Pseudoscalar Higgs Boson Research Articles

Search for heavy neutral Higgs bosons decaying into a top quark pair in 140 fb−1 of proton-proton collision data 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

A search for heavy pseudo-scalar (A) and scalar (H) Higgs bosons decaying into a top-quark pair (tt¯\\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}) has been performed with 140 fb−1 of proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider 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. Interference effects between the signal process and Standard Model (SM) tt¯\\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} production are taken into account. Final states with exactly one or exactly two electrons or muons are considered. No significant deviation from the SM prediction is observed. The results of the search are interpreted in the context of a two-Higgs-doublet model (2HDM) of type II in the alignment limit with mass-degenerate pseudo-scalar and scalar Higgs bosons (mA = mH) and the hMSSM parameterisation of the minimal supersymmetric extension of the Standard Model. Ratios of the two vacuum expectation values, tan β, smaller than 3.49 (3.16) are excluded at 95% confidence level for mA = mH = 400 GeV in the 2HDM (hMSSM). Masses up to 1240 GeV are excluded for the lowest tested tan β value of 0.4 in the 2HDM. In the hMSSM, masses up to 950 GeV are excluded for tan β = 1.0. In addition, generic exclusion limits are derived separately for single scalar and pseudo-scalar states for different choices of their mass and total width.

Rapidity distribution of pseudoscalar Higgs boson to NNLOA+NNLL¯

We present the differential predictions for the rapidity distribution of pseudoscalar Higgs boson through gluon fusion at the LHC. These results are obtained taking into account the soft-virtual (SV) as well as the next-to-soft virtual (NSV) resummation effects to next-to-next-to-leading-logarithmic (NNLL¯) accuracy and matching them to the approximate fixed order next-to-next-to-leading-order (NNLOA) computation. We perform the resummation in two-dimensional Mellin space by limiting ourselves to the contributions only from gluon-gluon (gg) initiated channels. The NNLOA rapidity distribution of pseudoscalar Higgs is obtained by applying a ratio method on the NNLO rapidity distribution of the scalar Higgs boson. We also present the first analytical results of N3LO rapidity distribution of pseudoscalar Higgs at SV+NSV accuracy. The phenomenological impacts of NNLOA+NNLL¯ predictions for 13 TeV LHC are studied. We observe that for mA=125(700) GeV the SV+NSV resummation at the NNLL¯ level brings about 14.76% (11.48%) corrections to the NNLOA results at the central scale value of μR=μF=mA. Further, we find that the sensitivity to the renormalization scale gets improved substantially by the inclusion of NSV resummed predictions at NNLL¯ accuracy. Published by the American Physical Society 2024

A new LHC search for dark matter produced via heavy Higgs bosons using simplified models

Searches for dark matter produced via scalar resonances in final states consisting of Standard Model (SM) particles and missing transverse momentum are of high relevance at the LHC. Motivated by dark-matter portal models, most existing searches are optimized for unbalanced decay topologies for which the missing momentum recoils against the visible SM particles. In this work, we show that existing searches are also sensitive to a wider class of models, which we characterize by a recently presented simplified model framework. We point out that searches for models with a balanced decay topology can be further improved with more dedicated analysis strategies. For this study, we investigate the feasibility of a new search for bottom-quark associated neutral Higgs production with a boverline{b}Z+{p}_{textrm{T}}^{textrm{miss}} final state and perform a detailed collider analysis. Our projected results in the different simplified model topologies investigated here can be easily reinterpreted in a wide range of models of physics beyond the SM, which we explicitly demonstrate for the example of the Two-Higgs-Doublet model with an additional pseudoscalar Higgs boson.

Search for toverline{t}H/Ato toverline{t}toverline{t} production in the multilepton final state in proton–proton collisions at sqrt{s} = 13 TeV with the ATLAS detector

A search for a new heavy scalar or pseudo-scalar Higgs boson (H/A) produced in association with a pair of top quarks, with the Higgs boson decaying into a pair of top quarks (H/A → toverline{t} ) is reported. The search targets a final state with exactly two leptons with same-sign electric charges or at least three leptons. The analysed dataset corresponds to an integrated luminosity of 139 fb−1 of proton–proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Two multivariate classifiers are used to separate the signal from the background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of a type-II two-Higgs-doublet model. The observed (expected) upper limits at 95% confidence level on the toverline{t}H/A production cross-section times the branching ratio of H/A → toverline{t} range between 14 (10) fb and 6 (5) fb for a heavy Higgs boson with mass between 400 GeV and 1000 GeV, respectively. Assuming that only one particle, either the scalar H or the pseudo-scalar A, contributes to the toverline{t}toverline{t} final state, values of tan β below 1.2 or 0.5 are excluded for a mass of 400 GeV or 1000 GeV, respectively. These exclusion ranges increase to tan β below 1.6 or 0.6 when both particles are considered.

