This project proposes series of experiments studying dielectron production in proton and pion induced reactions by means of the new spectrometer HADES and proton/pion beam facilities at the GSI. The new pion facility at GSI will be used for the first time to provide intensive pion beams with beam momentum of 0.8 and 1.3GeV/c for the dilepton production.
The main goal of the project is to study dilepton production in elementary proton-proton and pion-proton collisions at energies near production thresholds for the light vector mesons (rho/omega). This is very important for the understanding of the vector meson-nucleon interactions, the Vector Dominance Model of hadron-photon couplings and for various processes contributing to dilepton production in heavy ion collisions at SIS bombarding energies (i.e. 1 to 2 AGeV).
In the frame of this project two types of experiments are proposed:
- Studies of the dielectron spectra from pp interactions at proton beam energies of 2 and 4.0GeV. These experiments will allow determining basic contributions to the dielectron production at and above the rho/omega meson production threshold. In particular the Dalitz dielectron decays of the eta meson and the Delta resonance can be investigated with better precision. The vector meson production amplitudes will be studied at and above the production threshold.
- Investigation of pi-p ->(rho/omega) n->e+e-n reaction below and above the production threshold for the omega meson will be used to study coupling of the vector mesons to the low lying baryonic resonances and the rho/omega interference effect.
The study of dilepton production in elementary pp and pion-p collisions above the omega production threshold has also very important instrumental reasons because it will prove both acceptance and efficiency corrections of the spectrometer and will demonstrate the excellent invariant mass resolution of the spectrometer. These studies are important prerequisites for the planned investigations of proton-nucleus and pion-nucleus reactions searching for in-medium vector meson modifications.