A QCD description of the ATLAS jet veto measurement

We present a new QCD description of the ATLAS jet veto measurement, using the Banfi-Marchesini-Smye equation to constrain the interjet QCD radiation. This equation resums emissions of soft gluons at large angles, at leading-logarithmic accuracy, and accounts for both the so-called Sudakov and nonglobal logarithms. We show that this approach is able to reproduce, with no fitting parameters, the fraction of high-p_T forward-backward dijet events which do not contain additional hard emissions in the interjet rapidity range. We also compute the gap fraction in fixed-order perturbation theory to O(αs2) and show that the perturbative series is unstable at large rapidity intervals.