Providing accurate theoretical predictions in the Standard Model for processes with polarised electroweak bosons is crucial to understand more in-depth the electroweak-symmetry breaking mechanism and to enhance the sensitivity to potential new-physics effects. Motivated by the rapidly increasing number of polarisation analyses of di-boson processes with LHC data, we carry out a comprehensive study of the inclusive production of two polarised Z bosons in the decay channel with four charged leptons. We perform a detailed comparison of fixed-order predictions obtained with various Monte Carlo programs which rely on different signal-definition strategies, assessing non-resonant and interference effects by contrasting polarised results with unpolarised and full off-shell ones. For the first time, we accomplish the combination of NNLO QCD and NLO EW corrections, setting the new state-of-the-art perturbative accuracy for polarised Z-boson pairs at the LHC. The impact of parton-shower matching and multi-jet merging is investigated by scrutinising calculations obtained with event generators that are typically used in experimental analyses. Integrated and differential results are discussed in a realistic fiducial setup and compared to publicly available ATLAS results.

Italy

Costanza Carrivale

Roberto Covarelli

Germany

Ansgar Denner

China

Dongshuo Du

Christoph Haitz

Mareen Hoppe

United States

Martina Javurkova

Vietnam

Duc Le

Jakob Linder

Rafael Sa

Belgium

Olivier Mattelaer

Susmita Mondal

Giacomo Ortona

Giovanni Pelliccioli

Poland

Rene Poncelet

United Kingdom

Karolos Potamianos

Richard Ruiz

Marek Schönherr

Frank Siegert

Lailin Xu

Xingyu Wu

Giulia Zanderighi

Precise standard-model predictions for polarised Z-boson pair production and decay at the LHC

We present the first calculation of same-sign WW scattering at the LHC in the fully leptonic decay channel including the modelling of polarisation for intermediate electroweak bosons and radiative corrections up to NLO EW+QCD accuracy. The predictions rely on a pole expansion and on the split of polarisation states at matrix-element level. Doubly-polarised and unpolarised signals are investigated together with full off-shell results. A detailed phenomenlogical analysis is carried out focusing on differential observables that discriminate between polarisation states, paving the way for refined polarisation-oriented analyses of vector-boson scattering with Run-3 LHC data.

NLO EW and QCD corrections to polarised same-sign WW scattering at the LHC

Tri-boson production together with vector-boson scattering is a privileged channel to study the electroweak structure of the Standard Model. Upcoming LHC running stages will allow to measure these processes at unprecedented accuracy and for all possible final states, which requires to push theory predictions to still unexplored frontiers. In this work we present the first calculation for the process pp → μ + μ  − e+ ν ejj at the LHC in a tri-boson phase space. We evaluate the three LO contributions, namely the   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (α 6), which contains the genuine tri-boson signature, along with the   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (α s α 5) and   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (  <math> <msubsup> <mi>α</mi> <mi>s</mi> <mn>2</mn> </msubsup> </math>  $$ {\alpha}_{\textrm{s}}^2 $$  α 4), and the two   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (α 7) and   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (α s α 6) NLO corrections. The calculation is based on full Standard-Model matrix elements, including all resonant and non-resonant terms, complete spin correlations and interference effects. Integrated and differential cross sections are presented for a fiducial region inspired by High Luminosity LHC prospect studies. We find electroweak corrections of −14% for the fiducial cross section, almost twice as large as for other tri-boson processes.

Daniele Lombardi

Santiago Lopez Portillo Chavez

NLO corrections to triple vector-boson production in final states with three charged leptons and two jets

Measuring vector-boson scattering beyond the fully-leptonic final state is becoming possible at the LHC, which demands to have a solid control on the theory predictions for all final states of this class of processes. In this work we present a full off-shell leading-order calculation for the process pp → ℓ + ν  ℓ  + 4j in two fiducial regions which are particularly relevant for its experimental measurement. In addition to the fully electroweak order, i.e.   <math> <mi>O</mi> <mfenced> <msup> <mi>α</mi> <mn>6</mn> </msup> </mfenced> </math>  $$ \mathcal{O}\left({\alpha}^6\right) $$ , we complement our results with   <math> <mi>O</mi> <mfenced> <mrow> <msub> <mi>α</mi> <mi>s</mi> </msub> <msup> <mi>α</mi> <mn>5</mn> </msup> </mrow> </mfenced> </math>  $$ \mathcal{O}\left({\alpha}_{\textrm{s}}{\alpha}^5\right) $$  and   <math> <mi>O</mi> <mfenced> <mrow> <msubsup> <mi>α</mi> <mi>s</mi> <mn>2</mn> </msubsup> <msup> <mi>α</mi> <mn>4</mn> </msup> </mrow> </mfenced> </math>  $$ \mathcal{O}\left({\alpha}_{\textrm{s}}^2{\alpha}^4\right) $$  for inclusive predictions. At   <math> <mi>O</mi> <mfenced> <msup> <mi>α</mi> <mn>6</mn> </msup> </mfenced> </math>  $$ \mathcal{O}\left({\alpha}^6\right) $$  we present for the first time a systematic treatment of the process in double-pole approximation and we perform a detailed study of its range of validity by considering inclusive and differential predictions compared to the full off-shell calculation.

