Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 27: Hadronic Probes III, Particle Production

HK 27.3: Talk

Tuesday, March 17, 1998, 15:00–15:15, C

Subthreshold neutral pion and photon production in proton-nucleus collisions — •L. Aphecetche¹, J.S. Bacelar², H. Delagrange¹, D. d’Enterría¹, M. Hoefman², R. Holzmann³, H. Huisman², N. Kalantar-Nayestanaki², A. Kugler⁴, H. Löhner², G. Martínez¹, J.G. Messchendorp², R.W. Ostendorf², S. Schadmand^2,5, Y. Schutz¹, R.H. Siemssen², P. Tlustý⁴, R. Turrisi^2,1, M.J. van Goethem², M. Volkerts², V. Wagner⁴, and H.W. Wilschut² — ¹GANIL Caen — ²KVI Groningen — ³GSI Darmstadt — ⁴NPI Řež u Prahy — ⁵Univ. Giessen

Deep-subthreshold neutral pion production has been studied in reactions of 190 MeV protons from AGOR with light and heavy targets. Near the absolute threshold energy several mechanisms like nucleon correlations and quantal or dynamical fluctuations may be responsible for particle production. In proton induced reactions we aim to study these processes free from compression effects.

Neutral pions have been measured with the Two-Arm Photon Spectrometer TAPS. Trigger conditions emphasized the detection of the most energetic pions up to the kinematical limit, allowing to study the evolution of pion production mechanisms from elementary NN-collisions to coherent emission. The observed rapidity spectra can not be explained within a nucleon-nucleon collision scheme. Pion energy spectra will be compared to results from dynamical phase-space models. Energetic photon production from secondary pion-nucleon scattering is investigated.