Investigation of (g-2)_{mu } anomaly in the mu -specific 2HDM with vector like leptons and the phenomenological implications

The anomalous magnetic moment of muons has been a long-standing problem in SM. The current deviation of experimental value of the (g-2)_{mu } from the standard model prediction is exactly 4.2sigma . Two Higgs Doublet Models can accommodate this discrepancy but such type of model naturally generate flavor changing neutral current(FCNC). To prevent this it was postulated that 2HDM without FCNC required that all fermions of a given charge couple to the same Higgs boson but the rule breaks in Muon Specific Two Higgs Doublet Model where all fermions except muon couple to one Higgs doublet and muon with the other Higgs doublet. The muon specific 2HDM provides an explanation for muon anomaly for extremely large tan beta with a particular value of m_{12}^2. As a result, the parameter space of m_{12}^2 drastically decreased for the muon anomaly solution. To evade the limitation of this model we have extended this model with a vector like lepton generation which could explain the muon anomaly at low tan beta value with a heavy pseudo scalar Higgs boson under the shadow of current experimental and theoretical constraints. Moreover, with the help of the cut based analysis and multivariate analysis methods, we have also attempted to shed some light on the potential experimental signature of vector lepton decay to the heavy Higgs boson in the LHC experiment. We have showed that a multivariate analysis can increase the vector like leptons signal significance even in the high VLL mass and low tan beta region than that of a cut based analysis.

Pseudoscalar MSSM Higgs Production at NLO SUSY-QCD

One of the most important mechanisms at the Large Hadron Collider (LHC) for the production of the pseudoscalar Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) is the loop-induced gluon fusion process gg → A. The higher-order QCD corrections have been obtained a long time ago and turned out to be large. However, the genuine supersymmetric (SUSY–)QCD corrections have been obtained only in the limit of large SUSY particle masses so far. We describe our calculation of the next-to-leading-order (NLO) SUSY-QCD results with full mass dependence and present numerical results for a few representative benchmark points. We also address the treatment of the effective top and bottom Yukawa couplings, in the case of heavy SUSY particles, in terms of effective low-energy theories where the heavy degrees of freedom have been decoupled. Furthermore, we include a discussion of the relation between the SUSY-QCD corrections that we have computed and the Adler-Bardeen theorem for the axial anomaly. In addition, we apply our results to the gluonic and photonic pseudoscalar Higgs decays A → gg, γγ at NLO.

FlexibleDecay: An automated calculator of scalar decay widths

We present FlexibleDecay, a tool to calculate decays of scalars in a broad class of BSM models. The tool aims for high precision particularly in the case of Higgs boson decays. In the case of scalar and pseudoscalar Higgs boson decays the known higher order SM QED, QCD and EW effects are taken into account where possible. The program works in a modified MS‾ scheme that exhibits a decoupling property with respect to heavy BSM physics, with BSM parameters themselves treated in the MS‾/DR‾-scheme allowing for an easy connection to high scale tests for, e.g., perturbativity and vacuum stability, and the many observable calculations readily available in MS‾/DR‾ programs. Pure BSM effects are taken into account at the leading order, including all one-loop contributions to loop-induced processes. The program is implemented as an extension to FlexibleSUSY, which determines the mass spectrum for arbitrary BSM models, and does not require any extra configuration from the user. We compare our predictions for Higgs decays in the SM, singlet extended SM, type II THDM, CMSSM and MRSSM, as well as for squark decays in the CMSSM against a selection of publicly available tools. The numerical differences between our and other programs are explained. The release of FlexibleDecay officially deprecates the old effective couplings routines in FlexibleSUSY. Program summaryProgram Title:FlexibleDecayCPC Library link to program files:https://doi.org/10.17632/2c38hcpp5n.1Developer's repository link:https://github.com/FlexibleSUSY/FlexibleSUSYLicensing provisions: GPLv3Programming language: C++, Wolfram Language, Fortran, Bourne shellNature of problem: Calculation of decay widths of scalar bosons in extensions of the Standard Model of particle physics. For the calculation of Higgs boson decay widths known higher-order contributions are taken into account to achieve a high precision.Solution method: The decay widths of the scalar bosons are expressed in terms of Feynman diagrams in a general renormalizable quantum field theory and specialized to the considered model. The resulting expressions are numerically evaluated using special functions and numerical integration.Additional comments including restrictions and unusual features:FlexibleDecay is an addon to FlexibleSUSY [1, 2]. The decay widths can only be calculated in models that can be treated with FlexibleSUSY. Decay widths of fermions or vector bosons are not calculated. For non-Higgs scalar bosons the calculation is restricted to the leading order in the perturbation series.

