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

TL;DR

This paper investigates negative pion production in neutron-proton collisions below 1.8 GeV/c using partial wave analysis to identify contributions of different partial waves and determine the pp S-wave scattering length.

Contribution

It introduces a combined analysis of np and pp pion production data to quantify isoscalar partial wave contributions and measure the pp S-wave scattering length.

Findings

Determined the pp S-wave scattering length as a_{pp}=-7.5±0.3 fm.

Identified isoscalar partial wave contributions in the energy range 1.1 to 1.8 GeV/c.

Applied partial wave analysis to neutron-proton collision data.

Abstract

A detailed investigation of the reaction np -> pp\pi^{-} 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 -> pp\pi^{-} and pp -> pp\pi^{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 (^1S_0)_{pp}\pi$ 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 a_{pp}=-7.5\pm 0.3 fm.