Higgs Boson Mass Research Articles

The heavy gluino in natural no-scale [formula omitted]-SU(5)

In light of recent 80–137 fb−1 results at the LHC Run 2 establishing a lower gluino mass limit of 2.25 TeV, we revisit the supersymmetric GUT model Flipped SU(5) with extra vector-like particles, known as F-SU(5), with vanishing No-Scale Supergravity boundary conditions at the string scale of about 2×1017 GeV, including the supersymmetry breaking Bμ parameter which is strictly enforced as Bμ=0. Given the proportional dependence of all model scales on a single parameter M1/2, No-Scale F-SU(5) was shown to possess no electroweak fine-tuning and thus persists as a natural one-parameter model. In this fresh analysis here, we demand consistency with the measured 125 GeV light Higgs boson mass, though we forgo an upper limit on the lightest neutralino relic density. The resulting phenomenology delivers a gluino mass of M(g˜)≲7.5 TeV and a lightest supersymmetric particle (LSP) of M(χ˜10)≲1.6 TeV. In order to dilute the relic density down to the WMAP and Planck measurements, we rely upon a single cosmological master coupling λ6.

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Foreword

Search for dark photons in decays of Higgs bosons produced in association with Z bosons in proton-proton collisions at sqrt{s} = 13 TeV

A search is presented for a Higgs boson that is produced in association with a Z boson and that decays to an undetected particle together with an isolated photon. The search is performed by the CMS Collaboration at the Large Hadron Collider using a data set corresponding to an integrated luminosity of 137 fb−1 recorded at a center-of-mass energy of 13 TeV. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for associated Higgs and Z boson production and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a mass of 125 GeV, assuming the standard model production cross section, this corresponds to an observed (expected) upper limit on this branching fraction of 4.6 (3.6)% at 95% confidence level. These are the first limits on Higgs boson decays to final states that include an undetected massless dark photon.

Mass Reconstruction of MSSM Higgs Boson

The problems of the Standard Model, as well as questions related to Higgs boson properties led to the need to model the ttH associated production and the Higgs boson decay to a top quark pair within the MSSM model. With the help of computer programs MadGraph, Pythia, and Delphes and using the latest kinematic cuts taken from experimental data obtained at the LHC, we have predicted the masses of MSSM Higgs bosons, A and H.

The Electroweak Phase Transition in a Spontaneously Magnetized Plasma

We investigate the electroweak phase transition (EWPT) in the Minimal (One Higgs doublet) Standard Model (SM) with account for the spontaneous generation of magnetic and chromo-magnetic fields. As it is known, in the SM for the mass of a Higgs boson greater than 75 GeV, this phase transition is of the second order. But, according to Sakharov’s conditions for the formation of the baryon asymmetry in the early Universe, it has to be strongly of the first order. In the Two Higgs doublets SM, there is a parametric space, where the first-order phase transition is realized for the realistic Higgs boson mass mH = 125 GeV. On the other hand, in the hot Universe, the spontaneous magnetization of a plasma had happened. The spontaneously generated (chromo) magnetic fields are temperature-dependent. They influence the EWРT. The color chromomagnetic fields B3 and B8 are created spontaneously in the gluon sector of QCD at a temperature T > Td higher the deconfinement temperature Td. The usual magnetic field H has also to be spontaneously generated. For T close to the TEWPT , these magnetic fields could change the kind of the phase transition.

Charged Higgs bosons in the NMSSM under current LHC constraints

Charged Higgs boson is a crucial prediction of new physics beyond the SM. In this work, we perform a comprehensive scan over the parameter space of NMSSM considering various experimental constraints including the direct search limits from the 13 TeV LHC, and consider the scenario that the next-to-lightest CP-even Higgs boson is SM-like. We find that the masses of charged Higgs bosons can be as light as 350 GeV, the lightest CP-even Higgs boson [Formula: see text] is predominantly singlet and can be as light as 48 GeV, and the lightest CP-odd Higgs boson [Formula: see text] is also singlet-dominated and can be as light as 82 GeV. The charged Higgs bosons mainly decay to [Formula: see text] or [Formula: see text], but the branching ratio of the exotic decays [Formula: see text] and [Formula: see text] can maximally reach 20% and 11%, respectively, which can be used to distinguish the NMSSM from MSSM. Such a heavy charged Higgs boson is inaccessible at the 13 TeV LHC with a luminosity of 36.1 fb[Formula: see text] and its detection needs higher energy and/or higher luminosity.

