Photon production in heavy-ion collisions close to the pion threshold
Abstract
We report on a measurement of hard photons (Eg>30 MeV) in the reaction Ar+Ca at 180A MeV at an energy in which photons from the decay of pi0 mesons are dominating. Simultaneous measurement with the TAPS spectrometer of the photon spectrum and photon-photon coincidences used for the identification of pi0 enabled the subtraction of pi0 contribution. The resulting photon spectrum exhibits an exponential shape with an inverse slope of E0=(53+-0.03(stat)-5+8(syst)) MeV. The photon multiplicity, equal to (1.21+-0.03(stat)+0.3-0.2(syst))10E0-2, is roughly one order of magnitude larger than the value extrapolated from existing systematics. This enhancement of the hard photon production is attributed to a strong increase in the contribution of secondary np collisions to the total photon yield. We conclude that, on average, the number of np collisions which contribute to the hard photon production is 7 times larger than the number of first chance np collisions in the reaction Ar+Ca at 180A MeV.
Keywords
Cite
@article{arxiv.nucl-ex/9910006,
title = {Photon production in heavy-ion collisions close to the pion threshold},
author = {G. Martinez and L. Aphecetche and Y. Charbonnier and H. Delagrange and D. d'Enterria and T. Matulewicz and Y. Schutz and R. Turrisi and M. Appenheimer and V. Metag and R. Novotny and H. Stroeher and A. R. Wolf and M. Wolf and J. Weiss and R. Averbeck and S. Hlavavc and R. Holzmann and F. Lefevre and R. S. Simon and R. Stratmann and F. Wissmann and M. Hoefman and M. J. van Goethem and H. Loehner and R. W Ostendorf and R. H. Siemssen and P. Vogt and H. W. Wilschut and J. Diaz and A. Marin and A. Kugler and P. Tlusty and V. Wagner and A. Doeppenschmidt},
journal= {arXiv preprint arXiv:nucl-ex/9910006},
year = {2008}
}
Comments
15 pages, 4 figures, references added