pi(+/- 4)-He interactions at 218 MeV/c

This paper presents the results of a study on pion-helium interaction channels with two charged secondaries at 106 MeV by means of a visualizing technique based on a Self-Shunted Streamer Chamber (SSSC). Following previous studies at several energies, the present work is intended to cover the lack of data for energies below the Delta(1232) threshold in 4 He, and to reveal new phenomenology far from the A activation. Relative branching ratios for different channels are given; as well as new evidence for single charge exchange reaction and for clustering effects between neutron and He-3 in the neutron knockout reaction. First evidence for the existence of a single-gamma emission channel is presented. Comparison of the differential cross-sections, deduced from the elastic and single-gamma emission events, with the elastic cross-sections obtained in previous measurements is performed. The energy distributions of the emitted single gammas are also presented; fits with Planck's radiation distribution give good chi(2) revealing possible nucleus' black-body-like behaviour.The black-body temperature for He-4 nucleus in the aforementioned conditions is extracted.