First measurement of low momentum dielectrons radiated off cold nuclear matter
Abstract
We present data on dielectron emission in proton induced reactions on a Nb target at 3.5 GeV kinetic beam energy measured with HADES installed at GSI. The data represent the first high statistics measurement of proton-induced dielectron radiation from cold nuclear matter in a kinematic regime, where strong medium effects are expected. Combined with the good mass resolution of 2%, it is the first measurement sensitive to changes of the spectral functions of vector mesons, as predicted by models for hadrons at rest or small relative momenta. Comparing the e+e invariant mass spectra to elementary p+p data, we observe for e+e momenta Pee < 0.8 GeV/c a strong modification of the shape of the spectrum, which we attribute to an additional rho-like contribution and a decrease of omega yield. These opposite trends are tentatively interpreted as a strong coupling of the rho meson to baryonic resonances and an absorption of the omega meson, which are two aspects of in-medium modification of vector mesons.
Keywords
Cite
@article{arxiv.1205.1918,
title = {First measurement of low momentum dielectrons radiated off cold nuclear matter},
author = {G. Agakishiev and A. Balanda and D. Belver and A. Belyaev and J. C. Berger-Chen and A. Blanco and M. Böhmer and J. L. Boyard and P. Cabanelas and S. Chernenko and A. Dybczak and E. Epple and L. Fabbietti and O. Fateev and P. Finocchiaro and P. Fonte and J. Friese and I. Fröhlich and T. Galatyuk and J. A. Garzón and R. Gernhäuser and K. Göbel and M. Golubeva and D. González-Díaz and F. Guber and M. Gumberidze and T. Heinz and T. Hennino and R. Holzmann and A. Ierusalimov and I. Iori and A. Ivashkin and M. Jurkovic and B. Kämpfer and T. Karavicheva and I. Koenig and W. Koenig and B. W. Kolb and G. Kornakov and R. Kotte and A. Krása and F. Krizek and R. Krücken and H. Kuc and W. Kühn and A. Kugler and A. Kurepin and V. Ladygin and R. Lalik and S. Lang and K. Lapidus and A. Lebedev 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 D. Mishra and C. Müntz and L. Naumann 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 J. Siebenson and Yu. G. Sobolev and S. Spataro and B. Spruck and H. Ströbele and J. Stroth and C. Sturm and A. Tarantola and K. Teilab and P. Tlusty and M. Traxler and R. Trebacz and H. Tsertos and T. Vasiliev and V. Wagner and M. Weber and C. Wendisch and J. Wüstenfeld and S. Yurevich and Y. Zanevsky},
journal= {arXiv preprint arXiv:1205.1918},
year = {2012}
}