Search For Heavy Higgs Bosons Research Articles

Heavy Higgs boson searches at the LHC in light of a left-right symmetric model

Heavy Higgs boson searches at the LHC in light of a left-right symmetric model

Search for heavy Higgs bosons with flavour-violating couplings in multi-lepton plus b-jets final states in pp collisions at 13 TeV with the ATLAS detector

A search for new heavy scalars with flavour-violating decays in final states with multiple leptons and b-tagged jets is presented. The results are interpreted in terms of a general two-Higgs-doublet model involving an additional scalar with couplings to the top-quark and the three up-type quarks (ρtt, ρtc, and ρtu). The targeted signals lead to final states with either a same-sign top-quark pair, three top-quarks, or four top-quarks. The search is based on a data sample of proton-proton 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 recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are categorised depending on the multiplicity of light charged leptons (electrons or muons), total lepton charge, and a deep-neural-network output to enhance the purity of each of the signals. Masses of an additional scalar boson mH between 200 − 630 GeV with couplings ρtt = 0.4, ρtc = 0.2, and ρtu = 0.2 are excluded at 95% confidence level. Additional interpretations are provided in models of R-parity violating supersymmetry, motivated by the recent flavour and (g − 2)μ anomalies.

A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton–proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb−1. The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson’s mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.

Searches for Heavy Higgs Bosons in the Framework of 2HDM Model

Searches for Heavy Higgs Bosons in the Framework of 2HDM Model

A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at [formula omitted] with the ATLAS detector

A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at [formula omitted] with the ATLAS detector

Flavor and CP-violating Higgs sector in two Higgs doublet models with $$U(1)'$$

We investigate the role of a local $U(1)'$ symmetry for the problem of CP violation in the effective theory for two Higgs doublet models and its microscopic counterparts. First, in two Higgs doublet models with $U(1)'$, we show that the higher-dimensional operators in the scalar potential violate the CP symmetry with an interplay with the mixing mass parameter, giving rise to small mixings between CP-even and CP-odd scalars. Motivated by the $B$-meson anomalies in recent years, we take the flavored $U(1)'$ to be a benchmark model for specifying the flavor structure. Then, we calculate the electric dipole moment of electron (eEDM) at two loops due to the CP-violating higher-dimensional operators and identify the correlation between the masses of heavy Higgs bosons and the cutoff scale from the bound on eEDM. We also comment on the possibility of making an independent test of the CP violation in the collider searches for heavy Higgs bosons. Finally, we show how the obtained eEDM results in the effective theory can be used to constrain microscopic models with an explicit CP violation in the partially decoupled or dark sectors.

Probing electroweak baryogenesis induced by extra bottom Yukawa coupling via EDMs and collider signatures

We study the prospect of probing electroweak baryogenesis driven by an extra bottom Yukawa coupling ρbb in a general two Higgs doublet model via electric dipole moment (EDM) measurements and at the collider experiments. The parameter space receives meaningful constraints from 125 GeV Higgs h boson signal strength measurements as well as several heavy Higgs boson searches at the Large Hadron Collider (LHC). In addition, we show that the asymmetry of the CP asymmetry of inclusive B → Xsγ decay would provide complementary probe. A discovery is possible at the LHC via bg → bA → bZh process if |ρbb| ∼ 0.15 and 250 GeV≲ mA ≲ 350 GeV, where A is CP odd scalar. For mA> 2mt threshold, where mt is the top quark mass, one may also discover bg → bA → btoverline{t} at the high luminosity LHC run if an extra top Yukawa coupling |ρtt| ∼ 0.5, though it may suffer from systematic uncertainties. For completeness we study gg → toverline{t}A → toverline{t}boverline{b} but find it not promising.

The second Higgs at the lifetime frontier

We assess the current coverage and the future discovery potential of LHC searches for heavy Higgs bosons decaying into long-lived particles (LLPs), focusing primarily on the production of pairs of LLPs with hadronic final states. These signatures are generic in dark sectors where a heavy scalar decays into pairs of lighter states which subsequently mix with the Standard Model Higgs. We show that a handful of existing analyses provide broad coverage of LLP decay lengths ranging from millimeters to tens of meters, and explore the complementarity between searches for displaced and prompt final states in several simplified models. For both heavy singlet and heavy doublet scalars, LLP searches typically provide the leading sensitivity in current data and exhibit the strongest discovery potential in future LHC runs. We further translate the impact of these searches into the parameter space of various Twin Higgs models, demonstrating that LLP searches are a promising avenue for discovering a Twin Higgs with displaced decays. Finally, we propose a variety of additional search channels that would improve coverage of the second Higgs at the lifetime frontier.

