Vector Boson Fusion Processes Research Articles

Probing the CP structure of the top quark Yukawa at the future muon collider

We study the top-Higgs coupling with a CP violating phase ξ at a future multi-TeV muon collider. We focus on processes that are directly sensitive to the top quark Yukawa coupling: tt¯h\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t}h $$\\end{document}, tbhμν, and tt¯hνν¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t} h\ u \\overline{\ u} $$\\end{document} with h→bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ h\ o b\\overline{b} $$\\end{document} and semileptonic top decays. At different energies, different processes dominate the cross section, providing complementary information. At and above an energy of O10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}(10) $$\\end{document} TeV, vector boson fusion processes dominate. As we show, in the Standard Model there is destructive interference in the vector boson fusion processes tt¯hνν¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t} h\ u \\overline{\ u} $$\\end{document} and tbhμν between the top quark Yukawa and Higgs-gauge boson couplings. A CP-violating phase changes this interference, and the cross section measurement is very sensitive to the size of the CP-violating angle. Although we find that the cross sections are measured to O50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}\\left(50\\%\\right) $$\\end{document} statistical uncertainty at 1σ, a 10 and 30 TeV muon collider can bound the CP-violating angle |ξ| ≲ 9.0° and |ξ| ≲ 5.4°, respectively. However, cross section measurements are insensitive to the sign of the CP-violating angle. To determine that the coupling is truly CP violating, observables sensitive to CP-violation must be measured. We find in the tt¯h\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t}h $$\\end{document} process the azimuthal angle between the t+t¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t+\\overline{t} $$\\end{document} plane and the initial state muon+Higgs plane shows good discrimination for ξ = ±0.1π. For the tbhμν and tt¯hνν¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ t\\overline{t} h\ u \\overline{\ u} $$\\end{document} processes, the operator proportional to p→μ×p→h\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\left({\\overrightarrow{p}}_{\\mu}\ imes {\\overrightarrow{p}}_h\\right) $$\\end{document} · p→t\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overrightarrow{p}}_t $$\\end{document} is sensitive to the sign of CP phase ξ. From these observables, we construct asymmetry parameters that show good distinction between different values and signs of the CP violating angle.

Measurement and interpretation of same-sign W boson pair production in association with two jets in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ATLAS detector

This paper presents the measurement of fiducial and differential cross sections for both the inclusive and electroweak production of a same-sign W-boson pair in association with two jets (W±W±jj) using 139 fb−1 of proton-proton collision data recorded at a centre-of-mass energy of s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed by selecting two same-charge leptons, electron or muon, and at least two jets with large invariant mass and a large rapidity difference. The measured fiducial cross sections for electroweak and inclusive W±W±jj production are 2.92 ± 0.22 (stat.) ± 0.19 (syst.) fb and 3.38 ± 0.22 (stat.) ± 0.19 (syst.) fb, respectively, in agreement with Standard Model predictions. The measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confidence level intervals on dimension-8 operators. A search for doubly charged Higgs bosons H±± that are produced in vector-boson fusion processes and decay into a same-sign W boson pair is performed. The largest deviation from the Standard Model occurs for an H±± mass near 450 GeV, with a global significance of 2.5 standard deviations.

Search for Higgs Boson Production via Vector Boson Fusion Process with Subsequent $$H \to b\bar {b}$$ Decay with CMS Experiment at LHC

Search for Higgs Boson Production via Vector Boson Fusion Process with Subsequent $$H \to b\bar {b}$$ Decay with CMS Experiment at LHC

Next-to-leading-logarithmic PanScales showers for deep inelastic scattering and vector boson fusion

We introduce the first family of parton showers that achieve next-to-leading logarithmic (NLL) accuracy for processes involving a t-channel exchange of a colour-singlet, and embed them in the PanScales framework. These showers are applicable to processes such as deep inelastic scattering (DIS), vector boson fusion (VBF), and vector boson scattering (VBS). We extensively test and verify the NLL accuracy of the new showers at both fixed order and all orders across a wide range of observables. We also introduce a generalisation of the Cambridge-Aachen jet algorithm and formulate new DIS observables that exhibit a simple resummation structure. The NLL showers are compared to a standard transverse-momentum ordered dipole shower, serving as a proxy for the current state-of-the-art leading-logarithmic showers available in public codes. Depending on the observable, we find discrepancies at NLL of the order of 15%. We also present some exploratory phenomenological results for Higgs production in VBF. This work enables, for the first time, to resum simultaneously global and non-global observables for the VBF process at NLL accuracy.

