Probing resonance matter with virtual photons

Abstract

In the energy domain of 1-2 GeV per nucleon, HADES has measured rare penetrating probes (e+e-) in C+C, Ar+KCl, d+p, p+p and p+Nb collisions. For the first time the electron pairs were reconstructed from quasi-free n+p sub-reactions by detecting the proton spectator from the deuteron breakup. An experimentally constrained NN reference spectrum was established. Our results demonstrate that the gross features of di-electron spectra in C+C collisions can be explained as a superposition of independent NN collisions. On the other hand, a direct comparison of the NN reference spectrum with the e+e- invariant mass distribution measured in the heavier system Ar+KCl at 1.76 GeV/u shows an excess yield above the reference, which we attribute to radiation from resonance matter. Moreover, the combined measurement of di-electrons and strangeness in Ar+KCl collisions has provided further intriguing results which are also discussed.

10 pages, 3 figures, proceedings of the International Nuclear Physics Conference - INPC 2010, Vancouver, Canada, July 4 - 9 2010

References in corpus (12)

• Hadron Production in Ultra-relativistic Nuclear Collisions: Quarkyonic Matter and a Triple Point in the Phase Diagram of QCD
• Phi decay: a relevant source for K- production at SIS energies?
• Deep sub-threshold ${\Xi }^{-}$ production in Ar+KCl reactions at 1.76A GeV
• Dilepton production and off-shell transport dynamics at SIS energies
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• Modification of the $\omega$-Meson Lifetime in Nuclear Matter
• Origin of the low-mass electron pair excess in light nucleus-nucleus collisions
• Study of dielectron production in C+C collisions at 1 AGeV
• A versatile method for simulating pp -> ppe+e- and dp -> pne+e-p_spec reactions
• Dilepton production in proton-proton and quasifree proton-neutron reactions at 1.25 GeV
• Role of phi decays for K- yields in relativistic heavy-ion collisions
• Inclusive Dielectron Production in Ar+KCl Collisions at 1.76 AGeV studied with HADES