QCD and Electroweak NLO Corrections to W + Photon and Z + Photon Production Including Leptonic Decays

Abstract

At a hadron collider as the LHC or the Tevatron the production of a photon in association with a leptonically decaying vector boson represents an important class of processes. These processes stand out due to a very clean signal of a photon and two leptons. Furthermore they provide direct access to the photon{vector-boson couplings and thus an easy opportunity to test the gauge sector of the Standard Model. Within the scope of this work we present a full calculation of the next-to-leading-order corrections which include the O(αs) corrections of the strong interaction as well as the electroweak corrections of O(α) including all photon-induced contributions. For the creation of matrix elements we use methods based on Feynman diagrams. The IR singularities are treated with the dipole subtraction technique. In order to separate photons from jets, a quark-to-photon fragmentation function á la Glover / Morgan or Frixione's cone isolation is employed. Moreover, two different scenarios for charged leptons in the final state were considered. The first scenario for dressed leptons assumes that a charged lepton and a photon will be recombined if they are collinear. In the second scenario for bare muons it is assumed that leptons and photon can be separated in a detector also if they are collinear. For our calculation we implemented all corrections into a exible Monte Carlo program. Besides the computation of the total cross section this program is also able to generate differential distributions of several experimentally motivated observables. Apart from the expected large electroweak corrections in the high transverse-momentum regions and sizeable corrections in the resonance regions of the transverse or the invariant masses we found photon-induced corrections up to several 10% for high transverse momenta. Within run I at the LHC for 7=8TeV the experimental accuracy for V production was roughly 10%. Due to the higher luminosity at run II this accuracy will be reduced to the level of a few percent so that corrections of the same order within the theoretical predictions might become relevant. In this work we present results for the total cross section at the LHC for 7, 8 and 14 TeV and the corresponding distributions for 14 TeV