Production of low transverse momentum particles in high energy meson-proton single particle inclusive scattering

The production of low transverse momentum particles in the fragmentation region of the pion in high energy pion-proton collisions is studied. Phenomenological models are developed using triple Regge theory and the quark recombination model, and calculations are made to predict single particle inclusive cross sections. A triple Regge description of the reactions π+- p → π+- x in the region x approximately >= 0.8, where x is the momentum x fraction variable, is obtained by extending factorization to t (momentum transfer) not equal to 0 and by using factorizable Regge amplitudes and a well established triple Regge description of pp → px. This provides a parameterization of the pion triple Regge coupling functions, which is used to compute the inclusive cross section. The total inelastic diffractive cross section is also computed and shown to account for most of the rise with energy of the total experimental cross section for σsub(TOT)sup(π+p) and σsub(TOT)sup(π-p). Predictions are made for the KN system, both for the inclusive cross section and the total inelastic diffractive cross section. The quark recombination model is formulated to describe the reactions π+p → p+-x in the region 0.3 approximately <x approximately <= 0.9. A distinctive structure in the experimental distributions is reproduced in a simple self-consistent model that is sensitive to the parameterization of the pion sea. The dimensional counting rule prediction for the pion valence quark structure is supported by the results. Predictions for the reactions π-p → p+-x are discussed. In the region 0.75 approximately <= x approximately <= 0.90 an overlap between the triple Regge and quark-parton approaches occurs through the high energy kinematic relation x = 1-M2/s. A calculation for the reaction π+p → p-x supports the proposal that these two reaction mechanisms contribute additively in this region