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This note presents the prospects of searches for new heavy resonances decaying to diboson (WW) and measurements of electroweak WW/WZ production via vector boson scattering (VBS) in association with a high-mass dijet system in the $ell u qq$ final states ($Wtoell u$, $W/Zto qq$). The prospects are presented for an integrated luminosity of 15 ab$^{-1}$ of proton-proton ($pp$) collisions at $sqrt{s}=27$ TeV with an ATLAS-like detector simulated in the Delphes framework. The cross-section measurement of the electroweak $WW/WZ$ production in VBS processes is expected to reach the precision of $sim$2-3%, improving the expected accuracy at the HL-LHC by a factor of 2. Prospects are presented also for the separation of the longitudinal component of the electroweak $WW/WZ$ production, showing the expected significance of $sim3sigma$ is reached with 3 ab$^{-1}$ for the single $ell u qq$ channel and $sim5sigma$ for all the semi-leptonic channels combined. The diboson resonance searches are interpreted for sensitivity to a simplified phenomenological model with a heavy gauge boson. With 15 ab$^{-1}$ of $pp$ data, the discovery reach for the new resonance is extended to 8 TeV.
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Longitudinal vector boson scattering provides an important probe of electroweak symmetry breaking, bringing sensitivity to physics beyond the Standard Model as well as constraining properties of the Higgs boson. It is a difficult process to study due to the small production cross section and challenging separation of the different polarization states. We study the sensitivity to longitudinal $WV$ vector boson scattering at the High-Luminosity Large Hadron Collider in semi-leptonic final states. While these are characterized by larger background contributions compared to fully leptonic final states, they benefit from a higher signal cross section due to the enhanced branching fraction. We determine the polarization through full reconstruction of the event kinematics using the $W$ boson mass constraint and through the use of jet substructure. We show that with these techniques sensitivities around three standard deviations at the HL-LHC are achievable, which makes this channel competitive with its fully leptonic counterparts.
We present a phenomenology study on central exclusive production of $W^+W^-$ boson pairs in proton-proton collisions at the Large Hadron Collider at 14 TeV using the forward proton detectors, such as the ATLAS Forward Proton or the CMS-TOTEM Precision Proton Spectrometer detectors. Final states where at least one of the $W$ bosons decay hadronically in a large-radius jet are considered. The latter extends previous efforts that consider solely leptonic final states. A measurement of exclusive $W^+W^-$ also allows us to further constrain anomalous quartic gauge boson interactions between photons and $W$ bosons. Expected limits on anomalous quartic gauge couplings $a_{0,C}^W$ associated to dimension-six effective operators are derived for the hadronic, semi-leptonic, and leptonic final states. It is found that the couplings can be probed down to one-dimensional values of $a_{0}^W = 3.7times 10^{-7}$ GeV$^{-2}$ and $a_{C}^W = 9.2 times 10^{-7}$ GeV$^{-2}$ at $95%$ CL at an integrated luminosity of 300 fb$^{-1}$ by combining all final states, compared to values of about $a_{0}^W = 4times 10^{-6}$ GeV$^{-2}$ and $a_{C}^W = 1times 10^{-5}$ GeV$^{-2}$ at 95% CL expected for the leptonic channel alone.
In the present work we study the production of vector resonances at the LHC by means of the vector boson scattering $WZ to WZ$ and explore the sensitivities to these resonances for the expected future LHC luminosities. We are assuming that these vector resonances are generated dynamically from the self interactions of the longitudinal gauge bosons, $W_L$ and $Z_L$, and work under the framework of the electroweak chiral Lagrangian to describe in a model independent way the supposedly strong dynamics of these modes. The properties of the vector resonances, mass, width and couplings to the $W$ and $Z$ gauge bosons are derived from the inverse amplitude method approach. We implement all these features into a single model, the IAM-MC, adapted for MonteCarlo, built in a Lagrangian language in terms of the electroweak chiral Lagrangian and a chiral Lagrangian for the vector resonances, which mimics the resonant behavior of the IAM and provides unitary amplitudes. The model has been implemented in MadGraph, allowing us to perform a realistic study of the signal versus background events at the LHC. In particular, we have focused our study on the $ppto WZjj$ type of events, discussing first on the potential of the hadronic and semileptonic channels of the final $WZ$, and next exploring in more detail the clearest signals. These are provided by the leptonic decays of the gauge bosons, leading to a final state with $ell_1^+ell_1^-ell_2^+ u jj$, $ell=e,mu$, having a very distinctive signature, and showing clearly the emergence of the resonances with masses in the range of 1.5-2.5 TeV, which we have explored.
Vector-boson scattering (VBS) processes probe the innermost structure of electroweak interactions in the Standard Model, and provide a unique sensitivity for new physics phenomena affecting the gauge sector. In this review, we report on the salient aspects of this class of processes, both from the theory and experimental point of view. We start by discussing recent achievements relevant for their theoretical description, some of which have set important milestones in improving the precision and accuracy of the corresponding simulations. We continue by covering the development of experimental techniques aimed at detecting these rare processes and improving the signal sensitivity over large backgrounds. We then summarise the details of the most relevant VBS signatures and review the related measurements available to date, along with their comparison with Standard-Model predictions. We conclude by discussing the perspective at the upcoming Large Hadron Collider runs and at future hadron facilities.
We present a systematic interpretation of vector boson scattering (VBS) and diboson measurements from the LHC in the framework of the dimension-six Standard Model Effective Field Theory (SMEFT). We consider all available measurements of VBS fiducial cross-sections and differential distributions from ATLAS and CMS, in most cases based on the full Run II luminosity, and use them to constrain 16 independent directions in the dimension-six EFT parameter space. Compared to the diboson measurements, we find that VBS provides complementary information on several of the operators relevant for the description of the electroweak sector. We also quantify the ultimate EFT reach of VBS measurements via dedicated projections for the High Luminosity LHC. Our results motivate the integration of VBS processes in future global SMEFT interpretations of particle physics data.
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