Transverse momentum dependence of the quark helicity distributions and the Cahn effect in double-spin asymmetry $A_{LL}$ in Semi Inclusive DIS

• Main Authors: Anselmino, M, Efremov, A, Kotzinian, A, Parsamyan, B
• Format: Journal Article
• Language: English
• Published: 04-08-2006
• Subjects: Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.hep-ph/0608048

Phys.Rev.D74:074015,2006 Within the LO QCD parton model of Semi Inclusive Deep Inelastic Scattering,
$\ell N \to \ell h X$, with unintegrated quark distribution and fragmentation
functions, we study the $\bfP_{hT}$ dependence of the double longitudinal-spin
asymmetry $A_{LL}$. We include 1/Q kinematic corrections, which induce an
azimuthal modulation of the asymmetry, analogous to the Cahn effect in
unpolarized SIDIS. We show that a study of $A_{LL}$ and of the weighted DSA
$A_{LL}^{\cos\phi_h}$ allows to extract the transverse momentum dependence of
the unintegrated helicity distribution function $g_{1L}^q(x,k_\perp)$ [or
$\Delta q(x, k_\perp)]$. Predictions, based on some models for the unknown
functions, are given for ongoing COMPASS, HERMES and JLab experiments.