Polarisation at NLO in WZ production at the LHC

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 $p p \to W^\pm Z\to 3\ell +\nu + X$ 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.Comment: 6 pages, 2 figures, 2 tables. Contribution to the proceedings of the 54th Rencontres de Moriond, EW interactions and unified theory, March 16-23 2019, La Thuile, Ital

Fiducial polarization observables in hadronic WZ production: A next-to-leading order QCD+EW study

We present a study at next-to-leading-order (NLO) of the process $pp \to W^\pm Z \to \ell \nu_l \ell'^+ \ell'^-$, where $\ell,\ell' =e, \mu$, at the Large Hadron Collider. We include the full NLO QCD corrections and the NLO electroweak (EW) corrections in the double-pole approximation. We define eight fiducial polarization coefficients directly constructed from the polar-azimuthal angular distribution of the decay leptons. These coefficients depend strongly on the kinematical cuts on the transverse momentum or rapidity of the individual leptons. Similarly, fiducial polarization fractions are also defined and they can be directly related to the fiducial coefficients. We perform a detailed analysis of the NLO QCD+EW fiducial polarization observables including theoretical uncertainties stemming from the scale variation and parton distribution function uncertainties, using the fiducial phase space defined by the ATLAS and CMS experiments. We provide results in the helicity coordinate system and in the Collins-Soper coordinate system, at a center-of-mass energy of 13 TeV. The EW corrections are found to be important in two of the angular coefficients related to the $Z$ boson, irrespective of the kinematical cuts or the coordinate system. Meanwhile, those EW corrections are very small for the $W^\pm$ bosons.Comment: Substantial improvement after useful comments from the anonymous referee: Numerical results for the EW corrections to the cross sections and distributions shifted by -5 (-2)% for ATLAS (CMS) cuts after fixing a bug in the momentum assignment in some cut and histogram routines; results for polarization observables marginally affected, hence conclusions for them unchanged; published versio

On the triplet anti-triplet symmetry in 3-3-1 models

We present a detailed discussion of the triplet anti-triplet symmetry in 3-3-1 models. The full set of conditions to realize this symmetry is provided, which includes in particular the requirement that the two vacuum expectation values of the two scalar triplets responsible for making the W and Z bosons massive must be interchanged. We apply this new understanding to the calculation of processes that have a Z-Z' mixing.Comment: 14 page