Multi-nucleon pion absorption in the 4He(π+,ppp)n reaction

Abstract Three-proton emission cross sections for the 4 HE(π + , ppp)n reaction were measured at T π + = 165 MeV over a wide angular range in a kinematically complete experiment. The momentum distribution of the undetected neutron and angular correlations have been compared with three- and four-body phase space Monte Carlo calculations. The results indicate that most of the three-proton coincidences result from three nucleon absorption. The total three-nucleon absorption cross section is estimated to be σ 3N =4.5±1.0 mb from phase-space integration. This cross section does not account for the discrepancy between total absorption cross sections and two-nucleon absorption cross sections.