Resummation of double collinear logs in BK evolution versus HERA data

We present a global fit to HERA data on the reduced cross section measured in electron proton collisions in the region of small Bjorken-x: x <= x(0) = 10(-2) and moderate to high values of the virtuality Q(2) < Q(max)(2) = 650 GeV2. The main dynamical ingredients in the fits are two recently proposed improved BK equations for the description of the small-x evolution of the dipole scattering amplitude [1,2]. These two new equations provide an all-order resummation of double collinear logarithms that arise beyond leading logarithmic accuracy. We show that a very good description of data is possible in both cases, provided the parent dipole or smallest dipole prescriptions are employed for the running of the coupling. (C) 2016 Elsevier B.V. All rights reserved.