Polarization asymmetry in high-p⊥inclusive production

Abstract

We calculate the asymmetry A/sub L/L for scattering of longitudinally polarized protons from a polarized target in an effort to discriminate among constituent models of inclusive high-transverse-momentum hadron and jet production. A/sub L/L is defined by A/sub L/L = (Edsigma/sup +//sub L//d/sup 3/p - Edsigma/sup -//sub L//d/sup 3/p) /(Edsigma/sup +//sub L//d/sup 3/p + Edsigma/sup -//sub L//d/sup 3/p), where sigma/sup +//sub L/ (sigma/sup -//sub L/) is the pp cross section for the configuration in which the proton helicities are the same (opposite). For inclusive pion production the principal mechanism in the constituent-interchange model is quark-meson scattering, which leads to the prediction A/sub L/L = 0. However, in several recent models the mechanism for producing high-transverse-momentum pions invloves processes such as quark-quark scattering for which it is expected that A/sub L/L not = 0. In the present paper A/sub L/L is calculated for inclusive production of pions and jets in the phenomenological effective-gluon model and also in a model based on quantum chromodynamics. Among the important ingredients of such calculations are the distribution functions for quarks in a polarized proton. A new model of these is developed and compared to the most recent SLAC data. It is shown that even in modelsmore » where A/sub L/L not = 0, the magnitude and sign of A/sub L/L depend sensitively on the strong-interaction dynamics and hence can be used to discriminate among models of inclusive production.« less