Nonperturbative QCD corrections to R = σL/ σT

Abstract

The twist-four, spin-two quantum chromodynamic (QCD) corrections have been calculated to the ratio R = σ L / σ T and the Callan-Gross relation for electroproduction on proton and deuteron targets. Using the Wilson operator product expansion (OPE) of the bilocal product of the electromagnetic currents, the coefficient functions were determined using perturbative techniques, neglecting their anomalous dimensions. The MIT bag model was used to evaluate the proton and deuteron matrix elements of the (local) quark operators appearing in the expansion. The corrections to R were found to be small, increasing R by at most a few percent, contrary to a previously reported result which was substantially larger and was based on a quite different approach to estimate higher-twist effects. For completeness the higher-twist corrections to the structure functions W 1, and vW 2, as well as R, in the kinematical region of interest are presented and it is noted these are in agreement with the results implicitly contained in previous independent calculations using similar techniques.