Subthreshold pion dynamics as a source for hard photons beyond proton-neutron bremsstrahlung in heavy in heavy-ion collisions

K.K. Gudima (1) , T. Matulewicz (1) , H. Delagrange (1, 2) , F.M. Marqués (3) , Gines Martinez Garcia (1, 2) , R.W. Ostendorf (1) , M. Ploszajczak (1) , Y. Schutz (1, 2) , V.D. Toneev (1) , P. Bozek (1) , S. Hlavac (4) , R. Holzmann (4) , A. Schubert (4) , V. Wagner (4) , H. Lohner (5) , J.H.G. van Pol (5) , R.H. Siemssen (5) , H.W. Wilschut (5) , Joseph Diaz (6) , A. Marin (6)

1 GANIL - Grand Accélérateur National d'Ions Lourds
2 SUBATECH - Laboratoire SUBATECH Nantes
3 LPCC - Laboratoire de physique corpusculaire de Caen
4 GSI - Gesellschaft für Schwerionenforschung
5 KVI - Kernfysisch Versneller Instituut
6 IFIC - Instituto de Fisica Corpuscular

We report on the first measurement in heavy-ion collisions of hard photons of extremely high energies that extend the photon spectrum to 5 times the beam energy per nucleon. The photon spectrum was measured for the systems 86Kr+natNi at 60AMeV and 181Ta+197Au at 40A MeV. The data are interpreted using the Dubna cascade model. The radiative channel of pion-nucleon interaction π+N→N+γ, involving subthreshold pions produced in the nuclear medium, dominates all other processes considered for the production of the very energetic photons. This channel was never considered so far at beam energies below the pion threshold.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

K.K. Gudima, T. Matulewicz, H. Delagrange, F.M. Marqués, Gines Martinez Garcia, et al.. Subthreshold pion dynamics as a source for hard photons beyond proton-neutron bremsstrahlung in heavy in heavy-ion collisions. Physical Review Letters, 1996, 76, pp.2412-2415. ⟨10.1103/PhysRevLett.76.2412⟩. ⟨in2p3-00016126⟩