Evidence is reported for electroweak (EW) vector boson scattering in the decay channel ℓνqq of two weak vector bosons WV (V=W or Z), produced in association with two parton jets. The search uses a ...data set of proton-proton collisions at 13 TeV collected with the CMS detector during 2016–2018 with an integrated luminosity of 138fb−1. Events are selected requiring one lepton (electron or muon), moderate missing transverse momentum, two jets with a large pseudorapidity separation and a large dijet invariant mass, and a signature consistent with the hadronic decay of a W/Z boson. The cross section is computed in a fiducial phase space defined at parton level requiring all parton transverse momenta pT>10GeV and at least one pair of outgoing partons with invariant mass mqq>100GeV. The measured and expected EW WV production cross sections are 1.90−0.46+0.53pb and 2.23−0.11+0.08(scale)±0.05(PDF)pb, respectively, where PDF is the parton distribution function. The observed EW signal strength is μEW=0.85±0.12(stat)−0.17+0.19(syst), corresponding to a signal significance of 4.4 standard deviations with 5.1 expected, and it is measured keeping the quantum chromodynamics (QCD) associated diboson production fixed to the standard model prediction. This is the first evidence of vector boson scattering in the ℓνqq decay channel at LHC. The simultaneous measurement of the EW and QCD associated diboson production agrees with the standard model prediction.
A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron ...or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak Wγjj production in a restricted fiducial region is measured as 20.4±4.5fb and the total cross section for Wγ production in association with 2 jets in the same fiducial region is 108±16fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators.
We study the polarization of positively charged W's in the scattering of massive electroweak bosons at hadron colliders. We rely on the separation of weak boson polarizations in the gauge-invariant, ...doubly-resonant part of the amplitude in Monte Carlo simulations. Polarizations depend on the reference frame in which they are defined. We discuss the change in polarization fractions and in kinematic distributions arising from defining polarization vectors in two different reference frames which have been employed in recent experimental analyses.
How relevant are top loops in VBS at the LHC? Quezada-Calonge, Carlos; Dobado, Antonio; Sanz-Cillero, Juan José
Nuclear and particle physics proceedings,
March 2023, 2023-03-00, Volume:
324-329
Journal Article
Peer reviewed
Open access
We present the contributions to the imaginary part of the W+W− elastic scattering from top and bottom quark one-loop diagrams. The computation is performed within the context of HEFT, where we ...compare them with the boson-loop corrections. We argue that the often neglected (top and bottom) fermion contributions may in fact be relevant.
Boson-Boson Interactions at the LHC Manjarrés Ramos, J; Gómez-Ceballos, Guillelmo
Annual review of nuclear and particle science,
09/2023, Volume:
73, Issue:
1
Journal Article
Peer reviewed
Open access
Vector boson scattering is a key production process to probe the electroweak symmetry breaking of the Standard Model and is one of the most important topics of the physics program for the HL-LHC ...since it involves both self-couplings of vector bosons and their coupling with the Higgs boson. If the Higgs mechanism is not the sole source of electroweak symmetry breaking, the scattering amplitude deviates from the Standard Model prediction at high scattering energy. Moreover, deviations may be detectable even if a New Physics scale is higher than the reach of direct searches. In this review, the most recent experimental measurements of the production cross sections of vector boson pairs in association with two jets in proton-proton collisions at
TeV at the LHC are reported, using data sets recorded by the ATLAS and CMS detectors. Applications to searches for New Physics, as well as prospects for measuring the electroweak vector boson scattering processes with larger data samples, are also summarized.
Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely ...predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented.
Abstract
Vector boson scattering at the Large Hadron Collider (LHC) is sensitive to anomalous quartic gauge couplings (aQGCs). In this study, we investigate the aQGC contribution to
Wγjj
production ...at the LHC with
TeV in the context of an effective field theory (EFT). The unitarity bound is applied as a cut on the energy scale of this production process, which is found to have significant suppressive effects on signals. To enhance the statistical significance, we analyze the kinematic and polarization features of the aQGC signals in detail. We find that the polarization effects induced by aQGCs are unique and can discriminate the signals from the SM backgrounds well. With the proposed event selection strategy, we obtain the constraints on the coefficients of dimension-8 operators with current luminosity. The results indicate that the process
is powerful for searching for the
and
operators.
Parameterization of heavy effects beyond the Standard Model is available using higher-dimension operators of the effective field theory and their Wilson coefficients, where their values are not ...known. Experimental sensitivity to the Wilson coefficients can be significantly changed in case of the usage of composite anomalous signal, which contains anomalous contributions from background processes in addition to the conventional ones from the signal process. In this work, this approach is applied to the search for anomalous quartic gauge couplings with seven EFT operators in the electroweak production of ZZ(→ ℓℓνν)jj and Zγ(→ ννγ)jj in pp collisions. For the majority of coefficients, sensitivity in the former channel is smaller than that in the latter one. However, it is shown, that composite anomalous signal affects ZZ(→ ℓℓνν)jj production stronger than Zγ(→ ννγ)jj production, making sensitivities closer. One-dimensional limits on theWilson coefficients are changed up to 27.3% and 9.7% due to the background anomalous contributions in ZZ(→ ℓℓνν)jj and Zγ(→ ννγ)jj productions, respectively.
We report on a consistent comparison between techniques of quantum and classical machine learning applied to the classification of signal and background events for the Vector Boson Scattering ...processes, studied at the Large Hadron Collider installed at the CERN laboratory. Quantum machine learning algorithms based on variational quantum circuits are run on freely available quantum computing hardware, showing very good performances as compared to deep neural networks run on classical computing facilities. In particular, we show that such kind of quantum neural networks is able to correctly classify the targeted signal with an Area Under the characteristic Curve (AUC) that is very close to the one obtained with the corresponding classical neural network, but employing a much lower number of resources, as well as less variable data in the training set. Albeit giving a proof-of-principle demonstration with limited quantum computing resources, this work represents one of the first steps towards the use of near term and noisy quantum hardware for practical event classification in High Energy Physics experiments.
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