Further study of the global minimum constraint on the two-Higgs-doublet models: LHC searches for heavy Higgs bosons

The usually considered vacuum of the two-Higgs-doublet model (2HDM) could be unstable if it locates at a local but not global minimum (GM) of the scalar potential. By requiring the vacuum to be a GM, we obtain an additional constraint, namely the GM constraint, on the scalar potential. In this work, we explore the GM constraint on the $CP$-conserving general 2HDM. This constraint is found to put limits on the soft $\mathbb{Z}_2$ breaking mass parameter $m_{12}^2$ and also squeeze the heavy $CP$-even Higgs boson mass into larger values for the $m_{12}^2< 0$ case. Combined with the current global signal fits from the LHC measurements of the 125 GeV Higgs boson, we discuss the phenomenological implications for the heavy Higgs boson searches at the LHC.

Searching for heavy Higgs bosons in the toverline{t}Z and tbW final states

In the context of two-Higgs doublet models, we explore the possibility of searching for heavy Higgs bosons in the toverline{t}Z and tbW final states. We develop realistic analysis strategies and in the case of the toverline{t}Z channel provide a detailed evaluation of the new-physics reach at the 14 TeV LHC. We find that already with an integrated luminosity of 300 fb−1 searches for the toverline{t}Z signature can provide statistically significant constraints at low values of tan β for heavy Higgs masses in the range from around 450 GeV to 1150 GeV. Future searches for heavy Higgses in the tbW final state are also expected to be able to probe parts of this parameter space, though the precise constraints turn out to depend sensitively on the assumed systematics on the shape of the toverline{t} background.

Search strategies for pair production of heavy Higgs bosons decaying invisibly at the LHC

The search for heavy Higgs bosons at the LHC represents an intense experimental program, carried out by the ATLAS and CMS collaborations, which includes the hunt for invisible Higgs decays and dark matter candidates. No significant deviations from the SM backgrounds have been observed in any of these searches, imposing significant constraints on the parameter space of different new physics models with an extended Higgs sector. Here we discuss an alternative search strategy for heavy Higgs bosons decaying invisibly at the LHC, focusing on the pair production of a heavy scalar H together with a pseudoscalar A, through the production mode qq¯→Z⁎→HA. We identify as the most promising signal the final state made up of 4b+ETmiss, coming from the heavy scalar decay mode H→hh→bb¯bb¯, with h being the discovered SM-like Higgs boson with mh=125GeV, together with the invisible channel of the pseudoscalar. We work within the context of simplified MSSM scenarios that contain quite heavy sfermions of most types with O(10)TeV masses, while the stops are heavy enough to reproduce the 125 GeV mass for the lightest SM-like Higgs boson. By contrast, the gauginos/higgsinos and the heavy MSSM Higgs bosons have masses near the EW scale. Our search strategies, for a LHC center-of-mass energy of s=14TeV, allow us to obtain statistical significances of the signal over the SM backgrounds with values up to ∼1.6σ and ∼3σ, for total integrated luminosities of 300fb−1 and 1000fb−1, respectively.

Search for Heavy Higgs Bosons in Fermionic Decay Channels with CMS

Latest results of searches for heavy Higgs bosons in fermionic final states are presented using the CMS detector at the LHC. Results are based on pp collision data collected at centre-of-mass energies of 8 and 13 TeV which have been interpreted according to different extensions of the Standard Model such as MSSM, 2HDM, and NMSSM. These searches look for evidence of other scalar or pseudoscalar bosons, in addition to the observed SM-like 125 GeV Higgs boson, and set 95% confidence level upper limits in fermionic final states and benchmark models explored. The talk reviews briefly the major results obtained by the CMS Collaboration during Run I, and presents the most recent searches performed during Run II.

Search for Heavy Higgs Bosons with the ATLAS Detector

The ATLAS experiment at the Large Hadron Collider performed searches for heavy Higgs bosons, whose presence would establish the existance of new physics. Searches for charged and neutral Higgs bosons are carried out using 8 or 13 TeV data for various production modes and in many different final states. No deviations from Standard Model expectations are observed. Exclusions limits are set on the production cross section and on parameters in various benchmark models.