Models with two Higgs doublets and a light pseudoscalar: A portal to dark matter and the possible (g−2)μ excess

In the context of a two-Higgs doublet model, supplemented by an additional light pseudoscalar Higgs boson and a stable isosinglet fermion, we consider the possibility of addressing simultaneously the discrepancy from the standard expectation of the anomalous magnetic moment of the muon recently measured at Fermilab and the longstanding problem of the dark matter in the universe which can be accounted for by a thermal weakly interacting massive particle. We show that it is indeed possible, for a range of masses and couplings of the new light pseudoscalar and the fermionic states, to explain at the same time the two features while satisfying all other constraints from astroparticle physics and collider searches, including the constraints from flavor physics.

W-mass anomaly in the simplest linear seesaw mechanism

The simplest linear seesaw mechanism can accommodate the new CDF-II W mass measurement. In addition to Standard Model particles, the model includes quasi-Dirac leptons, and a second, leptophilic, scalar doublet seeding small neutrino masses. Our proposal is consistent with electroweak precision tests, neutrino physics, rare decays and collider restrictions, requiring a new charged scalar below a few TeV, split in mass from the new degenerate scalar and pseudoscalar neutral Higgs bosons.

Next-to-soft-virtual resummed prediction for pseudoscalar Higgs boson production at NNLO+NNLL¯

We present first results on the resummation of next-to-soft virtual (NSV) logarithms for the threshold production of pseudoscalar Higgs boson through gluon fusion at the LHC. These results are presented after resumming the NSV logarithms of the kind ${\mathrm{log}}^{i}(1\ensuremath{-}z)$ to $\overline{\mathrm{NNLL}}$ accuracy and matching them systematically to the fixed order NNLO cross sections. These results are obtained using collinear factorization, renormalization group invariance and recent developments in the NSV resummation techniques. The phenomenological implications of these NSV resummed results for 13 TeV LHC are studied and it is observed that these NSV logarithms are quite large. We also evaluate theory uncertainties and find that the renormalization scale uncertainties get reduced further with the inclusion of NSV corrections at various orders in QCD. We further study the impact of QCD corrections on mixed scalar-pseudoscalar states for different values of the mixing angle $\ensuremath{\alpha}$.

Comprehensive study of the light charged Higgs boson in the type-I two-Higgs-doublet model

In the type-I two-Higgs-doublet model, existing theoretical and experimental constraints still permit the light charged Higgs boson with a mass below the top quark mass. We present a complete roadmap for the light charged Higgs boson at the LHC through the comprehensive phenomenology study, focusing on the normal scenario where the lighter \textit{CP}-even Higgs boson is the observed Higgs boson. In type-I, it is challenging to simultaneously accommodate the light mass of the charged Higgs boson and the constraints from theory, electroweak precision data, Higgs data, $b\to s \gamma$, and direct search bounds. Consequently, the parameter space is extremely curtailed, which predicts somewhat definite phenomenological signatures. We find that the mass of the pseudoscalar Higgs boson, $M_A$, is the most crucial factor in the phenomenology of the charged Higgs boson. If $M_A$ is light, the charged Higgs boson decays mainly into $A W^\pm$. When $M_A$ is above the $A W^\pm$ threshold, the dominant decay mode is into $ \tau^\pm \nu$. Over the whole viable parameter space, we study all the possible production and decay modes of charged Higgs bosons at the LHC, and suggest three efficient channels: (i) $pp \to H^+ H^-\to [\tau \nu] [\tau \nu]$; (ii) $pp \to HA/HH/AA \to H^\pm W^\mp H^\pm W^\mp \to [\tau \nu] [\tau \nu] W W$; (iii) $pp \to H^+ H^-\to [b \bar b W ] [b \bar b W ] $. Based on the sophisticated signal-background analyses including detector simulation, we showed that the significance of the first final state is large, that of the second one is marginal around three, but the third one suffers from huge $t\bar t$ related backgrounds.

