Multi-proton emission in Δ region in charge-exchange reactions

Energy spectra of the forward going ejectile, detected in coincidence with two and three protons in (p, n) and (3He, t) reactions, have been calculated for a 12C target nucleus. We picture the incoming projectile emitting a beam of virtual pions, which subsequently gets absorbed by the target nucleus. Using a pseudovector pion coupling and the eikonally distorted beam and the ejectile, the cross section is written in terms of the absorption cross section of pions in the nucleus. We approximate this cross section by the measured (π+, 2p) and (π+, 3p) absorption cross sections for a real pion. The calculated spectral shapes agree well with the measured ones.