Effective scanning method of the NMSSM parameter space

The next-to-minimal supersymmetric standard model (NMSSM) naturally provides a 125 GeV Higgs boson without the need for large loop corrections from multi-TeV stop quarks. Furthermore, the NMSSM provides an electroweak scale dark matter candidate consistent with all experimental data, like relic density and non-observation of direct dark matter signals with the present experimental sensitivity. However, more free parameters are introduced in the NMSSM, which are strongly correlated. A simple parameter scan without knowing the correlation matrix is not efficient and can miss significant regions of the parameter space. We introduce a new technique to sample the NMSSM parameter space, which takes into account the correlations. For this we project the 7D NMSSM parameter space onto the 3D Higgs boson mass parameter space. The reduced dimensionality allows for a non-random sampling and therefore a complete coverage of the allowed NMSSM parameters. In addition, the parameter correlations and possible deviations of the signal strengths of the observed 125 Higgs boson from the SM values are easily predicted.

Model-independent search strategy for the lepton-flavor-violating heavy Higgs boson decay to {tau mu } at the LHC

In this work we present a model-independent search strategy at the LHC for heavy Higgs bosons decaying into a tau and a muon, H/A rightarrow tau mu , showing a plausible tendency to improve the sensitivity obtained by the present experimental limits. This search strategy is performed for the Higgs boson mass range 1–5 TeV and uses as the most relevant kinematical variables, in order to discriminate signal against background, the transverse momenta of the muon and the tau together with the missing transverse energy. We estimate the exclusion limits at 95% CL and the significances for evidence and discovery at sqrt{s} = 14 TeV with mathcal {L} = 300 fb^{-1}, observing a growth in the sensitivities for high Higgs boson masses. Moreover, since the Higgs boson decay into a tau-lepton pair may mimic our LFV signal, we also study the impact of the ditau channel on the exclusion limits and the significances for evidence and discovery. In particular, the impact on the exclusion limits of LFV heavy Higgs boson decays is significant when the ditau rate begins to compete with the corresponding to the H/A rightarrow tau mu decay.

Catalysis of the 〈b̄b〉 Condensate in the Composite Higgs Model

The problem of appearance of quark masses through the mechanism of dynamical breaking of the SU(2)L × U(1)R symmetry of electroweak interactions has been studied within a model with local four-quark interactions, which result in the formation of a 〈tt〉 condensate and composite Higgs bosons. We show that this process catalyzes bb condensation in the presence of an arbitrarily weak’ t Hooft interaction. The spectrum of composite scalar excitations has been calculated. An expression obtained for the mass of a standard Higgs boson significantly improves the agreement of the top-condensation model with the experiment. It has been shown that the standard Higgs boson under the Nambu sum rules should have three partners with the same mass of about 245 GeV and different electric charges. The possibility of a transition of the system to a chiral symmetric phase, which is accompanied by the corresponding change in the spectrum of elementary excitations, is discussed.

Almost inert Higgs bosons at the LHC

Non-minimal Higgs sectors are strongly constrained by the agreement of the measured couplings of the 125 GeV Higgs with Standard Model predictions. This agreement can be explained by an approximate ℤ2 symmetry under which the additional Higgs bosons are odd. This allows the additional Higgs bosons to be approximately inert, meaning that they have suppressed VEVs and suppressed mixing with the Standard Model Higgs. In this case, single production of the new Higgs bosons is suppressed, but electroweak pair production is unsuppressed. We study the phenomenology of a minimal 2 Higgs doublet model that realizes this scenario. In a wide range of parameters, the phenomenology of the model is essentially fixed by the masses of the exotic Higgs bosons, and can therefore be explored systematically. We study a number of different plausible signals in this model, and show that several LHC searches can constrain or discover additional Higgs bosons in this parameter space. We find that the reach is significantly extended at the high luminosity LHC.

Ultraviolet complete quantum field theory and particle model

An ultraviolet complete particle model is constructed for the observed particles of the standard model. The quantum field theory associates infinite derivative entire functions with propagators and vertices, which make quantum loops finite and maintain Poincar\'e invariance and unitarity of the model. The electroweak model $SU(2)\times U(1)$ group is treated as a broken symmetry group with non-vanishing experimentally determined boson and fermion masses. A spontaneous symmetry breaking of the vacuum by a scalar Higgs field is not invoked to restore boson and fermion masses to the initially massless $SU(2)\times U(1)$ Lagrangian of the standard model. The hierarchy naturalness problem of the Higgs boson mass is resolved and the model contains only experimentally observed masses and coupling constants. The model can predict a stable vacuum evolution. Experimental tests to distinguish the standard model from the alternative model are proposed. The finite quantum field theory can be extended to quantum gravity.