Christopher Schwan

Double-pole approximation for leading-order semi-leptonic vector-boson scattering at the LHC

In this work, we present the first full NLO predictions for the process pp → μ + ν  μ e+ ν ejj at the LHC in a typical tri-boson phase space. The NLO corrections reach 50% at the level of the fiducial cross section and have a very different hierarchy with respect to vector-boson-scattering phase spaces. By comparing the cross section of the full off-shell process with the sum of contributing on-shell electroweak-boson production subchannels, we find that the process is dominated by WWW and WH production, while vector-boson-scattering topologies still play a non-negligible role. In addition, NLO QCD predictions matched to parton shower which are supplemented by approximate electroweak corrections are provided. For the fiducial cross section, the electroweak corrections turn out to be small but the QCD corrections reach 47%. For the inclusive cross section, matching to parton shower affects the predictions by 7%. However, for differential distributions corrections due to the parton shower can be much more sizeable, depending on the region of phase space.

Mathieu Pellen

Steffen Schumann

Tri-boson and WH production in the W + W + jj channel: predictions at full NLO accuracy and beyond

At energies that are large with respect to the electroweak scale, the electroweak corrections to scattering processes involve large logarithms that have to be resummed to obtain decent predictions. Soft-collinear effective theory (SCET) has been proposed as a suitable framework to allow for this resummation, while retaining non-logarithmic corrections in a consistent way. In this paper, we investigate the approximations needed to use this approach for the calculation of electroweak corrections to off-shell diboson production at high-energy colliders. Upon implementing the method into a Monte-Carlo integration code, we provide resummed predictions for cross sections and distributions at a  $$3\,\text {TeV} $$  <math> <mrow> <mn>3</mn> <mspace width="0.166667em"></mspace> <mtext>TeV</mtext> </mrow> </math>   lepton collider and a  $$100\,\text {TeV} $$  <math> <mrow> <mn>100</mn> <mspace width="0.166667em"></mspace> <mtext>TeV</mtext> </mrow> </math>   proton collider.

Stefan Rode

Automated resummation of electroweak Sudakov logarithms in diboson production at future colliders

In this letter we present results for next-to-leading-order electroweak corrections to doubly polarised <math><msup><mrow><mtext>W</mtext></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mtext>W</mtext></mrow><mrow><mo>−</mo></mrow></msup></math> production at the LHC in the fully leptonic decay channel. We model the production and the decay of two polarised W bosons in the double-pole approximation, including factorisable real and virtual electroweak corrections, and separating polarisation states at amplitude level. We obtain integrated and differential predictions for polarised signals in a realistic fiducial setup.

NLO EW corrections to polarised W W production and decay at the LHC

Measuring precisely top-pair-associated processes at hadron colliders will become possible with the upcoming LHC running stages. The increased data statistics will especially enable differential measurements leading to an improved characterisation of such processes. Aiming at a consistent data-theory comparison, precise Standard-Model predictions are needed, including higher-order corrections and full off-shell effects. In this work we present NLO-accurate predictions for the production and decay of a top-antitop pair in association with a Z boson at the LHC, in the multi-lepton decay channel. The complete set of LO contributions and NLO corrections of EW and QCD origin is included. The calculation is based on full matrix elements, computed with all resonant and non-resonant contributions, complete spin correlations and interference effects. Integrated and differential cross-sections are presented for a realistic fiducial setup.

Complete NLO corrections to off-shell   <math> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> <mi>Z</mi> </math>  $$ \textrm{t}\overline{\textrm{t}}\textrm{Z} $$  production at the LHC

The study of top-quark properties will be a central aspect of the physics programme of any future lepton collider. In this article, we investigate the production of top-quark pairs in the semi-leptonic decay channel in  $${\textrm{e}}^{+}\textrm{e}^{-}$$  <math> <mrow> <msup> <mrow> <mtext>e</mtext> </mrow> <mo>+</mo> </msup> <msup> <mtext>e</mtext> <mo>-</mo> </msup> </mrow> </math>   collisions, whose experimental signature is one charged lepton, jets, and missing energy. We present for the first time fiducial cross sections and differential distributions at next-to-leading-order accuracy in QCD for the full off-shell process. We find that the QCD corrections for the considered process are strongly dependent on the beam energies and range from few per cent up to more than  $$100\%$$  <math> <mrow> <mn>100</mn> <mo>%</mo> </mrow> </math>   (near threshold and above  $$1\,\text {TeV} $$  <math> <mrow> <mn>1</mn> <mspace width="0.166667em"></mspace> <mtext>TeV</mtext> </mrow> </math>  ). We focus, in particular, on two scenarios: one close to threshold ( $$365\,\text {GeV} $$  <math> <mrow> <mn>365</mn> <mspace width="0.166667em"></mspace> <mtext>GeV</mtext> </mrow> </math>  ), dominated by top-pair production, and one at the TeV scale ( $$1.5\,\text {TeV} $$  <math> <mrow> <mn>1.5</mn> <mspace width="0.166667em"></mspace> <mtext>TeV</mtext> </mrow> </math>  ), for which irreducible-background contributions become relevant. An assessment of polarised-beam effects is also provided.

NLO QCD corrections to off-shell top–antitop production with semi-leptonic decays at lepton colliders

Understanding the polarization structure and providing precise predictions for multiboson processes at the LHC is becoming urgent in the light of the upcoming run-3 and high-luminosity data. The CMS and ATLAS collaborations have already started using polarized predictions to perform template fits of the data, getting access to the polarization of W and Z bosons. So far, only fully leptonic decay channels have been considered in this perspective. The natural step forward is the investigation of hadronic decays of electroweak bosons. In this work, we compute NLO QCD corrections to the production and decay of WZ pairs at the LHC in final states with two charged leptons and jets. The calculation relies on the double-pole approximation and the separation of polarized states at the level of Standard Model amplitudes. The presented NLO-accurate results are necessary building blocks for a broad understanding and precise modeling of polarized diboson production in semileptonic decay channels.

NLO QCD corrections to polarized diboson production in semileptonic final states