Dielectron Production in $^{12}$C+$^{12}$C Collisions at 2A GeV with the HADES Spectrometer

G. Agakichiev , C. Agodi , H. Alvarez-Pol , A. Balanda , D. Bertini , J. Bielcik , G. Bellia , M. Böhmer , H. Bokemeyer , J.L. Boyard (1) , P. Braun-Munzinger , P. Cabanelas , S. Chernenko , T. Christ , R. Coniglione , L. Cosentino , J. Diaz , F. Dohrmann , I. Durán , T. Eberl , W. Enghardt , L. Fabbietti , O. Fateev , C. Fernandez , P. Finocchiaro , J. Friese , I. Fröhlich , B. Fuentes , C. Garabatos , J. A. Garzón , R. Gernhäuser , C. Gilardi , M. Golubeva , D. González-Díaz , E. Grosse , F. Guber , T. Hennino (1) , S. Hlavac , R. Holzmann , J. Homolka , A. Ierusalimov , I. Iori , A. Ivashkin , M. Jaskula , M. Jurkovic , M. Kagarlis , M. Kajetanowicz , B. Kämpfer , K. Kanaki , T. Karavicheva , A. Kastenmüller , L. Kidoń , P. Kienle , I. Koenig , W. Koenig , H. J. Körner , B. W. Kolb , R. Kotte , R. Krücken , A. Kugler , W. Kühn , R. Kulessa , A. Kurepin , S. Lang , S. Lange , J. Lehnert , E. Lins , D. Magestro , C. Maiolino , A. Malarz , J. Markert , V. Metag , J. Mousa , M. Münch , C. Müntz , L. Naumann , A. Nekhaev , J. Novotny , J. Otwinowski , Y. C. Pachmayer , V. Pechenov , T. Pérez , P. Piattelli , J. Pietraszko , R. Pleskac , M. Ploskoń , V. Pospísil , W. Prokopowicz , W. Przygoda , B. Ramstein (1) , A. Reshetin , J. Ritman , M. Roy-Stephan (1) , A. Rustamov , A. Sadovsky , B. Sailer , P. Salabura , M. Sánchez , P. Sapienza , A. Schmah , H. Schön , W. Schön , C. Schröder , E. Schwab , R. S. Simon , V. Smolyankin , L. Smykov , S. Spataro , B. Spruck , H. Ströbele , J. Stroth , C. Sturm , M. Sudol , M. Suk , A. Taranenko , P. Tlusty , A. Toia , M. Traxler , H. Tsertos , D. Vassiliev , A. Vázquez , V. Wagner , W. Walus , M. Wisniowski , T. Wójcik , J. Wüstenfeld , Y. Zanevsky , K. Zeitelhack , D. Zovinec , P. Zumbruch

1 IPNO - Institut de Physique Nucléaire d'Orsay

The invariant-mass spectrum of e+e- pairs produced in 12C+12C collisions at an incident energy of 2 GeV per nucleon has been measured for the first time. The measured pair production probabilities span over 5 orders of magnitude from the pi0-Dalitz to the rho/omega invariant-mass region. Dalitz decays of pi0 and eta account for all the yield up to 0.15 GeV/c2, but for only about 50% above this mass. A comparison with model calculations shows that the excess pair yield is likely due to baryon-resonance and vector-meson decays. Transport calculations based on vacuum spectral functions fail, however, to describe the entire mass region.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

G. Agakichiev, C. Agodi, H. Alvarez-Pol, A. Balanda, D. Bertini, et al.. Dielectron Production in $^{12}$C+$^{12}$C Collisions at 2A GeV with the HADES Spectrometer. Physical Review Letters, 2007, 98, pp.052302. ⟨10.1103/PhysRevLett.98.052302⟩. ⟨in2p3-00129072⟩