Inelastic reactions induced by pions on 4 He at 68, 120, 135, 156, 174 and 208 MeV

Summary  Total and differential cross sections for the π+ 4He→π+p3H, π+ 4He → π+2p2n and π+ 4He → 3pn reactions have been measured atE π =68, 120, 135 and 156 MeV. Total and differential cross-sections for the π− 4He → π−p3H and π− 4He → π−2p2n reactions have also been measured atE π =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 (πp3H) reactions shows that the proton knock-out process is mainly a quasi-free (πp) scattering involving the Δ(1232)-resonance excitation. The same resonance also seems to be produced in the (π2p2n) reaction. The π+ absorption reaction takes place on a nucleon pair and the cross-section values turn out to be close to those of the π+d → pp reaction.