Systematics of geometric scaling

Using all available data on the deep-inelastic cross-sections at HERA at x <= 10(-2), we look for geometric scaling of the form or sigma(gamma)*(p) (tau) where the scaling variable tau behaves alternatively like log Q(2) - lambda Y, as in the original definition, or log Q(2) - lambda root Y, which is suggested by the asymptotic properties of the Balitsky-Kovchegov (BK) equation with running QCD coupling constant. A Quality Factor (QF) is defined, quantifying the phenomenological validity of the scaling and the uncertainty on the intercept lambda. Both choices have a good QF, showing that the second choice is as valid as the first one, predicted for fixed coupling constant. A comparison between the QCD asymptotic predictions and data is made and the QF analysis shows that the agreement can be reached, provided going beyond leading logarithmic accuracy for the BK equation. (c) 2007 Published by Elsevier B.V.