? Production in proton-nucleus reactions

Abstract

The production of q-mesons in proton-nucleus reactions is analysed with respect to primary nucleon-nucleon (NN~NNq) and secondary pion-nucleon (nN~qN) production processes on the basis of Hartree-Fock groundstate momentum distributions and free on-shell production processes. The folding model adopted compares well for meson production with more involved simulations based on VUU transport equations. Similar to K § production in proton-nucleus reactions the q-mesons are primarily produced by the ~z N--* q N channel. However, q-mesons are absorbed in nuclei via excitation of the N* (1535) resonance which leads to strong distortions of the primordial spectra. On the other hand, the experimental mass dependence of the differential cross sections might yield information about the in-medium properties of this resonance.

K?-meson production in proton-nucleus collisions

“…A justification of the folding model and a comparison with experimental data can be found in the publications of Cassing et al [27], Sibirtsev [28] and references therein. The model reasonably reproduces available experimental results on 77 and K + production in pA collisions.…”

“…All obtained c~ values are then (27) obtained by Barton et al [47] in an analysis of the A dependence of p, 1r +, ~T-, K +, K-and ~ production in pA collisions at an incident proton energy of 100 GeV is drawn as a solid line. From the remarkable agreement between the various results shown in Fig.…”

Subthreshold inclusiveη production in nuclei by 1 GeV protons

“…The data are corrected for the apparatus dead time, 7 conversion probability in the target and in the polyethylene plates, efficiencies of converters and Cherenkov counters 9 The cross-sections could be underestimated due to events in which an q is produced in coincidence with a charged particle (p or ~z +) that hits one of the anticoincidences. The data are analyzed in the frame of a simple folding model for proton induced inclusive meson production on nuclei developed by Cassing et al [9]. The model successfully reproduces the subthreshold (p, K +) total cross section data [18], where the effect of the meson reabsorption in the nucleus is negligible 9 In this model two free on shell elementary q production mechanisms are taken into account: the direct one pN~pNq and the two-steps process pN~NN~, rcN~tiN.…”

“…Information can however be inferred from the study of inclusive q production on nuclei. In fact, as pointed out in several papers [6][7][8][9], the final state interaction of the q meson with the nucleons strongly influences both the q energy spectrum and the mass number dependence of the inclusive cross section, which are therefore sensitive to the features of the tlN interaction.…”

Fermi Motion and Nuclear Modification Factor

“…of the order of the nuclear Fermi momentum. At intermediate energies the inclusion of momentum distributions in nuclei quantifying the nucleon motion is crucial for the production of kaons [15,19,17], eta mesons [18] and antiprotons [16] in p+A collisions. It is well known that at subthreshold and near-to-threshold collisions the Fermi motion leads to a huge enhancement of hadron production cross sections based on the first collision model.…”