Resummation for Polarized Semi-Inclusive Deep-Inelastic Scattering at   Small Transverse Momentum
  We study the transverse-momentum distribution of hadrons produced in semi-inclusive deep-inelastic scattering (SIDIS). We consider cross sections for various combinations of polarizations of the initial lepton and nucleon or the produced hadron, for which we perform the resummation of large double-logarithmic perturbative corrections arising at small transverse momentum. We present phenomenological results for the processes $lp\to l\pi X$ with longitudinally polarized leptons and protons. We discuss the impact of the perturbative resummation and of estimated non-perturbative contributions on the corresponding cross sections and their spin asymmetry. Our results should be relevant for ongoing studies in the COMPASS experiment at CERN, and for future experiments at the proposed eRHIC collider at BNL. 
Yuji Koike, Junji Nagashima (Niigata Univ.) and Werner Vogelsang (BNL   and RBRC)