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, p+p, d+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 N+N 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 N+N collisions. On the other hand, a direct comparison of the N+N 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.
- Publication:
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Journal of Physics Conference Series
- Pub Date:
- September 2011
- DOI:
- 10.1088/1742-6596/312/1/012008
- arXiv:
- arXiv:1011.5424
- Bibcode:
- 2011JPhCS.312a2008G
- Keywords:
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- Nuclear Experiment
- E-Print:
- 10 pages, 3 figures, proceedings of the International Nuclear Physics Conference - INPC 2010, Vancouver, Canada, July 4 - 9 2010