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Institute
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 ´a la Glover / Morgan or Frixione’s cone isolation is employed. Moreover, two different scenarios for charged leptons in the fi state were considered. The fi 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 fl Monte Carlo program. Be- sides the computation of the total cross section this program is also able to generate diff tial 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 7/8 TeV the experimental accuracy for Vγ 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.
The next-to-leading-order electroweak corrections to pp→l\(^{+}\)l\(^{-}\)/ν¯¯¯ν+γ+X production, including all off-shell effects of intermediate Z bosons in the complex-mass scheme, are calculated for LHC energies, revealing the typically expected large corrections of tens of percent in the TeV range. Contributions from quark-photon and photon-photon initial states are taken into account as well, but their impact is found to be moderate or small. Moreover, the known next-to-leading-order QCD corrections are reproduced. In order to separate hard photons from jets, both a quark-to-photon fragmentation function á la Glover/Morgan and Frixione’s cone isolation are employed. The calculation is available in the form of Monte Carlo programs allowing for the evaluation of arbitrary differential cross sections. Predictions for integrated cross sections are presented for the LHC at 7 TeV, 8 TeV, and 14 TeV, and differential distributions are discussed at 14 TeV for bare muons and dressed leptons. Finally, we consider the impact of anomalous ZZγ and Zγγ couplings.