Origin of the low-mass electron pair excess in light nucleus–nucleus collisions

详细信息    查看全文

• 作者：HADES Collaboration ; G. Agakichiev ; A. Bal ; a ; D. Belver ; A.V. Belyaev ; A. Blanco ; M. Bö ; hmer ; J.L. Boyard ; P. Braun-Munzinger ; P. Cabanelas ; E. Castro ; S. Chernenko ; T. Christ ; M. Destefanis ; J. D
• 关键词：Virtual bremsstrahlung ; Dileptons ; Nucleon– ; nucleon collisions
• 刊名：Physics Letters B
• 出版年：2010
• 出版时间：14 June 2010
• 年：2010
• 卷：690
• 期：2
• 页码：118-122
• 全文大小：269 K

文摘

We report measurements of electron pair production in elementary p+p and d+p reactions at 1.25 GeV/u with the HADES spectrometer. For the first time, the electron pairs were reconstructed for n+p reactions by detecting the proton spectator from the deuteron breakup. We find that the yield of electron pairs with invariant mass M_e⁺e⁻>0.15 GeV/c² is about an order of magnitude larger in n+p reactions as compared to p+p. A comparison to model calculations demonstrates that the production mechanism is not sufficiently described yet. The electron pair spectra measured in C+C reactions are compatible with a superposition of elementary n+p and p+p collisions, leaving little room for additional electron pair sources in such light collision systems.