Fragmentation contributions to transverse nucleon spin observables in semi-inclusive deep-inelastic scattering at NLO

Abstract

We study the spin-dependent cross section in semi-inclusive deep-inelastic lepton-nucleon collisions, $\ell +N^{\uparrow }\to \ell +h+X$. We focus on the cross section that is integrated over the transverse momentum $P_{h\perp }$ of the detected unpolarized hadron. We analyze this cross section at large virtuality $Q^2$ of the exchanged virtual photon within the framework of collinear twist-3 factorization in perturbative QCD. The two main transverse spin observables, the single nucleon spin asymmetry (SSA) and the double longitudinal lepton-transverse nucleon spin asymmetry (DSA), both receive contributions from chiral-odd twist-3 three-parton fragmentation functions. We study these fragmentation contributions to Next-To-Leading Order (NLO) in perturbative QCD. We explicitly observe that collinear twist-3 factorization holds for these contributions at the one-loop level. We confront our NLO formulae with HERMES data and provide numerical predictions for EIC kinematics.

Comments: 30 pages, 7 figures, minor changes, appendix added. Final version published in Phys Rev D