Mass corrections in deep-inelastic scattering

The moment sum rules for deep-inelastic lepton scattering are expected for asymptotically free field theories to display a characteristic pattern of logarithmic departures from scaling at large enough Q2. In the large-Q2 limit these patterns do not depend on hadron or quark masses m. For modest values of Q2 one expects corrections at the level of powers of m2Q2. We discuss the question whether these mass effects are accessible in perturbation theory, as applied to the twist-2 Wilson coefficients and more generally. Our conclusion is that some part of the mass effects must arise from a nonperturbative origin. We also discuss the corrections which arise from higher orders in perturbation theory for very large Q2, where mass effects can perhaps be ignored. The emphasis here is on a characterization of the Q2, x domain where higher-order corrections are likely to be unimportant.