Dielectron production in 12C+12C collisions at 2 AGeV with HADES

Dielectron production in 12C+12C collisions at 2 AGeV with HADES

Agakichiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bertini, D.; Bielcik, J.; Bellia, G.; Böhmer, M.; Bokemeyer, H.; Boyard, J. L.; Braun-Munziger, P.; Cabanas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Cosentino, L.; Diaz, J.; Dohrmann, F.; Duran, I.; Eberl, T.; Enghardt, W.; Fabbietti, L.; Fateev, O.; Fernandez, G.; Finocchiaro, P.; Friese, J.; Fröhlich, I.; Fuentes, B.; Garabatos, C.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Gonzalez-Diaz, D.; Grosse, E.; Guber, F.; Hennino, T.; Hlavac, S.; Holzmann, R.; Homolka, J.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jaskula, M.; Jurkovic, M.; Kargalis, M.; Kajetanowicz, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kastenmüller, A.; Kidon, L.; Kienle, P.; Koenig, I.; Koenig, W.; Körner, H. J.; Kolb, B. W.; Kotte, R.; Krücken, R.; Kugler, A.; Kühn, W.; Kulessa, R.; Kurepin, A.; Lang, S.; Lange, S.; Lehnert, J.; Lins, E.; Magestro, D.; Maiolino, C.; Malarz, A.; Markert, J.; Metag, V.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Nekhaev, A.; Novotny, J.; Otwinowski, J.; Pachmayer, Y.; Pechenov, V.; Perez, T.; Piattelli, P.; Pietraszko, J.; Pleskac, R.; Ploskon, M.; Pospisil, V.; Prokopovicz, W.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Ritman, J.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sanchez, M.; Sapienza, P.; Schmah, A.; Schön, H.; Schön, W.; Simon, R. S.; Smolyankin, V.; Smykov, L.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Strurm, C.; Sudol, M.; Suk, M.; Taranenko, A.; Tlusty, P.; Toia, A.; Traxler, M.; Tsertos, H.; Vassiliev, D.; Vazquez, A.; Wagner, V.; Walus, W.; Wisniovski, M.; Wojcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Zeitelhack, K.; Zoviec, D.; Zumbruch, P.

The invariant mass spectrum of e^+ e^- pairs produced in ^{12}C+^{12}C collisions at 2 GeV per nucleon incident energy has been measured for the first time with the HADES spectrometer at GSI. The measured pair production probabilities span over five orders of magnitude within the \pi^0\to e^+e^-\gamma to \rho/\omega\to e^+e^- invariant mass region. A thermal model of the dielectron sources underestimates the measured probabilities by a factor of roughly two at intermediate masses (0.2 -- 0.6 GeV/c^2) whereas it overshoots data at the \rho/\omega pole. Transport model calculations assuming vacuum spectral functions of the vector mesons fail to describe the entire invariant mass spectrum, as well.

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