Eur. Phys. J. A (2010) 43: 11-16
https://doi.org/10.1140/epja/i2009-10891-5

Regular Article - Experimental Physics

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

¹ Petersburg Nuclear Physics Institute, 188300, Gatchina, Russia
² Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Bonn, Germany

^* e-mail: nikonov@hiskp.uni-bonn.de

Received: 12 June 2009
Revised: 18 September 2009
Accepted: 15 October 2009
Published online: 10 November 2009

Abstract

A detailed investigation of the reaction np pp has been carried out using the data obtained with the continuous neutron beam produced by charge exchange scattering of protons off the deuterium target. Partial-wave event-by-event analysis based on the maximum likelihood method was applied to determine contributions of different partial waves to the pion production process. A combined analysis of the np pp and pp pp 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 1.8GeV/c . The decay of isoscalar partial waves into the (¹ S ₀)_pp channel provides us with a good tool for the determination of the pp S -wave scalar scattering length in the final state which was found to be a _pp = - 7.5±0.3 fm.