Single-spin Azimuthal Asymmetries in the ``Reduced Twist-3 Approximation''

Abstract

We consider the single-spin azimuthal asymmetries recently measured at the HERMES experiment for charged pions produced in semi-inclusive deep inelastic scattering of leptons off longitudinally polarized protons. Guided by the experimental results and assuming a vanishing twist-2 transverse quark spin distribution in the longitudinally polarized nucleon, denoted as ``reduced twist-3 approximation'', a self-consistent description of the observed single-spin asymmetries is obtained. In addition, predictions are given for the z dependence of the single target-spin asymmetry.

Figures (2)

• Figure 1: The single target-spin asymmetry $A^{\sin\phi_h}_{UL}$ for $\pi^{+}$ production as a function of Bjorken $x$, evaluated using $M_C=0.28$ GeV in Eq.(\ref{['H1T']}). The solid line corresponds to $h_1=g_1$, the dashed one to $h_1=(f_1+g_1)/2$. Data are from Ref. HERM.
• Figure 2: The single target-spin asymmetry $A^{\sin\phi_h}_{UL}$ for $\pi^{+}$ production as a function of $z$ evaluated using $M_C=0.28$ GeV. The solid line corresponds to $h_1=g_1$, the dashed one to $h_1=(f_1+g_1)/2$.