TWIST-4 EFFECTS AND Q(2) DEPENDENCE OF DIFFRACTIVE DIS

In this letter we report the direct perturbative QCD evaluation of twi st-4 effects in diffractive DIS, They are large and have a strong impa ct on the Q(2) dependence of diffractive structure functions at large beta. Based on the AGK rules, we comment on the possible contribution from diffractive higher twists to proportional to 1/Q(2) corrections t o proton structure function at small x. These corrections to the longi tudinal structure function F-L may be particularly large. (C) 1998 Els evier Science B.V.