Higgs Boson Research Articles

Search for light long-lived particles decaying to displaced jets in proton-proton collisions at √s = 13.6 TeV.

A search for light long-lived particles decaying to displaced jets is presented, using a data sample of proton-proton collisions at a center-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 34.7 fb$^{-1}$, collected with the CMS detector at the CERN LHC in 2022. Novel trigger, reconstruction, and machine-learning techniques were developed for and employed in this search. After all selections, the observations are consistent with the background predictions. Limits are presented on the branching fraction of the Higgs boson to long-lived particles that subsequently decay to quark pairs or tau lepton pairs. An improvement by up to a factor of 10 is achieved over previous limits for models with long-lived particle masses smaller than 60 GeV and proper decay lengths smaller than 1 m. The first constraints are placed on the fraternal twin Higgs and folded supersymmetry models, where the lower bounds on the top quark partner mass reach up to 350 GeV for the fraternal twin Higgs model and 250 GeV for the folded supersymmetry model.

Production of single doubly charged Higgs bosons at muon colliders

Production of single doubly charged Higgs bosons at muon colliders

Search for diphoton resonances in the 66 to 110 GeV mass range using pp collisions at s = 13 TeV with the ATLAS detector

A search is performed for light, spin-0 bosons decaying into two photons in the 66 to 110 GeV mass range, using 140 fb−1 of proton-proton collisions at s = 13 TeV produced by the Large Hadron Collider and collected by the ATLAS detector. Multivariate analysis techniques are used to define event categories that improve the sensitivity to new resonances beyond the Standard Model. A model-independent search for a generic spin-0 particle and a model-dependent search for an additional low-mass Higgs boson are performed in the diphoton invariant mass spectrum. No significant excess is observed in either search. Mass-dependent upper limits at the 95% confidence level are set in the model-independent scenario on the fiducial cross-section times branching ratio into two photons in the range of 8 fb to 53 fb. Similarly, in the model-dependent scenario upper limits are set on the total cross-section times branching ratio into two photons as a function of the Higgs boson mass in the range of 19 fb to 102 fb.

Muon (g − 2) and thermal WIMP DM in U1Lμ−Lτ models

The U1Lμ−Lτ model is anomaly-free with the Standard Model (SM) fermion content, and can make substantial contributions to the muon (g − 2) at the level of ∆aμ ∼ O(10) × 10−10 for MZ′ ∼ O(10 − 100) MeV and gX ∼ (4 − 8) × 10−4. In this light Z′ region, it was claimed that the model can also incorporate thermal WIMP dark matter (DM) if MDM ∼ MZ′/2. This setup relies on DM particles annihilating into SM particles through a Z′-mediated s-channel. In this work, we show that this tight relationship between MZ′ and MDM can be evaded or nullified both for scalar and spin-1/2 DM by considering the contributions from the dark Higgs boson (H1). The dark Higgs boson plays an important role, not only because it gives mass to the dark photon but also because it introduces additional DM annihilation channels, including new final states such as H1H1, Z′Z′, and Z′H1. As a result, the model does not require a close mass correlation between the Z′ boson and dark matter MDM ~ MZ′/2 any longer, allowing for a broader range of mass possibilities for both scalar and fermionic dark matter types. We explore in great details various scenarios where the U(1) symmetry is either fully broken or partially remains as discrete symmetries, Z2 or Z3. This approach broadens the model’s capacity to accommodate various WIMP dark matter phenomena in the light Z′ region where the muon (g − 2)μ makes a sensitive probe of the model.

Search for bottom quark associated production of the standard model Higgs boson in final states with leptons in proton-proton collisions at [formula omitted]

This Letter presents the first search for bottom quark associated production of the standard model Higgs boson, in final states with leptons. Higgs boson decays to pairs of tau leptons and pairs of leptonically decaying W bosons are considered. The search is performed using data collected from 2016 to 2018 by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138fb−1. Upper limits at the 95% confidence level are placed on the signal strength for Higgs boson production in association with bottom quarks; the observed (expected) upper limit is 3.7 (6.1) times the standard model prediction.

Light Dark Fermion in Two Natural Scenarios

Dark matter is postulated as a light fermion in two natural scenarios as the outcome of a softly broken discrete symmetry. It is produced from the naturally suppressed decay of the standard-model Higgs boson through the freeze-in mechanism.