Measuring lepton number violation in heavy neutral lepton decays at the future muon collider

The future muon collider has the potential to discover feebly interacting particles in a wide range of masses above the electroweak scale. It is particularly suitable to search for heavy neutral leptons (HNLs), as their production cross section σ∼mW−2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sigma \\sim {m}_W^{-2} $$\\end{document} is not suppressed by the new physics scale. We demonstrate that with the capacity to observe up to 105 events in the previously unexplored TeV mass range, the muon collider provides the means to measure the fraction of lepton number violating (LNV) processes with precision at the level of a percent. This capability enables elucidating the nature of HNLs, allowing us to differentiate between Majorana, Dirac, and non-minimal scenarios featuring multiple degenerate HNLs. We link the observed fraction of LNV processes to the parameters of the model with three degenerate HNLs, which could be responsible for generating baryon asymmetry in the Universe. Additionally, we present a simple estimate for the number of signal events, as well as analyze the feasibility of vector boson fusion processes in searches for HNLs.

Higgs production at next generation e+e− colliders

In this study, Higgs production processes, Higgsstrahlung and vector boson ([Formula: see text] and [Formula: see text]) fusion processes, are investigated for four different future lepton colliders (CEPC, ILC, CLIC, and FCC-ee). The cross-sections for each production process and corresponding backgrounds are calculated considering the Initial State Radiation (ISR) and Beamstrahlung (BS) effects. Various cuts and the b-tagging method are used to reduce the background. Finally, the number of events for each collider is determined, and significance calculations are performed. In our calculations, high event numbers are obtained for all four colliders for the Higgsstrahlung, [Formula: see text], and [Formula: see text] fusion process. This shows that electron–positron colliders will play an important role in future Higgs physics research.

Search for nonresonant Higgs boson pair production in final state with two bottom quarks and two tau leptons in proton-proton collisions at [formula omitted

A search for the nonresonant production of Higgs boson pairs (HH ) via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of s=13TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138fb−1. Events in which at least one tau lepton decays hadronically are considered and multiple machine learning techniques are used to identify and extract the signal. The data are found to be consistent, within uncertainties, with the standard model (SM) predictions. Upper limits on the HH production cross section are set to constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to 3.3 (5.2) times the SM prediction for the inclusive HH cross section and to 124 (154) times the SM prediction for the vector boson fusion HH cross section. At 95% confidence level, the Higgs field self-coupling is constrained to be within −1.7 and 8.7 times the SM expectation, and the coupling of two Higgs bosons to two vector bosons is constrained to be within −0.4 and 2.6 times the SM expectation.

Revealing the origin of neutrino masses through the Type II Seesaw mechanism at high-energy muon colliders

The future muon collider can play as an ideal machine to search for new physics at high energies. In this work, we study the search potential of the heavy Higgs triplet in the Type II Seesaw mechanism at muon colliders with high collision energy and high luminosity. The latest neutrino oscillation data are taken into account for realizing the leptonic decay modes of the charged Higgs bosons (H±±, H±) in the Type II Seesaw. We show the impact of neutrino mass and mixing parameters on the purely leptonic decays. The pair production of doubly charged Higgs H++H−− is through direct μ+μ− annihilation and vector boson fusion (VBF) processes at muon collider. The associated production H±±H∓ can only be induced by VBF processes. We simulate both the purely leptonic and bosonic signal channels of charged Higgs bosons in Type II Seesaw, together with the Standard Model backgrounds. We show the required luminosity for the discovery of the charged Higgses and the reachable limits on the leptonic decay branching fractions.

