e+e−pair production fromγAreactions

Abstract

We present a calculation of e + e − production in γA reactions at MAMI and TJNAF energies within a semi-classical BUU transport model. Dilepton invariant mass spectra for γC, γCa and γPb are calculated at 0.8, 1.5 and 2.2 GeV. We focus on observable effects of medium modifications of the ρ and ω

Perspectives of production in , and Be reactions at SIS energies

“…[33]), whereas in the present approach we assume that the ρ meson has a free spectral function with masses only above 2m π . The latter assumption leads to the 'direct ρ decay' profile for dileptons from subthreshold ρ's and is consistent with our resonance prescription used also in the transport calculations [35], where we propagate such ρ mesons explicitly.…”

“…This assumption provides not only a significant simplification, which is necessary for applications in transport calculations [25,42,35], but also allows to take into account the 'inelasticity' from many-particle production channels which become dominant at high energy.…”

“…[35,36]. This model is based on the resonance concept of nucleon-nucleon and meson-nucleon interactions at low invariant energy √ s [37] by adopting all resonance parameters from the Manley analysis [38]; all states with at least 1 For a detailed description of the individual channels we refer the reader to Ref.…”

“…The collisional dynamics for proton-nucleus reactions, furthermore, is described by the coupled-channel BUU transport approach [35,36] that is based on the same elementary cross sections.…”

“…We investigate the role of isospin degrees of freedom with respect to dilepton production in pd reactions by employing exact energy-momentum conservation for the deuteron target. The pBe reactions are calculated within the resonance transport model [35] that includes the same elementary production amplitudes.…”