Deep-subthreshold eta and pi0 production probing pion dynamics in the reaction Ar + Ca at 180-A-MeV.

Martinez, G. ; Charbonnier, Y. ; Aphecetche, L. ; et al.
Phys.Rev.Lett. 83 (1999) 1538-1541, 1999.
Inspire Record 508818 DOI 10.17182/hepdata.19447

We report on a measurement of subthreshold η and π0 mesons in the reaction Ar+Ca at 180A MeV. We find that the ratio of the η to π0 meson-production cross section is more than a factor of 20 smaller than the one expected from threshold-energy scaling of meson production. In addition, the multiplicity of high mt π0 increases faster with the centrality of the reaction than the multiplicity of the bulk of π0 mesons. This behavior is explained by the rescattering of π mesons in nuclear matter at the origin of most energetic particles.

2 data tables

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Multistep production of eta and hard pi0 mesons in subthreshold Au Au collisions.

Wolf, A.R. ; Appenheimer, M. ; Averbeck, R. ; et al.
Phys.Rev.Lett. 80 (1998) 5281-5284, 1998.
Inspire Record 471975 DOI 10.17182/hepdata.41989

The neutral π0 and η mesons are studied in 197Au−197Au collisions at an incident energy of 800AMeV, substantially below the threshold for η production in N−N collisions. While the gross π0 multiplicity increases almost linearly with the number of participant nucleons, the multiplicities of η and hard π0 mesons show a stronger than linear dependence. The nonlinearity is governed by the average transverse-mass excess 〈mt〉−(s−2mN) of the mesons and is insensitive to their final-state interaction in the nuclear medium.

4 data tables

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