Higgs pair production in the CP-violating two-Higgs-doublet model

The SM-like Higgs pair production is discussed in the framework of the general CP-violating two-Higgs-doublet model, where we find that the CP-violating mixing angles can be related to the Higgs self-couplings. Therefore, the future experimental searches for Higgs boson pairs can be constrained by the improved precision of the electric dipole moment measurements. Based on a series of constraints of the SM-like Higgs boson signal fits, the perturbative unitarity and stability bounds to the Higgs potential, and the most recent LHC searches for heavy Higgs bosons, we suggest a set of benchmark models for the future high-energy collider searches for Higgs pair production. The [Formula: see text] colliders operating at [Formula: see text] are capable of measuring the Higgs cubic self-couplings of the benchmark models directly. We also estimate the cross sections of the resonance contributions to the Higgs pair productions for the benchmark models at the future LHC and SppC/FCC-hh runs.

ATLAS searches for heavy Higgs bosons and supersymmetry using tau decays

Results from the ATLAS experiment from searches for heavy Higgs bosons and supersymmetry with tau leptons in the final states are presented. The analyses discussed use datasets corresponding to approximately 13-15 fb−1 of 13 TeV proton-proton collision data taken in the years 2015-2016. No significant excess above the Standard Model is observed, and limits are set on new physics in various supersymmetric scenarios.

Searches for high mass Higgs bosons with the ATLAS detector

Recent results from searches for heavy Higgs bosons, using the ATLAS detector at the CERN LHC are presented. The searches use proton–proton collision data collected during the second running period of the LHC (LHC Run-II), at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 3.2 fb−1. The results are interpreted in a range of scenarios, including theories beyond the Standard Model of particle physics, and extend the upper limits set during LHC Run-I toward higher mass regions.

Higgs boson physics and broken flavor symmetry – LHC phenomenology

The LHC implications are presented of a simplified model of broken flavor symmetry in which a new scalar (a flavon) emerges with mass in the TeV range. We summarize the influence of the model on Higgs boson physics, notably on the production cross section and decay branching fractions. Limits are obtained on the flavon ϕ from heavy Higgs boson searches at the LHC at 7 and 8 TeV. The branching fractions of the flavon are computed as a function of the flavon mass and the Higgs-flavon mixing angle. We explore possible discovery of the flavon at 14 TeV, particularly via the ϕ→Z0Z0 decay channel in the 2ℓ2ℓ′ final state, and through standard model Higgs boson pair production ϕ→hh in the bb‾γγ final state. The flavon mass range up to 500 GeV could probed down to quite small values of the Higgs-flavon mixing angle with 100 fb−1 of integrated luminosity at 14 TeV.

Interference contributions to gluon initiated heavy Higgs production in the two-Higgs-doublet model

We discuss the production of a heavy neutral Higgs boson of a CP-conserving Two-Higgs-Doublet Model in gluon fusion and its decay into a four-fermion final state, $gg (\rightarrow VV) \rightarrow e^+e^-\mu^+\mu^-/e^+e^-\nu_l\bar\nu_l$. We investigate the interference contributions to invariant mass distributions of the four-fermion final state and other relevant kinematical observables. The relative importance of the different contributions is quantified for the process in the on-shell approximation, $gg\rightarrow ZZ$. We show that interferences of the heavy Higgs with the light Higgs boson and background contributions are essential for a correct description of the differential cross section. Even though they contribute below $\mathcal{O}(10\%)$ to those heavy Higgs signal cross sections, to which the experiments at the Large Hadron Collider were sensitive in its first run, we find that they are sizeable in certain regions of the parameter space that are relevant for future heavy Higgs boson searches. In fact, the interference contributions can significantly enhance the experimental sensitivity to the heavy Higgs boson.

Constraints on new phenomena via Higgs boson couplings and invisible decays with the ATLAS detector

The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=7$ TeV and 20.3 fb$^{-1}$ at $\sqrt{s}=8$ TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the $\gamma\gamma$, $ZZ$, $WW$, $Z\gamma$, $bb$, $\tau\tau$, and $\mu\mu$ decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the $\gamma\gamma$ and $ZZ$ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of $m_{A}>370$ GeV in the "hMSSM" simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with $W/Z$ ($Z\to ll$, $W/Z \to jj$) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter.

Complementarity of LHC and EDMs for exploring Higgs CP violation

We analyze the constraints on a CP-violating, flavor conserving, two Higgs doublet model from the measurements of Higgs properties and from the search for heavy Higgs bosons at LHC, and show that the stronger limits typically come from the heavy Higgs search channels. The limits on CP violation arising from the Higgs sector measurements are complementary to those from EDM measurements. Combining all current constraints from low energy to colliders, we set generic upper bounds on the CP violating angle which parametrizes the CP odd component in the 126 GeV Higgs boson.