Search for exotic decays of the Higgs boson into b overline{b} and missing transverse momentum in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

A search for the exotic decay of the Higgs boson (H) into a b overline{b} resonance plus missing transverse momentum is described. The search is performed with the ATLAS detector at the Large Hadron Collider using 139 fb−1 of pp collisions at sqrt{s} = 13 TeV. The search targets events from ZH production in an NMSSM scenario where H → {overset{sim }{chi}}_2^0{overset{sim }{chi}}_1^0 , with {overset{sim }{chi}}_2^0 → a{overset{sim }{chi}}_1^0 , where a is a light pseudoscalar Higgs boson and {overset{sim }{chi}}_{1,2}^0 are the two lightest neutralinos. The decay of the a boson into a pair of b-quarks results in a peak in the dijet invariant mass distribution. The final-state signature consists of two leptons, two or more jets, at least one of which is identified as originating from a b-quark, and missing transverse momentum. Observations are consistent with Standard Model expectations and upper limits are set on the product of cross section times branching ratio for a three-dimensional scan of the masses of the {overset{sim }{chi}}_2^0 , {overset{sim }{chi}}_1^0 and a boson.

Review of a Light NMSSM Pseudoscalar Higgs-State Production at the LHC

In this paper, we briefly review the LHC discovery potential of a light pseudoscalar Higgs boson of the NMSSM, a1, produced in the gluon fusion gg→a1, bottom-quark fusion bb¯→a1 and bottom-gluon fusion bg→ba1. We also review the LHC discovery potential of the next-to-lightest CP-even Higgs boson h2 being the non-SM-like Higgs, decaying either into two light CP-odd Higgs bosons a1 or into a light a1 and the Z gauge boson through the gluon fusion gg→h2 in the 4τ final state. We find that the light a1 can be detected at the LHC in a variety of production processes including the gluon fusion, bottom-quark fusion and bottom-gluon fusion. The latter two processes require high luminosity of the LHC and large values of tanβ. We also find that the LHC has the potential to discover the non-SM-like Higgs state, h2, decaying into a pair of light CP-odd Higgses a1’s, allowing the distinguishing of the NMSSM Higgs sector from the MSSM one as such a light a1, is impossible in the latter scenario.

Detection prospects of a low-mass pseudoscalar Higgs in bottom-quark fusion in the NMSSM at the LHC

The production of a light pseudoscalar Higgs boson in the NMSSM context at the LHC via bottom-quark fusion, bb¯→a1, followed by the a1→τ+τ- decay mode is discussed. We show that there exist some regions of parameter space of the NMSSM in which a low-mass CP-odd Higgs boson can be detected at the high-luminosity LHC via this production mode, provided that tanβ is large enough. Since this production mode has not been studied in the context of the NMSSM so far, we present results for several benchmark points that can be probed by the LHC for extracting the a1 signal. The production of a1 via bottom-quark fusion in the τ+τ- final state can be exploited to measure both the bottom quark and tau lepton Yukawa couplings at the LHC.

Discrimination between the final state of tH and tA using neural network

The Higgs Boson discovered in 2012 at the Large Hadron Collider (LHC) is still assumed to be the Standard Model Higgs Boson -a scalar particle. But there are still possibilities for a pseudo-scalar Higgs Boson. Currently, LHC has not been able to discriminate whether the particle is a scalar, pseudo-scalar, or mixed-scalar-pseudoscalar particle. The focus of this research is in the formulation of the neural network algorithm to discriminate between event signals from a scalar Higgs Boson and pseudo-scalar Higgs Boson in the Higgs production channel of associate production of Higgs Boson with a pair of top-antitop quark in a proton-proton collision pp → tH with center of mass energy with only Higgs decaying to a pair of bottom-antibottom quark had been considered. The set of discriminating variables used is the 3-momentum of all the final state particles. Discriminating efficiency of 0.412 was obtained which showed relatively small discriminating power.

