PoS - Proceedings of Science
Volume 308 - QCD Evolution 2017 (QCDEV2017) - Thursday, May 25, 2017- Morning 1
Generalized Wandzura Wilczek Relations and Orbital Angular Momentum
S. Liuti*, M. Engelhardt and A. Rajan
Full text: pdf
Published on: March 23, 2018
New Lorentz Invariance Relations (LIRs) were presented between twist-three Generalized Parton Distributions (GPDs) and transverse momentum, $k_T$, moments of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs). By implementing both these LIRs and the QCD Equations of Motion in the quark quark correlation function, we generated a new series of Wandzura Wilczek (WW) relations in the off-forward sector. Two of these WW relations take on a particularly interesting physical meaning in that they provide a clear interpretation of the QCD structure of Orbital Angular Momentum (OAM) in the nucleon. In particular, they provide a solution to the outstanding puzzle of how OAM could be simultaneously described by twist-two GTMDs and twist-three GPDs.
Additional relations were discussed, in particular, for the helicity configurations that can be detected analyzing specific spin asymmetries: one corresponding to a longitudinally polarized quark in an unpolarized proton, associated with spin-orbit correlations, and one for transverse proton polarization, as a generalization of the relation obeyed by the $g_2$ structure function; finally, we defined a relation connecting the off-forward extension of the Sivers function to an off-forward Qiu-Sterman term.
DOI: https://doi.org/10.22323/1.308.0041
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