums zulassen. Um eine bessere Massenaufl\\\"osung im Bereich der Vektormesonen zu erreichen und somit zwischen den verschiedenen theoretischen Erkl\\\"arungsm\\\"oglichkeiten unterscheiden zu k\\\"onnen, wurde das Experiment im Jahr 1998 durch eine TPC mit radialer Drift erg\\\"anzt. Die in dieser Doktorarbeit vorgestellte Analyse beruht auf dem Datensatz von 158 A GeV/c Pb-Au Kollisionen, der im Jahr 2000 mit dem erweiterten experimentellen Aubau aufgenommenen wurde. Die beobachtete erh\\\"ohte Produktionsrate der $e^{+}e^{-}$-Paare best\\\"atigt fr\\\"uhere CERES Ergebnisse. Ein Vergleich der Daten mit theoretischen Vorhersagen favorisiert Rechnungen, die auf der Ver\\\"anderung der Spektralfunktion des $\\rho$-Mesons im Medium beruhen, gegen\\\"uber solchen, die auf einer reduzierten $\\rho$-Mesonen Masse beruhen."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Electron-Pair Production in 158 AGeV/c Pb-Au Collisions from CERES","Elektronen-Paar-Produktion in 158 AGeV/c Pb-Au Kollisionen bei CERES"]}]}],"canonical_facts":{"dc:contributor":["Stachel, Johanna"],"dc:creator":["Yurevich, Sergey"],"dc:description.abstract":["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.","Das CERES Experiment besch\\\"aftigt sich mit der Messung von Elektronenpaaren im niederen Massenbereich in protonen- und ioneninduzierten Kollisionen am Super Proton Synchrotron. Im Mittelpunkt steht dabei die Untersuchung von Ver\\\"anderungen hadronischer Eigenschaften unter dem Einflu{\\ss} hei{\\ss}er und dichter Kernmaterie. Eine signifikant erh\\\"ote Produktionsrate von Dileptonenpaaren, bezogen auf Erwartungen aus hadronischen Zerf\\\"allen, wurde im Massenbereich \\mbox{$0.25 < m_{ee} < 0.7$ GeV/c$^{2}$} beobachtet. Dieses faszinierende Ergebnis kann nur durch Modelle erkl\\\"art werden, die Ver\\\"anderungen des $\\rho$-Mesons innerhalb des Mediums zulassen. Um eine bessere Massenaufl\\\"osung im Bereich der Vektormesonen zu erreichen und somit zwischen den verschiedenen theoretischen Erkl\\\"arungsm\\\"oglichkeiten unterscheiden zu k\\\"onnen, wurde das Experiment im Jahr 1998 durch eine TPC mit radialer Drift erg\\\"anzt. Die in dieser Doktorarbeit vorgestellte Analyse beruht auf dem Datensatz von 158 A GeV/c Pb-Au Kollisionen, der im Jahr 2000 mit dem erweiterten experimentellen Aubau aufgenommenen wurde. Die beobachtete erh\\\"ohte Produktionsrate der $e^{+}e^{-}$-Paare best\\\"atigt fr\\\"uhere CERES Ergebnisse. Ein Vergleich der Daten mit theoretischen Vorhersagen favorisiert Rechnungen, die auf der Ver\\\"anderung der Spektralfunktion des $\\rho$-Mesons im Medium beruhen, gegen\\\"uber solchen, die auf einer reduzierten $\\rho$-Mesonen Masse beruhen."],"dc:format.medium":["application/pdf"],"dc:publisher":["Universitätsbibliothek Heidelberg"],"dc:title":["Electron-Pair Production in 158 AGeV/c Pb-Au Collisions from CERES","Elektronen-Paar-Produktion in 158 AGeV/c Pb-Au Kollisionen bei CERES"],"dc:type":["doctoralThesis"],"thesis:degree_level":["thesis.doctoral"],"thesis:institution_name":["Universität Heidelberg"]},"updated_at":"2026-07-24T02:30:27Z"}