Long-term LHC discovery reach for compressed Supersymmetry models using VBF processes

The identity of Dark Matter (DM) is one of the most active topics in particle physics today. Supersymmetry (SUSY) is an extension of the standard model (SM) that could describe the particle nature of DM in the form of the lightest neutralino in R-parity conserving models. We focus on SUSY models that solve the hierarchy problem with small fine tuning, and where the lightest SUSY particles left({tilde{upchi}}_1^0,{tilde{upchi}}_1^{pm },{tilde{upchi}}_2^0right) are a triplet of higgsino-like states, such that the mass difference Delta mleft({tilde{upchi}}_2^0,{tilde{upchi}}_1^0right) is 0.5–50 GeV. We perform a feasibility study to assess the long-term discovery potential for these compressed SUSY models with higgsino-like states, using vector boson fusion (VBF) processes in the context of proton-proton collisions at sqrt{s} = 13 TeV, at the CERN Large Hadron Collider. Assuming an integrated luminosity of 3000 fb−1, we find that stringent VBF requirements, combined with large missing momentum and one or two low-pT leptons, is effective at reducing the major SM backgrounds, leading to a 5σ (3σ) discovery reach for mleft({tilde{upchi}}_2^0right) < 180 (260) GeV, and a projected 95% confidence level exclusion region that covers mleft({tilde{upchi}}_2^0right) up to 385 GeV, parameter space that is currently unconstrained by other experiments.

Probing heavy triplet leptons of the type-III seesaw mechanism at future muon colliders

We study the search potential of heavy triplet leptons in a type-III seesaw mechanism at future high-energy and high-luminosity muon colliders. The impact of up-to-date neutrino oscillation results is taken into account on neutrino parameters and the consequent decay patterns of heavy leptons in a type-III seesaw. The three heavy leptons in the Casas-Ibarra parametrization with diagonal unity matrix are distinguishable in their decay modes. We consider the pair production of charged triplet leptons ${E}^{+}{E}^{\ensuremath{-}}$ through both ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ annihilation and vector boson fusion (VBF) processes. The leading-order framework of electroweak parton distribution functions is utilized to calculate the VBF cross sections. The charged triplet leptons can be probed for masses above $\ensuremath{\sim}1\text{ }\text{ }\mathrm{TeV}$. The ${E}^{+}{E}^{\ensuremath{-}}\ensuremath{\rightarrow}ZZ{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ channel can be further utilized to fully reconstruct the three triplet leptons and distinguish neutrino mass patterns. The pair production of heavy neutrinos $N$ and the associated production ${E}^{\ifmmode\pm\else\textpm\fi{}}N$ are only induced by VBF processes and lead to a lepton-number-violating (LNV) signature. We also study the search potential of LNV processes at future high-energy muon colliders with $\sqrt{s}=30\text{ }\text{ }\mathrm{TeV}$.

Search for heavy resonances decaying to Z(νν¯)V(qq¯′) in proton-proton collisions at s=13 TeV

A search is presented for heavy bosons decaying to Z(νν¯)V(qq¯′), where V can be a W or a Z boson. A sample of proton-proton collision data at s=13 TeV was collected by the CMS experiment during 2016–2018. The data correspond to an integrated luminosity of 137 fb−1. The event categorization is based on the presence of high-momentum jets in the forward region to identify production through weak vector boson fusion. Additional categorization uses jet substructure techniques and the presence of large missing transverse momentum to identify W and Z bosons decaying to quarks and neutrinos, respectively. The dominant standard model backgrounds are estimated using data taken from control regions. The results are interpreted in terms of radion, W′ boson, and graviton models, under the assumption that these bosons are produced via gluon-gluon fusion, Drell–Yan, or weak vector boson fusion processes. No evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on various types of hypothetical new bosons. Observed (expected) exclusion limits on the masses of these bosons range from 1.2 to 4.0 (1.1 to 3.7) TeV.3 MoreReceived 16 September 2021Accepted 7 June 2022DOI:https://doi.org/10.1103/PhysRevD.106.012004Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the CMS CollaborationPhysics Subject Headings (PhySH)Physical SystemsHypothetical gauge bosonsTechniquesHadron collidersParticles & Fields

Doubly charged Higgs production at future ep colliders * *Supported in part by National Natural Science Foundation of China (11605075, 11635009) and Natural Science Foundation of Shandong Province (ZR2017JL006, ZR2021QA040)

