Pion production in NN collisions - art. no. 011001

The recently proposed irreducible tensor formalism for hadron scattering an d reactions is extended to pion production in NN collisions and a form akin to that of Wolfenstein for elastic NN scattering is derived together with exact partial wave expansions for the amplitudes. Explicit formulas are der ived for spin observables relevant to differential as well as total cross s ection measurements employing a polarized beam on a polarized target which are currently of experimental interest.