Muon anomalous magnetic moment in two-Higgs-doublet models with vectorlike leptons

We show that inclusion of a single generation of vector-like leptons in the Two-Higgs Doublet Models significantly enlarges the allowed parameter space consistent with the muon anomalous magnetic moment, as well as with other theoretical and experimental constraints. While previously $(g -2)_\mu$ could only be resolved in Type-X scenario by requiring a light pseudoscalar Higgs boson and large $\tan \beta$, contributions of vector-like leptons via two-loop Barr Zee diagrams broaden the allowed parameter space, allowing $\tan \beta$ as low as 10 and pseudoscalar masses as large as $\cal{O}$(1 TeV) while fulfilling the stringent constraints from precision and flavor observable. Similar results are obtained for Type-II scenarios, but there the parameter space is more restricted by flavor observables.

Same-sign charged Higgs boson pair production in bosonic decay channels at the HL-LHC and HE-LHC

Same-sign charged Higgs pair production via vector-boson scattering is a useful probe of the mass spectrum among the heavier scalar, pseudoscalar, and charged Higgs bosons in two-Higgs-doublet models. It has been shown that the production cross section scales as the square of the mass difference $\Delta m = (m_{H^0} - m_{A^0})$ in the alignment limit $(\cos(\beta - \alpha)=0)$. We study the potential measurement of this same-sign charged Higgs pair production at the high-luminosity LHC (HL-LHC) and the proposed 27 TeV $pp$ collider, with emphasis in the decay channel $H^\pm H^\pm \to (W^\pm A^0 ) (W^\pm A^0)$, which is in general the dominant mode when the charged Higgs mass is above the $W^\pm A^0$ threshold. We also examine the current allowed parameter space taking into account the theoretical constraints on the model, the electroweak precision measurements, $B$ decays, and direct searches in the $H^\pm \to \tau^\pm \nu_\tau$ and $H^\pm \to W ^\pm A^0 \to (\ell^\pm\nu_{\ell} ) (\mu \mu)$.

Search for a light pseudoscalar Higgs boson in the boosted \u03bc\u03bc\u03c4\u03c4 final state in proton-proton collisions at sqrt{s} = 13 TeV

A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at sqrt{s} = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ, and considers pseudoscalar masses in the range 3.6 < ma< 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of ma, on the branching fraction (ℬ) for H → aa → μμττ, down to 1.5 (2.0) × 10−4 for mH = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV.

Polarized mathrm{q}overline{mathrm{q}} \u2192 Z+Higgs amplitudes at two loops in QCD: the interplay between vector and axial vector form factors and a pitfall in applying a non-anticommuting \u03b35

We consider QCD corrections to two loops for the polarized amplitudes of qoverline{q} → Z + Higgs boson. First we show how the polarized amplitudes of boverline{b} → Zh associated with a non-vanishing b-quark Yukawa coupling and a scalar or pseudoscalar Higgs boson h can be built up solely from vector form factors (FF) of properly grouped classes of diagrams, bypassing completely the need of explicitly manipulating γ5 in dimensional regularization (up to a few “anomalous”, i.e., triangle diagrams). We determine the contributions of the triangle diagrams in the heavy top limit. We present the analytic results of the vector FF and the triangle-diagram contributions to the axial vector FF, which are sufficient for deriving the two-loop QCD amplitudes for boverline{b} → Zh with a CP-even and CP-odd Higgs boson h. We derive the respective Ward identity for these amplitudes, which are subsequently verified to two-loop order in QCD using these FF. In addition, the FF of a class of corrections to qoverline{q} → ZH proportional to the top-Yukawa coupling are obtained analytically to two-loop order in QCD in the heavy-top limit using the Higgs-gluon effective Lagrangian where the top quark is integrated out. We address a pitfall that occurs when applying the non-anticommutating γ5 prescription to this class of contributions that has been overlooked so far in the literature. We attribute this issue to the fact that the absence of certain heavy-mass expanded diagrams in the infinite-mass limit of a scattering amplitude with an axial vector current depends on the particular γ5 prescription in use.

Search for a light pseudoscalar Higgs boson in the boosted $\mu\mu\tau\tau$ final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV

Search for a light pseudoscalar Higgs boson in the boosted $\mu\mu\tau\tau$ final state in proton-proton collisions at $\sqrt{s}=$ 13 TeV