Geometric scaling above the saturation scale

We show that the evolution equations in QCD predict geometric scaling for quark and gluon distribution functions in a large kinematical window, which extends above the saturation scale up to momenta Q(2) of order 100 GeV2. For Q(2) < Q(s)(2), with Qs the saturation momentum, this is the scaling predicted by the Colour Glass Condensate and by phenomenological saturation models. For 1 less than or similar to ln(Q(2)/Qs(2)) much less than ln(Q(s)(2)/A(QCD)(2)), we show that the solution to the BFKL equation shows approximate scaling, with the scale set by Qs. At larger Q2, this solution does not scale any longer. We argue that for the intermediate values of Q2 where we find scaling, the BFKL rather than the double logarithmic approximation to the DGLAP equation properly describes the dynamics. We consider both fixed and running couplings, with the scale for running set by the saturation momentum. The anomalous dimension which characterizes the approach of the gluon distribution function towards saturation is found to be close to, but lower than, one half. (C) 2002 Elsevier Science B.V. All rights reserved.