First measurement of proton-induced low-momentum dielectron radiation off cold nuclear matter

0384317 - ÚJF 2013 RIV NL eng J - Journal Article
Agakishiev, G. - Balanda, A. - Belyaev, A. - Finocchiaro, P. - Guber, F. - Karavicheva, T. - Krása, Antonín - Křížek, Filip - Kugler, Andrej - Markert, J. - Michel, J. - Pechenova, O. - Rustamov, A. - Sobolev, Yuri, G. - Strobele, H. - Tarantola, A. - Teilab, K. - Tlustý, Pavel - Wagner, Vladimír … Total 98 authors
First measurement of proton-induced low-momentum dielectron radiation off cold nuclear matter.
Physics Letters. B. Roč. 715, 4-5 (2012), s. 304-309. ISSN 0370-2693. E-ISSN 1873-2445
R&D Projects: GA MŠMT LC07050; GA AV ČR IAA100480803
Keywords : vector-mesons * Rho-meson * collisions
Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders
Impact factor: 4.569, year: 2012

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 P-ee < 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.
Permanent Link: http://hdl.handle.net/11104/0214012