The Higgs sector of the standard model can be extended by introducing an Higgs triplet Δ to generate tiny neutrino masses in the framework of the type-II seesaw mechanism. In this paper, we study the pair production of the introduced Higgs triplet at future colliders. The corresponding production cross sections via the vector boson fusion process at the FCC-ep and ILC FCC are predicted, where the production of a pair of doubly charged Higgs is found to be dominant and then used to investigate the collider phenomenology of the Higgs triplet. Depending on the size of the Higgs triplet vacuum expectation value, the doubly charged Higgs may decay into a pair of same-sign charged leptons or a pair of same-sign W bosons. To explore the discovery potential of the doubly charged Higgs at future colliders, we discuss these two decay scenarios in detail and show their detection sensitivity based on the mass of the doubly charged Higgs.

μTRISTAN

Abstract The ultra-cold muon technology developed for the muon g − 2 experiment at J-PARC provides a low-emittance μ+ beam which can be accelerated and used for realistic collider experiments. We consider the possibility of new collider experiments by accelerating the μ+ beam up to 1 TeV. Allowing the μ+ beam to collide with a high-intensity e− beam at the TRISTAN energy, $E_{e^-}= 30$ GeV, in a storage ring with the same size as TRISTAN (a circumference of 3 km), one can realize a collider experiment with the center-of-mass energy $\sqrt{s} = 346$ GeV, which allows the production of Higgs bosons through vector boson fusion processes. We estimate the deliverable luminosity with existing accelerator technologies to be at the level of 5 × 1033 cm−2 s−1, with which the collider can be a good Higgs boson factory. μ+μ+ colliders up to $\sqrt{s} = 2$ TeV are also possible using the same storage ring. They have the capability of producing the superpartner of the muon up to TeV masses.

Heavy Higgs bosons in 2HDM at a muon collider

We study the discovery potential of the non-Standard Model (SM) heavy Higgs bosons in the Two-Higgs-Doublet Models (2HDMs) at a multi-TeV muon collider and explore the discrimination power among different types of 2HDMs. We find that the pair production of the non-SM Higgs bosons via the universal gauge interactions is the dominant mechanism once above the kinematic threshold. Single Higgs boson production associated with a pair of heavy fermions could be important in the parameter region with enhanced Yukawa couplings. For both signal final states, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ annihilation channels dominate over the vector boson fusion (VBF) processes, except at high center of mass energies where the VBF processes receive large logarithmic enhancement with the increase of energies. Single Higgs boson $s$-channel production in ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$-annihilation via the radiative return can also be important for the Type-L 2HDM in the very large $\mathrm{tan}\ensuremath{\beta}$ region, extending the kinematic reach of the heavy Higgs boson mass to the collider energy. Considering both the production and decay of non-SM Higgs bosons, signals can be identified over the Standard Model backgrounds. With the pair production channels via annihilation, 95% C.L. exclusion reaches in the Higgs mass up to the production mass threshold of $\sqrt{s}/2$ are possible when channels with different final states are combined. Including single production modes can extended the reach further. Different types of 2HDMs can be distinguishable for moderate and large values of $\mathrm{tan}\ensuremath{\beta}$.

Search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector boson pairs in proton\u2013proton collisions at sqrt{s} = 13,{text {TeV}}

A search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector bosons, using proton–proton collisions at sqrt{s}=13,{text {TeV}} at the LHC, is reported. The data sample corresponds to an integrated luminosity of 137,{text {fb}}^{-1} collected with the CMS detector. Events are selected by requiring two or three electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass. No excess of events with respect to the standard model background predictions is observed. Model independent upper limits at 95% confidence level are reported on the product of the cross section and branching fraction for vector boson fusion production of charged Higgs bosons as a function of mass, from 200 to 3000,{text {GeV}}. The results are interpreted in the context of the Georgi–Machacek model.

