Backward nucleon production by heavy baryonic resonances in proton-nucleus collisions

Abstract

The production of backward nucleons, N (180 • ), at 180 • in the nuclear target rest frame in protonnucleus (p + A) collisions is studied. The backward nucleons appearing outside of the kinematically allowed range of proton-nucleon (p + N ) reactions are shown to be due to secondary reactions of heavy baryonic resonances produced inside the nucleus. Baryonic resonances R created in primary p + N reactions can change their masses and momenta due to successive collisions R + N → R + N with other nuclear nucleons. Two distinct mechanisms and kinematic restrictions are studied: the reaction R + N → N (180 • ) + N and the resonance decay R → N (180 • ) + π. Simulations of p + A collisions using the Ultra-relativistic Quantum Molecular Dynamics model support these mechanisms and are consistent with available data on proton backward production.

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“…However, the multistep processes in similar reactions may probe the cumulative phenomenon of subthreshold particle production [43]. This has been confirmed by microscopic transport calculations [44,45] and is still to be verified experimentally.…”