The study of the negative pion production in neutron-proton collisions at beam momenta below 1.8 GeV/c

Abstract

A detailed investigation of the reaction np → ppπ − has been carried out using the data obtained with the continuous neutron beam produced by charge exchange scattering of protons off a deuterium target. A partial wave event-by-event based maximum likelihood analysis was applied to determine contributions of different partial waves to the pion production process. The combined analysis of the np → ppπ − and pp → ppπ 0 data measured in the same energy region allows us to determine the contribution of isoscalar partial waves (I=0) in the momentum range from 1.1 up to 1.8 GeV/c. The decay of isoscalar partial waves into ( 1 S0)ppπ channel provides a good tool for a determination of the pp S-wave scalar scattering length in the final state which was found to be app = −7.5 ± 0.3 fm.PACS. 13.75.Cs Nucleon-nucleon interactions -13.85.Lg Total cross sections -25.40.Fq Inelastic neutron scattering

Analysis of pion production data measured by HADES in proton-proton collisions at 1.25 GeV

“…This peak is created due to a compromise between decreasing partial wave amplitudes and three-body phase volume which grows rapidly near the pion production threshold. A similar behavior was observed in the isospin I = 0 sector [48]. It would be interesting to check whether such phenomenon can explain a resonance-like behavior of the pn → dπ + π − total cross cross section observed in [49].…”

Analysis of pion production data measured by HADES in proton-proton collisions at 1.25 GeV

“…This peak is created due to a compromise between decreasing partial wave amplitudes and three-body phase volume which grows rapidly near the pion production threshold. A similar behavior was observed in the isospin I = 0 sector [44]. It would be interesting to check whether such phenomenon can explain a resonance-like behavior of the pn → dπ + π − total cross cross section observed in [45].…”