Probing axionlike particles with γγ final states from vector boson fusion processes at the LHC

We perform a feasibility study to search for axionlike particles (ALPs) using vector boson fusion (VBF) processes at the LHC. We work in an effective field theory framework with a cutoff scale $\mathrm{\ensuremath{\Lambda}}$ and ALP mass ${m}_{a}$, and assume that ALPs couple to photons with strength $\ensuremath{\propto}1/\mathrm{\ensuremath{\Lambda}}$. Assuming proton-proton collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$, we present the total VBF ALP production cross sections, ALP decay widths and lifetimes, and relevant kinematic distributions as a function of ${m}_{a}$ and $\mathrm{\ensuremath{\Lambda}}$. We consider the $a\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ decay mode to show that the requirement of an energetic diphoton pair combined with two forward jets with large dijet mass and pseudorapidity separation can significantly reduce the Standard Model backgrounds, leading to a $5\ensuremath{\sigma}$ discovery reach for $10\text{ }\text{ }\mathrm{MeV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{TeV}$ with $\mathrm{\ensuremath{\Lambda}}\ensuremath{\lesssim}2\text{ }\text{ }\mathrm{TeV}$, assuming an integrated luminosity of $3000\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. In particular, this extends the LHC sensitivity to a previously unstudied region of the ALP parameter space.

Highly boosted Higgs bosons and unitarity in vector-boson fusion at future hadron colliders

We study the observability of new interactions which modify Higgs-pair production via vector-boson fusion processes at the LHC and at future proton-proton colliders. In an effective-Lagrangian approach, we explore in particular the effect of the operator {h}^2{W}_{mu nu}^a{W}^{a,mu nu} , which describes the interaction of the Higgs boson with transverse vector-boson polarization modes. By tagging highly boosted Higgs bosons in the final state, we determine projected bounds for the coefficient of this operator at the LHC and at a future 27 TeV or 100 TeV collider. Taking into account unitarity constraints, we estimate the new-physics discovery potential of Higgs pair production in this channel.

Search for nonresonant Higgs boson pair production in final states with two bottom quarks and two photons in proton-proton collisions at sqrt{s} = 13 TeV

A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of sqrt{s} = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into gamma gamma mathrm{b}overline{mathrm{b}} . The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κλ and the coupling between a pair of Higgs bosons and a pair of vector bosons c2V are constrained within the ranges −3.3 < κλ< 8.5 and −1.3 < c2V< 3.5 at 95% confidence level. Constraints on κλ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κλ and the top quark Yukawa coupling modifier κt.

Search for Higgs boson production in association with a high-energy photon via vector-boson fusion with decay into bottom quark pairs at sqrt{s} = 13 TeV with the ATLAS detector

A search is presented for the production of the Standard Model Higgs boson in association with a high-energy photon. With a focus on the vector-boson fusion process and the dominant Higgs boson decay into b-quark pairs, the search benefits from a large reduction of multijet background compared to more inclusive searches. Results are reported from the analysis of 132 fb−1 of pp collision data at sqrt{s} = 13 TeV collected with the ATLAS detector at the LHC. The measured Higgs boson signal yield in this final-state signature is 1.3 ± 1.0 times the Standard Model prediction. The observed significance of the Higgs boson signal above the background is 1.3 standard deviations, compared to an expected significance of 1.0 standard deviations.

Prospect of the search for $${\mathrm {W}}^{\prime }$$ in vector boson fusion at the high-luminosity large hadron collider

A search for a new heavy charged gauge boson $${\mathrm {W}}^{\prime }$$ produced via a vector boson fusion process with two hard jets in pp collisions in the high-luminosity Large hadron collider (HL-LHC) environment is presented. The HL-LHC will increase the peak instantaneous luminosity to $$7.5 \times 10^{34}~{\mathrm {cm}}^{-2}~{\mathrm {s}}^{-1}$$ and the center of mass energy of 14 TeV to collect integrated luminosities up to 3 $${\mathrm {ab}}^{-1}$$ , which will significantly improve sensitivity for the observation of new heavy particles via rare processes. In this paper, to investigate the signal sensitivity for a $${\mathrm {W}}^{\prime }$$ we use the heavy vector triplet model, in the context of a simplified phenomenological approach, under Monte-Carlo simulations. The search targets events with one energetic electron and large missing transverse momentum, as well as two jets with a large separation in pseudorapidity. The expected upper limit for the mass of $${\mathrm {W}}^{\prime }$$ and exclusion limit contour on coupling parameters are presented at the 95% confidence level for an integrated luminosity of 3 $${\mathrm {ab}}^{-1}$$ .