95 GeV Higgs boson and spontaneous CP -violation at the finite temperature

The ATLAS and CMS collaborations reported a diphoton excess in the invariant mass distribution around the 95.4 GeV with a local significance of 3.1σ. Moreover, there is another 2.3σ local excess in the bb¯ final state at large electron-positron collider in the same mass region. A plausible solution is that the Higgs sector is extended to include an additional Higgs boson with a mass of 95.4 GeV. We study a complex singlet scalar extension of the two-Higgs-doublet model in which the 95.4 GeV Higgs is from the mixing of three CP-even Higgs fields. In addition, the extended Higgs potential can achieve spontaneous CP-violation at the finite temperature and restore CP symmetry at the present temperature of the Universe. We find that the model can simultaneously explain the baryon asymmetry of the Universe, the diphoton and bb¯ excesses around the 95.4 GeV while satisfying various relevant constraints including the experiments of collider and electric dipole moment. Published by the American Physical Society 2024

Unified interpretation of the muon g−2 anomaly, the 95 GeV diphoton, and bb¯ excesses in the general next-to-minimal supersymmetric standard model

We investigate three intriguing anomalies within the framework of the general next-to-minimal supersymmetric standard model. These anomalies include a significant deviation of the experimental results for the muon anomalous magnetic moment from its standard model prediction, with a confidence level of 5.1σ; a joint observation by the CMS and ATLAS Collaborations of a diphoton excess with a local significance of 3.1σ in the invariant mass distribution around 95.4 GeV; and a reported excess in the bb¯ production at the Large Electron-Positron Collider with a local significance of 2.3σ. Through analytical and numerical analyses, we provide unified interpretations across an extensive parameter space that remain consistent with current experimental restrictions from data on the Higgs boson at 125 GeV, B-physics measurements, and dark matter observables, as well as existing searches for supersymmetry and extra Higgs bosons. We attribute the muon anomaly to loops involving muon-smuon-neutralino and muon-sneutrino-chargino interactions, while attributing the diphoton and bb¯ excesses to the resonant production of a singlet-dominated scalar. These proposed solutions are poised for experimental tests at the high-luminosity LHC and future linear colliders. Published by the American Physical Society 2024

Higgs boson production at μ+μ+ colliders

We study Higgs boson production at μ+μ+ colliders at high energy. Since both initial-state particles are positively charged, there is no W boson fusion at the leading order, as it requires a W+W− pair. However, we find that the cross section of the higher-order, γ-and Z-mediated W boson fusion process is large at high center-of-mass energies s, growing as (logs)3. This is in contrast to the logs behavior of the leading-order W boson fusion. Thus, even though it is a higher-order process, the rate of Higgs boson production for 10 TeV energies at μ+μ+ colliders with polarized beams can be as high as about half of the one at μ+μ− colliders, assuming the same integrated luminosity. To calculate the cross section of this process accurately, we carefully treat the collinear emission of the photon in the intermediate state. The thereby obtained large cross section furthermore shows the significance of Higgs production with an extra W boson in the final state also at μ+μ− and e+e− colliders. Published by the American Physical Society 2024

Fermion masses, neutrino mixing and Higgs-mediated flavor violation in 3HDM with S3 permutation symmetry

The Yukawa and scalar sectors of a general S3-symmetric three-Higgs doublet model (3HDM) are investigated. The Yukawa interactions are constructed in an S3-invariant way, while the scalar potential contains S3 soft-breaking terms. Global fits to the quark/lepton masses and CKM/PMNS matrices are performed. Excellent fits to all fermion mass and mixing parameters are obtained. Both normal ordering and inverted ordering of neutrino masses are found to be admissible within the framework, with a prediction for the CP-violation phase, δCP ≃ 120°. The fit results in the Yukawa sector are further investigated, together with the scalar sector, imposing constraints from Higgs-mediated neutral meson mixing and neutron electric dipole moment (EDM). We explore the lowest allowed mass of the heavy Higgs bosons, consistent with these constraints, and find it to be about 17 TeV. The corresponding neutron EDM is around 1.7 × 10−27 e-cm, which is within reach of proposed experiments. It is found that the constraints from the K-meson system dominate, while those from the D meson system are marginal.

Lepton flavor-violating Higgs decays mediated by ultralight gauge boson

We present an analysis of the lepton-flavor violating decay of the Higgs boson mediated by an ultralight gauge boson, χ. Our analysis matches a model generating the lepton flavor-violating interaction ℓ¯iℓjχ at tree level with an effective field theory, safeguarding a physical massless χ-boson limit of the observables. By utilizing the upper bounds on H→ℓiℓ¯j decays from CMS and ATLAS Collaborations, we establish an indirect upper limit on the nonstandard decay H→ℓiℓ¯jχ. The analysis encompasses various observables such as the lepton energy spectrum, Dalitz plot distribution, and Lepton Charge and Forward-Backward Asymmetries.

