Jet cross sections in polarized photon–hadron collisions

We present a computation of one- and two-jet cross sections in polarized photon–hadron collisions, which is accurate to next-to-leading order in QCD. Our results can be used to compute photoproduction cross sections in electron–proton scattering. To this purpose, we investigate the structure of the polarized Weizsäcker–Williams function, where we include a universal, non-logarithmic term, neglected in the literature. We construct a Monte Carlo code, within the framework of the subtraction method, and we use it to study the phenomenology of jet production in the energy range relevant to HERA. In particular, we investigate the perturbative stability of our results, and we discuss the possibility of constraining polarized parton densities of the proton and the photon using jet data.