14 research outputs found
Toy Model for Pion Production II: The role of three-particle singularities
The influence of three-particle breakup singularities on s-wave meson
production in nucleon-nucleon collisions is studied within the distorted wave
Born approximation. This study is based on a simple scalar model for the
two-nucleon interaction and the production mechanism. An algorithm for the
exact numerical treatment of the inherent three-body cuts, together with its
straightforward implementation is presented. It is also shown that two
often-used approximations to avoid the calculation of the three-body breakup
are not justified. The possible impact on pion production observables is
discussed.Comment: 14 pages, 6 figure
Towards a field theoretic understanding of NN->NNpi
We study the production amplitude for the reaction NN->NNpi up to
next--to--leading order in chiral perturbation theory using a counting scheme
that takes into account the large scale introduced by the initial momentum. In
particular we investigate a subtlety that arises once the leading loop
contributions are convoluted with the NN wavefunctions as demanded by the
non--perturbative nature of the NN interaction. We show how to properly
identify the irreducible contribution of loop diagrams in such type of
reaction. The net effect of the inclusion of all next-to-leading order loops is
to enhance the leading rescattering amplitude by a factor of 4/3, bringing its
contribution to the cross section for pp->dpi+ close to the experimental value.Comment: 15 Pages, 5 Figure