Probing Heavy Charged Higgs Boson Using Multivariate Technique at Gamma-Gamma Collider

Abstract he current study explores the production of charged Higgs particles through photon-photon collisions
within the context of the Two Higgs Doublet Model, including one-loop-level scattering amplitudes of
Electroweak and QED radiation. The cross-section has been scanned for plane (mϕ0 , √s) investigating
the process of γγ → H+H−. Three particular numerical scenarios i.e., low-mH , non-alignment, and short-
cascade are employed. The decay channels for charged Higgs particles are examined using h0 for low-mH0
and H0 for non-alignment and short-cascade scenario incorporating the new experimental and theoretical
constraints along with the analysis for cross-sections. It reveals that at low energy, it is consistently higher
for all scenarios. However, as √s increases, it reaches a peak value at 1 TeV for all benchmark scenarios.
The branching ratio of the decay channels indicates that for non-alignment, the mode of decay W ±h0 takes
control, and for short cascade, the prominent decay mode remains t¯b, while in the low-mH the dominant
decay channel is of W ±h0. In our research, we employ contemporary machine-learning methodologies
to investigate the production of high energy Higgs bosons within a 3.0 TeV γγ collider. We have used
multivariate approaches such as Boosted Decision Trees (BDT), LikelihoodD, and Multilayer Perceptron
(MLP) to show the observability of heavy-charged Higgs Bosons versus the most significant Standard Model
backgrounds. The purity of the signal efficiency and background rejection are measured for each cut value.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd

Dispersive determination of the fourth generation lepton masses

Abstract We continue our previous determination of the masses of the sequential fourth generation quarks in an extension of the Standard Model, and predict the mass m_4 (m_L) of the fourth generation neutrino \nu_4 (charged lepton L) by solving the dispersion relations associated with heavy fermion decays. The results m_4\approx 170 GeV and m_L\approx 270 GeV are extracted from the dispersive analyses of the t -> d e^+ \nu_4 and L^- -> \nu_1 t̄ d decay widths, respectively, where t (d, e^+, \nu_1) denotes a top quark (down quark, positron, light neutrino). The predictions are cross-checked by examining the L^- -> \nu_4 ū d decay, ū being an anti-up quark. It is shown that the fourth generation leptons with the above masses survive the current experimental bounds from Higgs boson decays into photon pairs and from the oblique parameters. We also revisit how the existence of the fourth generation leptons impacts the dispersive constraints on the neutrino masses and the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix elements. It is found that the unitarity of the 3×3 PMNS matrix holds well up to corrections of O(m_\nu^2/m_W^2 ), m_\nu (m_W ) being a light neutrino (the W boson) mass, whose mixing angles and CP phase prefer the values θ_{12}\approx 34^\circ, θ_{23}\approx 47^\circ, θ_{13}\approx 5^\circ and δ\approx 200^\circ in the normal-ordering scenario for neutrino masses.

95 GeV excesses in the Z3 -symmetric next-to-minimal supersymmetric standard model

Recent analyses by CMS and ATLAS suggest a deviation in the diphoton channel at approximately 95 GeV, alongside a previously observed excess in bb¯ signals at a similar mass by the Large Electron-Positron collider, potentially hinting at a new scalar particle. This study explores this possibility within the framework of the Z3-symmetric next-to-minimal supersymmetric standard model. A comprehensive parameter scan was conducted, integrating constraints from dark matter relic density, direct detection experiments, and the properties of the observed 125 GeV Higgs boson. The results demonstrate that the model can accommodate the observed excesses with a singlet-dominated CP-even scalar boson near 95 GeV. The model accurately predicts signal strengths of the diphoton and bb¯ channels at a level of 1σ. Furthermore, it accounts for the measured dark matter relic abundance through bino-dominated neutralinos coannihilation with winolike electroweakinos, all while remaining consistent with existing Large Hadron Collider (LHC) constraints. These findings pave the way for future validation at the high-luminosity LHC and linear colliders, which may offer crucial tests of the model’s predictions. Published by the American Physical Society 2024

Extending hh→bb̄bb̄ searches into the HL-LHC era

Searches for pairs of Higgs bosons are the best tools to precisely measure the Higgs boson self-coupling [Formula: see text] in future colliders. We study various strategies for the [Formula: see text] search in the HL-LHC era with focus on constraining [Formula: see text]. We implement a machine-learning-based approach to separate signal and background and apply recent advances in machine learning interpretability, compare the traditional 4 b-jet reconstruction to final states with 1 or 2 large-radius jets, and test scenarios with different top-quark Yukawa couplings, among other factors. This talk was presented as part of the Mini-workshop on Machine Learning at the 10th International Conference on New Frontiers in Physics (ICNFP-2021). a

Theory Of Everything: A Conceptual Synthesis Of An Eleven Dimensional Dynamic Hyperspace As A Unified Zeropoint Subspace Ether

