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.

Figures (7)

• Figure 1: Collinear twist-3 factorization setup: 2-parton fragmentation, left:$n=0$ unobserved partons in the final state, right:$n=1$ unobserved gluon in the final state.
• Figure 2: Collinear twist-3 factorization setup: dynamical quark-gluon-quark fragmentation, left:$n=0$ unobserved partons in the final state, right:$n=1$ unobserved gluon in the final state.
• Figure 3: Collinear twist-3 factorization setup: dynamical quark-quark-gluon fragmentation.
• Figure 4: Virtual graphs contributing to dynamical twist-3 $qg$ fragmentation.
• Figure 5: Real graphs contributing to dynamical twist-3 $qg$ and $\bar{q}q$ fragmentation.