Origin of the low-mass electron pair excess in light nucleus-nucleus collisions
Abstract
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 Me+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.
Keywords
Cite
@article{arxiv.0910.5875,
title = {Origin of the low-mass electron pair excess in light nucleus-nucleus collisions},
author = {The HADES Collaboration and G. Agakishiev and A. Balanda and D. Belver and A. V. Belyaev and A. Blanco and M. Böhmer and J. L. Boyard and P. Braun-Munzinger and P. Cabanelas and E. Castro and S. Chernenko and T. Christ and M. Destefanis and J. Díaz and F. Dohrmann and A. Dybczak and L. Fabbietti and O. V. Fateev and P. Finocchiaro and P. Fonte and J. Friese and I. Fröhlich and T. Galatyuk and J. A. Garzón and R. Gernhäuser and A. Gil and C. Gilardi and M. Golubeva and D. González-Díaz and F. Guber and T. Hennino and R. Holzmann and I. Iori and A. Ivashkin and M. Jurkovic and B. Kämpfer and T. Karavicheva and D. Kirschner and I. Koenig and W. Koenig and B. W. Kolb and R. Kotte and F. Krizek and R. Krücken and W. Kühn and A. Kugler and A. Kurepin and S. Lang and J. S. Lange and K. Lapidus and T. Liu and L. Lopes and M. Lorenz and L. Maier and A. Mangiarotti and J. Markert and V. Metag and B. Michalska and J. Michel and E. Morinière and J. Mousa and C. Müntz and L. Naumann and J. Otwinowski and Y. C. Pachmayer and M. Palka and Y. Parpottas and V. Pechenov and O. Pechenova and J. Pietraszko and W. Przygoda and B. Ramstein and A. Reshetin and A. Rustamov and A. Sadovsky and P. Salabura and A. Schmah and E. Schwab and Yu. G. Sobolev and S. Spataro and B. Spruck and H. Ströbele and J. Stroth and C. Sturm and M. Sudol and A. Tarantola and K. Teilab and P. Tlusty and M. Traxler and R. Trebacz and H. Tsertos and V. Wagner and M. Weber and M. Wisniowski and T. Wojcik and J. Wüstenfeld and S. Yurevich and Y. V. Zanevsky and P. Zhou},
journal= {arXiv preprint arXiv:0910.5875},
year = {2014}
}
Comments
11 pages, 2 figures, \usepackage{epsfig}