Peripheral anti pn production and decay angular distributions in the reaction π-p → (anti pn)p at 12 GeV/c incident momentum

The reaction π-p → (anti pn)psub(s) where psub(s) is a slow proton, was measured at 12 GeV/c incident momentum with the CERN-OMEGA spectrometer. Both antiproton and proton were identified uniquely by electronics information. The authors obtained 1844 events with four-momentum transfer squared in the range 0.13 <= mod(t) <= 0.33 GeV2 and with invariant masses M(anti pn) up to 2.5 GeV. The corresponding cross section in this t range is determined to be sigma = 4+0.4 μb. Extrapolating the differential cross section over the whole t range assuming dsigma/dt approximately exp(5.3t) a cross section of sigma = 9.3+-2.0 μb is estimated. Comparison with data on π-p → (anti pp)nsub(s) (where nsub(s) is a slow neutron) in the same t range shows that the (anti pn)psub(s) and (anti pp)nsub(s) cross sections have approximately the same magnitude. (Auth.)