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The investigation of weak bosons $V$ ($V=mathrm{W}^{pm}$, $mathrm{Z}$) produced with or without associated hard QCD jets will be of great phenomenological interest at the LHC. Owing to the large cross sections and the clean decay signatures of the vector bosons, weak-boson production can be used to monitor and calibrate the luminosity of the collider, to constrain the PDFs, or to calibrate the detector. Moreover, the $Z$+jet(s) final state constitutes an important background to a large variety of signatures of physics beyond the Standard Model. To match the excellent experimental accuracy that is expected at the LHC, we have worked out a theoretical next-to-leading-order analysis of $V$+jet production at hadron colliders. The focus of this talk will be on new results on the full electroweak corrections to $Z(to l^-l^+)$+jet production at the LHC. All off-shell effects are included in our approach, and the finite lifetime of the $Z$ boson is consistently accounted for using the complex-mass scheme. In the following, we briefly introduce the calculation and discuss selected phenomenological implications of our results.
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The implementation of the full next-to-leading order (NLO) QCD corrections to electroweak Higgs boson plus three jet production at hadron colliders such as the LHC within the Matchbox NLO framework of the Herwig++ event generator is discussed. We present numerical results for integrated cross sections and kinematic distributions.
This paper summarises results on W and Z plus jet production in pp collisions at $sqrt{s} = 7$ TeV at the CERN Large Hadron Collider, from both the ATLAS and CMS experiments. Based on the 2010 and 2011 datasets, measurements have been made of numerous cross sections providing excellent tests of the latest predictions from QCD calculations and event generators.
First results on the radiative corrections of order O(N_falpha_salpha) are presented for the off-shell production of W or Z bosons at the LHC, where N_f is the number of fermion flavours. These corrections comprise all diagrams at O(alpha_salpha) with closed fermion loops, form a gauge-invariant part of the next-to-next-to-leading-order corrections of mixed QCD x electroweak type, and are the ones that concern the issue of mass renormalization of the W and Z resonances. The occurring irreducible two-loop diagrams, which involve only self-energy insertions, are calculated with current standard techniques, and explicit analytical results on the electroweak gauge-boson self-energies at O(alpha_salpha) are given. Moreover, the generalization of the complex-mass scheme for a gauge-invariant treatment of the W/Z resonances is described for the order O(alpha_salpha). While the corrections, which are implemented in the Monte Carlo program RADY, are negligible for observables that are dominated by resonant W/Z bosons, they affect invariant-mass distributions at the level of up to 2% for invariant masses of >500 GeV and are, thus, phenomenologically relevant. The impact on transverse-momentum distributions is similar, taking into account that leading-order predictions to those distributions underestimate the spectrum.
Radiative corrections of strong and electroweak interactions are presented at next-to-leading order for the production of a Higgs boson plus two hard jets via weak interactions at the LHC. The calculation includes all weak-boson fusion and quark-antiquark annihilation diagrams as well as the corresponding interferences. The electroweak corrections, which are discussed here for the first time, reduce the cross sections by 5%, and thus are of the same order of magnitude as the QCD corrections. As argued in previous papers, where s-channel diagrams and interferences were neglected, the QCD corrections connected to interference effects are small.
We present a state-of-the-art calculation of the next-to-leading-order electroweak corrections to ZZ production, including the leptonic decays of the Z bosons into $mu^+mu^-mathrm{e}^+mathrm{e}^-$ or $mu^+mu^-mu^+mu^-$ final states. We use complete leading-order and next-to-leading-order matrix elements for four-lepton production, including contributions of virtual photons and all off-shell effects of Z bosons, where the finite Z-boson width is taken into account using the complex-mass scheme. The matrix elements are implemented into Monte Carlo programs allowing for the evaluation of arbitrary differential distributions. We present integrated and differential cross sections for the LHC at 13 TeV both for an inclusive setup where only lepton identification cuts are applied, and for a setup motivated by Higgs-boson analyses in the four-lepton decay channel. The electroweak corrections are divided into photonic and purely weak contributions. The former show the well-known pronounced tails near kinematical thresholds and resonances; the latter are generically at the level of $sim-5%$ and reach several $-10%$ in the high-energy tails of distributions. Comparing the results for $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ final states, we find significant differences mainly in distributions that are sensitive to the $mu^+mu^-$ pairing in the $mu^+mu^-mu^+mu^-$ final state. Differences between $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ channels due to interferences of equal-flavour leptons in the final state can reach up to $10%$ in off-shell-sensitive regions. Contributions induced by incoming photons, i.e. photon-photon and quark-photon channels, are included, but turn out to be phenomenologically unimportant.
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