We develop a general approach to the evolution equations fot higher-twist parton distributions. A complete set of two-particle renormalization group kernels is derived that serve as building blocks in arbitrary QCD evolution equations to twist-four accuracy. It is shown that the $2to 2$ evolution kernels that involve “non-partonic” components of field operators, and, most remarkably, also $2to3$ splitting kernels do not require independent calculation and can be restored from the known leading-twist results using conformal symmetry and Lorentz transformations. The kernels are presented for the renormalization of light-ray operators built of chiral fields in a particular basis such that the conformal symmetry is manifest. The results can easily be recast in momentum space, in the form of evolution equations for generalized parton distributions.

University of Regensburg