This theoretical research paper aims to aid the conceptual evolution of Grand Unified Theory (GUT), through developing the qualitative alignment of current divergent theoretical perspectives and outlier experimental evidence in the novel synthesis of a holistic new perspective through the philosophy of science context of initiating a paradigm shift in the dynamics of modern particle and dimensional physics theory. Taking the central components of Superstring and M-theory into a conceptual synthesis of theoretical dynamics and experimental evidence incorporating the four fundamental forces of nature, hyperspace theory, zero-point vacuum fluctuations of energy, the Casimir virtual particle effect, the higgs field, photoelectric radiation, quantum tunnelling, dark energy and the four dimensions of space and time in the conceptual composition of a schematic alignment of dynamic essences of physical existence formed into an eleven-dimensional subspace unification of manifest reality. Exploring the theoretical interaction of three polemics of opposed dimensional properties and essences to realities manifest nature, as intersecting dichotomously distinct and conceptually defined axis of hyperspatial essence unified through a zeropoint subspace ether of seven dimensions, an eleven dimensional theory of reality incorporating the aforementioned components as the end product is synthesised. With the desire of elaborating and expanding the qualitative and conceptual dynamics of Grand Unified Theory as a paradigm, this research paper hopes to develop a broadened theoretical context along with increasing the alignment precision and dynamic inclusivity of current divergent tangents and experimental outliers into the synthesis of a complete and comprehensive future GUT paradigm.

Improved constraints on Higgs boson self-couplings with quartic and cubic power dependencies in the cross section

Abstract The precise determination of the Higgs boson self-couplings is essential for understanding the mechanism behind electroweak symmetry breaking. However, due to the limited number of Higgs boson pair events at the LHC, only loose constraints have been established so far. 
Current constraints are based on the assumption that the cross section is a quadratic function of the trilinear Higgs self-coupling within the $\kappa$ framework. Incorporating higher-order quantum corrections from virtual Higgs bosons would significantly alter this function form, introducing new quartic and cubic power dependencies on the trilinear Higgs self-coupling. 
To derive this new function form, we propose a specialized renormalization procedure that tracks all Higgs self-couplings at each calculation step. 
Additionally, we introduce renormalization constants for the coupling modifiers within the $\kappa$ framework to ensure the cancellation of all ultraviolet divergences.
With the new function forms of the cross sections in both the gluon-gluon fusion and vector boson fusion channels,
the upper limit of $\kappa_{\lambda_{\rm 3H}}=\lambda_{\rm 3H}/\lambda_{\rm 3H}^{\rm SM}$ by the ATLAS (CMS) collaboration is reduced from 6.6 (6.49) to 5.4 (5.37).
However, extracting a meaningful constraint on the quartic Higgs self-coupling $\lambda_{\rm 4H}$ from Higgs boson pair production data remains challenging.
We also present the invariant mass distributions of the Higgs boson pair at different values of $\kappa_{\lambda}$, which could aid in setting optimal cuts for experimental analysis.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Nonlinear gauge-Higgs CP violation

A critical element of the LHC physics program is the search for an additional source of CP violation. This is largely unexplored in the context of nonlinear Higgs physics, which is naturally described in Higgs effective field theory (HEFT). Relevant new higher-dimensional operators modify the production rate and branching ratios of the Higgs boson, decorrelating different Higgs multiplicities. In this work, we consider single Higgs and Higgs pair production via weak boson fusion from the perspective of gauge-Higgs CP violation through the lens of Higgs nonlinearity. This generalizes existing rate-based searches and analyses by the ATLAS and CMS experiments. Particular focus is given to the phenomenological differences in the expected beyond Standard Model (BSM) sensitivity pattern when comparing HEFT constraints with Standard Model effective field theory (SMEFT) limits. Published by the American Physical Society 2024

Triboson production in the SMEFT

We study the production of three electroweak gauge bosons at the LHC, in the effective field theory of the standard model, at dimension six and next-to-leading order in QCD. We present results for inclusive cross-sections and differential distributions, finding that these QCD corrections are large, often vary across the phase-space and notably differ from those observed in the standard model. We then explore the potential of the recently observed triboson production processes for improving the sensitivity brought by electroweak precision observables and diboson data. The additional sensitivity we observe is dominated by resonant Higgs boson contributions, with decays to photon pairs in particular. A global analysis including Higgs boson data is therefore needed for a fair assessment of the future reach of triboson measurements on heavy new physics.

Spectral data of special orthogonal Higgs bundles and Hecke modification

ABSTRACT We give a complete, self-contained computation of the spectral data parametrizing Higgs bundles in the generic fibres of $\mathrm{SO}_{2n+1}$-Hitchin fibration where the Higgs fields are L-twisted endomorphisms. Although the spectral data are known in the literature, we develop a new approach, which takes advantage of Hecke modification. Furthermore, we present the computation for $\mathrm{Sp}_{2n}$ and $\mathrm{SO}_{2n}$ cases while clarifying some aspects of the correspondence, which are not well explained in the pre-existing literature. We also compute the number of connected components of the generic fibres and demonstrate Langlands duality in the fibres via the canonical duality in the fibres.