Dynamical symmetry breaking and negative cosmological constant

In the context of Clifford functional integral formalism, we revisit the Nambu–Jona-Lasinio-type dynamical symmetry breaking model and examine the properties of the dynamically generated composite bosons. Given that the model with 4-fermion interactions is nonrenormalizable in the traditional sense, the aim is to gain insight into the divergent integrals without resorting to explicit regularization. We impose a restriction on the linearly divergent primitive integrals, thus resolving the long-standing issue of momentum routing ambiguity associated with fermion–antifermion condensations. The removal of the ambiguity paves the way for the possible calculation of the true ratio of Higgs boson mass to top quark mass in the top condensation model. In this paper, we also investigate the negative vacuum energy resulted from dynamical symmetry breaking and its cosmological implications. In the framework of modified Einstein–Cartan gravity, it is demonstrated that the late-time acceleration is driven by a novel way of embedding the Hubble parameter into the Friedmann equation via an interpolation function, whereas the dynamically generated negative cosmological constant only plays a minor role for the current epoch. Two cosmic scenarios are proposed, with one of which suggesting that the universe may have been evolving from an everlasting coasting state towards the accelerating era characterized by the deceleration parameter approaching −0.5 at low redshift. One inevitable outcome of the modified Friedmannian cosmology is that the directly measured local Hubble parameter should in general be larger than the Hubble parameter calibrated from the conventional Friedmann equation. This Hubble tension becomes more pronounced when the Hubble parameter is comparable or less than a characteristic Hubble scale.

Fermion mass hierarchy in grand gauge-Higgs unification

Abstract Grand gauge-Higgs unification of 5D $SU(6)$ gauge theory on an orbifold $S^1/Z_2$ is discussed. The Standard Model (SM) fermions are introduced on one of the boundaries and some massive bulk fields are also introduced so that they couple to the SM fermions through the mass terms on the boundary. Integrating out the bulk fields generates SM fermion masses with exponentially small bulk mass dependences. The SM fermion masses except for the top quark are shown to be reproduced by mild tuning of the bulk masses. The one-loop Higgs potential is calculated and it is shown that electroweak symmetry breaking occurs by introducing additional bulk fields. The Higgs boson mass is also computed.

Precise prediction for the Higgs-Boson masses in the {varvec{mu }}{varvec{nu }}SSM with three right-handed neutrino superfields

The mu nu mathrm {SSM} is a simple supersymmetric extension of the Standard Model (SM) capable of describing neutrino physics in agreement with experiments. We perform the complete one-loop renormalization of the neutral scalar sector of the mu nu mathrm {SSM} with three generation of right-handed neutrinos in a mixed on-shell/smash {overline{mathrm {DR}}} scheme. We calculate the full one-loop corrections to the neutral scalar masses of the mu nu mathrm {SSM}. The one-loop contributions are supplemented by available MSSM higher-order corrections. We obtain numerical results for a SM-like Higgs-boson mass consistent with experimental bounds, while simultaneously agreeing with neutrino oscillation data. We illustrate the distinct phenomenology of the mu nu mathrm {SSM} in scenarios in which one or more right-handed sneutrinos are lighter than the SM-like Higgs boson, which might be substantially mixed with them. These scenarios are experimentally accessible, on the one hand, through direct searches of the right-handed sneutrinos decaying into SM particles, and on the other hand, via the measurements of the SM-like Higgs-boson mass and its couplings. In this way the parameter space of the mu nu mathrm {SSM} can be probed without the need to propose model dependent searches at colliders. Finally, we demonstrate how the mu nu mathrm {SSM} can simultaneously accommodate two excesses measured at LEP and LHC at sim 96,, mathrm {GeV} at the 1sigma level, while at the same time reproducing neutrino masses and mixings in agreement with neutrino oscillation measurements.

Two-loop mathcal{O} ( {alpha}_t^2 ) corrections to the neutral Higgs boson masses in the CP-violating NMSSM

We present our calculation of the two-loop corrections of mathcal{O} ( {alpha}_t^2 ) to the neutral Higgs boson masses of the CP-violating Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM). The calculation is performed in the Feynman diagrammatic approach in the gaugeless limit at vanishing external momentum. We apply a mixed overline{mathrm{DR}} -on-shell (OS) renormalization scheme for the NMSSM input parameters. Furthermore, we exploit a overline{mathrm{DR}} as well as an OS renormalization in the top/stop sector. The corrections are implemented in the Fortran code NMSSMCALC for the calculation of the Higgs spectrum both in the CP-conserving and CP-violating NMSSM. The code also provides the Higgs boson decays including the state-of-the-art higher-order corrections. The corrections computed in this work improve the already available corrections in NMSSMCALC which are the full one-loop corrections without any approximation and the two-loop mathcal{O} (αtαs) corrections in the gaugeless limit and at vanishing external momentum. Depending on the chosen parameter point, we find that the O(αtαs + {alpha}_t^2 ) corrections add about 4-7% to the one-loop mass of the SM-like Higgs boson for overline{mathrm{DR}} renormalization in the top/stop sector and they reduce the mass by about 6-9% if OS renormalization is applied. For an estimate of the theoretical uncertainty we vary the renormalization scale and change the renormalization scheme and show that care has to be taken in the corresponding interpretation.

