Inelastic Reactions Induced By Pions On He-4 At 68, 120, 135, 156, 174 and 208 Mev

Total and differential cross sections for the pi(+) He-4 ->p(+) p H-3, pi(+) He-4 -> pi(+)2p2n and pi(+) He-4 -> 3pn reactions have been measured at E(pi) = 68, 120, 135 and 156 MeV. Total and differential cross-sections for the pi(-) He-4 -> pi(-) p h-3 and pi(-) He-4 -> pi(-)2p2n reactions have also been measured at E(pi) = 120, 135, 156, 174 and 208 MeV. The measurements have been performed using high-pressure helium-filled streamer chamber, exposed to the synchrocyclotron of the JINR of Dubna. The analysis of the (pi p H-3) reactions shows that the proton knock-out process is mainly a quasi-free (pi p) scattering involving the Delta(1232)-resonance excitation. The same resonance also seems to be produced in the (pi2p2n) reaction. The pi(+) absorption reaction takes place on a nucleon pair and the cross-section values turn out to be close to those of the pi(+) d -> pp reaction.