Accurate QCD predictions for new variables to study dilepton transverse   momentum
  We report on the computation of the angle-between-leptons distribution in Drell-Yan processes. More precisely we study the recently introduced variable phi*, which provides us with a more accurate probe of the low Q_T domain of Z boson production at hadron colliders. Our theoretical prediction is obtained by matching a next-to-next-to leading logarithmic (NNLL) resummation to a fixed order calculation at next-to-leading order (NLO). We find that the result significantly differs from a pure fixed order calculation in a wide range of the observable we are interested in, clearly indicating the need for resummation. We also perform a first comparison to the measurement by the D0 collaboration, finding good agreement between theory and experiment. 
Simone Marzani, Andrea Banfi, Mrinal Dasgupta and Lee Tomlinson
hep-ph