Azimuthal decorrelations and jet vetoes in dijet events

Studies of azimuthal decorrelation of dijets with a jet veto with the ATLAS detector Measurements of di-jet systems with a veto on additional jets, probe QCD radiation effects. The two jets in each event with the highest transverse momentum are taken as the dijet system and a rapidity interval is defined as the region in rapidity between the centroids of these two jets. The fraction of dijet events without an additional jet in this rapidity interval and the mean jet multiplicity in the interval are presented as a function of the mean transverse momentum of the dijets and of the rapidity interval size. Correlations between the azimuthal angles of the dijets are studied both with and without a veto on additional jet activity in the rapidity interval between the jets. This study probes different approaches to the resummation of large logarithms when performing QCD calculations.