Probing Hadronic Polarizations with Dilepton Anisotropies
نویسنده
چکیده
We investigate the production of e+e− pairs from p + Be and nucleus-nucleus collisions from 2 GeV/A to 200 GeV/A within a covariant transport approach and focus on the dilepton angular anisotropies as a function of the dilepton invariant mass. Whereas the low mass regime yields information about the Dalitz decays of the ∆, η and ω, above M ≈0.5 GeV the angular anisotropies provide additional information about the π+π− → ρ0→ e+e− channel in the medium. The anisotropy coefficient is found to change its sign for M > 0.5 GeV in case of nucleus-nucleus reactions when increasing the bombarding energy from 2 GeV/A to 200 GeV/A which sheds some light on the ππ → ρ dynamics. ∗Supported by BMBF and GSI Darmstadt
منابع مشابه
M ay 1 99 6 Preprint UGI - 96 - 11 Submitted to Z . Phys . C Probing Hadronic Polarizations with Dilepton Anisotropies ∗
We investigate the production of e + e − pairs from p + Be and nucleus-nucleus collisions from 2 GeV/A to 200 GeV/A within a covariant transport approach and focus on the dilepton angular anisotropies as a function of the dilepton invariant mass. Whereas the low mass regime yields information about the Dalitz decays of the ∆, η and ω, above M ≈0.5 GeV the angular anisotropies provide additional...
متن کاملRole of the a1 meson in dilepton production from hot hadronic matter.
Dilepton production from hot hadronic matter is studied in an effective chiral Lagrangian with pions, ρ-mesons, and a 1 mesons, We find that the production rates from reactions that involve axial-vector mesons dominate over contributions from all other reactions when the dilepton invariant mass is above 1.5 GeV.
متن کاملDileptons in a coarse-grained transport approach
We calculate dilepton spectra in heavy-ion collisions using a coarse-graining approach to the simulation of the created medium with the UrQMD transport model. This enables the use of dilepton-production rates evaluated in equilibrium quantum-field theory at finite temperatures and chemical potentials. Due to their penetrating nature, the invariant-mass and transverse-momentum spectra of dilepto...
متن کاملDilepton production from resonance scattering in hot hadronic matter.
Dilepton production from resonance scattering in hot hadronic matter is studied. Including the widths of these resonances, which enhance the phase space for dilepton production, we find that the production rate is significantly increased if a resonance appears in the extended phase space. For the reaction π+ρ → l+ l, the finite ρ meson width extends the invariant mass below the ω-meson mass, so...
متن کاملMedium effects in rho-meson photo-production
Medium modifications of hadron properties in hot and/or dense matter are of fundamental interest in connection with the chiral and deconfinement phase transition(s) in QCD. E.g., dilepton spectra measured in high-energy heavy-ion collisions are consistent with a strong broadening of the ρ-meson spectral function in hot and dense hadronic matter [1]. The prevalent medium effects on the ρ are att...
متن کامل