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Register a new userPolarisation at NLO in WZ production at the LHC
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The pair production of a $W$ and a $Z$ boson at the LHC is an important process to study the triple-gauge boson couplings as well as to probe new physics that could arise in the gauge sector. In particular the leptonic channel $p p to W^pm Zto 3ell + u + X$ is considered by ATLAS and CMS collaborations. Polarisation observables can help pinning down new physics and give information on the spin of the gauge bosons. Measuring them requires high statistics as well as precise theoretical predictions. We define in this contribution fiducial polarisation observables for the $W$ and $Z$ bosons and we present theoretical predictions in the Standard Model at next-to-leading order (NLO) including QCD as well as NLO electroweak corrections, the latter in the double-pole approximation. We also show that this approximation works remarkably well for $W^pm Z$ production at the LHC by comparing to the full results.
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Accessing the polarization of weak bosons provides an important probe for the mechanism of electroweak symmetry breaking. Relying on the double-pole approximation and on the separation of polarizations at the amplitude level, we study WZ production at the LHC, with both bosons in a definite polarization mode, including NLO QCD effects. We compare results obtained defining the polarization vectors in two different frames. Integrated and differential cross-sections in a realistic fiducial region are presented.
The production of WWZ at the LHC is an important process to test the quartic gauge couplings of the Standard Model as well as an important background for new physics searches. A good theoretical understanding at next-to-leading order (NLO) is therefore valuable. In this paper, we present the calculation of the NLO electroweak (EW) correction to this channel with on-shell gauge bosons in the final state. It is then combined with the NLO QCD correction to get the most up-to-date prediction. We study the impact of these corrections on the total cross section and some distributions. The NLO EW correction is small for the total cross section but becomes important in the high energy regime for the gauge boson transverse momentum distributions.
We present a study of the polarization observables of the $W$ and $Z$ bosons in the process $p p to W^pm Zto e^pm u_e mu^+mu^-$ at the 13 TeV Large Hadron Collider. The calculation is performed at next-to-leading order, including the full QCD corrections as well as the electroweak corrections, the latter being calculated in the double-pole approximation. The results are presented in the helicity coordinate system adopted by ATLAS and for different inclusive cuts on the di-muon invariant mass. We define left-right charge asymmetries related to the polarization fractions between the $W^+ Z$ and $W^- Z$ channels and we find that these asymmetries are large and sensitive to higher-order effects. Similar findings are also presented for charge asymmetries related to a P-even angular coefficient.
The tri-boson production is one of the key processes for the study of quartic gauge couplings. Next-to-leading order (NLO) corrections are mandatory to reduce theoretical uncertainties. In this study, the most up-to-date predictions including NLO QCD and NLO EW corrections to the total cross section and distributions of the WWZ production at the LHC are presented. We show that the QCD correction is about 100% and the EW correction is of a few percent at the total cross section level. The EW correction however becomes significant in the high energy regime of the gauge boson transverse momentum distributions.
We obtain predictions accurate at the next-to-leading order in QCD for the production of a generic spin-two particle in the most relevant channels at the LHC: production in association with coloured particles (inclusive, one jet, two jets and $tbar t$), with vector bosons ($Z,W^pm,gamma$) and with the Higgs boson. We present total and differential cross sections as well as branching ratios as a function of the mass and the collision energy also considering the case of non-universal couplings to standard model particles. We find that the next-to-leading order corrections give rise to sizeable $K$ factors for many channels, in some cases exposing the unitarity-violating behaviour of non-universal couplings scenarios, and in general greatly reduce the theoretical uncertainties. Our predictions are publicly available in the MadGraph5_aMC@NLO framework and can, therefore, be directly used in experimental simulations of spin-two particle production for arbitrary values of the mass and couplings.
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