Group Theoretical Analysis of Light-Cone Dominated Hadronic Processes and Twist Decomposition of Nonlocal Operators in Quantum Chromodynamics

Abstract

In the framework of nonlocal light-cone expansion of two current operators we construct bilocal as well as trilocal QCD light-cone operators with definite geometric twist. We are able to decompose uniquely the appearing QCD light-cone operators into all their twist parts on the light-cone. The quark distribution functions and the vector meson distribution amplitudes which are defined as forward and skewed nucleonic matrix elements of nonlocal light-cone operators are classified with respect to geometric twist. Hereby we found well-kown and new Wandzura-Wilczek type relations between the quark distribution functions with dynamical twist and, additionally, between the vector meson distribution amplitudes with dynamical twist. Using group theoretical methods we are able to construct all bilocal off-cone QCD operators with twist 2 and 3. Additionally, we calculate their nucleonic matrix elements (double distribution functions, scalar and vector meson distribution amplitudes). In some special cases we give also the twist decomposition of off-cone QCD operators from minimal up to infinite twist.