Phenomenology of Higgs bosons in inverse seesaw model with Type-X two Higgs doublet at the LHC

Type-X two Higgs doublet model is known to explain the muon g − 2 anomaly with a relatively light charged Higgs boson at large tan β. The light charged Higgs boson has been searched in the main τ ν mode at the colliders. Invoking a scenario of inverse seesaw as the origin of neutrino masses and mixing, the charged Higgs boson can decay additionally to right-handed neutrinos which leads to interesting phenomenology. Considering generic lepton flavour violating signatures at the final states, a 5σ discovery can be achieved with the early data of LHC, at 14 TeV, for relatively large inverse seesaw Yukawa coupling YN. The very light pseudoscalar and charged Higgs boson mass reconstruction are performed using the new modes and the results look promising. The inverse seesaw Yukawa coupling is shown to be probed down to YN ∼ 0.2 at HL LHC with 3000 fb−1.

Muon g-2 in Split-Family SUSY in light of LHC run II

The Split-Family supersymmetry is a model in which the sfermion masses of the first two generations are in {mathcal {O}}(100{-}{1000}),hbox {GeV} while that of the third one is in {mathcal {O}}(10) TeV. With such a hierarchical spectrum, the deviation of the muon g-2 and the observed Higgs boson mass are explained simultaneously. In this paper, we revisit the Split-Family SUSY model in light of the updated LHC constraints. We also study the flavor changing neutral current problems in the model. As we will show, the problems do not lead to stringent constraints when the Cabibbo-Kobayashi-Maskawa matrix is the only source of the flavor mixing. We also study how large flavor mixing in the supersymmetry breaking parameters is allowed.

Where are the next Higgs bosons?

Simple symmetry arguments applied to the third generation lead to a prediction: there exist new sequential Higgs doublets with masses of order $\lesssim 5 $ TeV, with approximately universal Higgs-Yukawa coupling constants, $g\sim 1$. This is calibrated by the known Higgs boson mass, the top quark Higgs-Yukawa coupling, and the $b$-quark mass. A new massive weak-isodoublet, $H_b$, coupled to the $b$-quark with $g\sim 1$ is predicted, and may be accessible to the LHC at $13$ TeV, and definitively at the energy upgraded LHC of $26$ TeV. The extension to leptons generates a new $H_\tau$ and a possible $H_{\nu_\tau}$ doublet. The accessibility of the latter depends upon whether the mass of the $\tau$-neutrino is Dirac or Majorana.

Naturalness in D-brane inspired models

We examine the naturalness of the D-brane inspired model constructed in flipped SU(5) supplemented with vector-like particles at the TeV scale, dubbed flippons. We find the model can produce a mainly Higgsino-like lightest supersymmetric particle (LSP) and small light stops, as favored by naturalness. In fact, a large trilinear scalar At term at the electroweak (EW) scale creates a large mass splitting between the top squarks, driving the light stop to near degeneracy with an LSP that is almost all Higgsino, with Delta Mleft({tilde{t}}_1,{tilde{chi}}_1^0right) < 5GeV, evading the LHC constraint on {tilde{t}}_1to c{tilde{chi}}_1^0 thus far. Given the smallness of the light stop, generating a 125 GeV light Higgs boson mass is aided by one-loop contributions from the Yukawa couplings between the flippons and Higgs fields. The resulting parameter space satisfying naturalness is rather constrained, thus we assess its viability by means of comparison to the LHC constraint on soft charm jets and direction detection limits on spin-independent cross-sections. Finally, we compute the level of electroweak fine-tuning and uncover a region with ΔEW< 30, i.e., fine-tuning better than 3%, regarded as low electroweak fine-tuning. Given the small light stop, the electroweak fine-tuning from only the top squarks is of mathcal{O} (1), indicating no fine-tuning from neither the light stop {tilde{t}}_1 nor the heavy stop {tilde{t}}_2 .

MSSM Higgs boson searches at the LHC: benchmark scenarios for Run 2 and beyond

We propose six new benchmark scenarios for Higgs boson searches in the Minimal Supersymmetric Standard Model. Our calculations follow the recommendations of the LHC Higgs Cross Section Working Group, and benefit from recent developments in the predictions for the Higgs-boson masses and mixing. All of the proposed scenarios are compatible with the most recent results from Run 2 of the LHC. In particular, they feature a scalar with mass and couplings compatible with those of the observed Higgs boson, and a significant portion of their parameter space is allowed by the limits from the searches for SUSY particles and additional Higgs bosons. We define a scenario where all SUSY particles are relatively heavy, and two scenarios with light colorless SUSY particles (charginos, neutralinos and, in one case, staus). In addition, we present two scenarios featuring alignment without decoupling, realized with either the lighter or the heavier scalar being SM-like, and a scenario with mathcal {CP} violation.