Confinement and scaling in deep inelastic processes

Abstract

We show that parton confinement in the final state generates large $1/Q^2$ (higher twist) corrections to Bjorken scaling. For treatment of these non-perturbative effects, we derive a new expansion in powers of $1/Q^2$ for the structure function that is free of infra-red singularities and which reduces corrections to the leading term. The leading term represents scattering from an off-mass-shell parton, which keeps the same virtual mass in the final state. This term appears as a function of a new variable $\bar x(x,Q^2)$, which coincides with the Bjorken variable x for $Q^2\to\infty$. Analysis of the data shows excellent scaling at large x, where power corrections are dominant. The approach accommodates also the QCD logarithmic corrections and the behavior of the structure functions is well reproduced within a wide kinematical range. Since the new scaling variable $\bar x(x,Q^2)$ incorporates the higher twist effects, it allows us to extract the ratio $F_2^n(x)/F_2^p(x)$ for $x\to 1$ from the available data at moderate Q^2.