Higgs Mass Research Articles

Towards a Higgs mass determination in asymptotically safe gravity with a dark portal

There are indications that an asymptotically safe UV completion of the Standard Model with gravity could constrain the Higgs self-coupling, resulting in a prediction of the Higgs mass close to the vacuum stability bound in the Standard Model. The predicted value depends on the top quark mass and comes out somewhat higher than the experimental value if the current central value for the top quark mass is assumed. Beyond the Standard Model, the predicted value also depends on dark fields coupled through a Higgs portal. Here we study the Higgs self-coupling in a toy model of the Standard Model with quantum gravity that we extend by a dark scalar and fermion. Within the approximations used in [1], there is a single free parameter in the asymptotically safe dark sector, as a function of which the predicted (toy model) Higgs mass can be lowered due to mixing effects if the dark sector undergoes spontaneous symmetry breaking.

Self-organised localisation

We describe a new phenomenon in quantum cosmology: self-organised localisation. When the fundamental parameters of a theory are functions of a scalar field subject to large fluctuations during inflation, quantum phase transitions can act as dynamical attractors. As a result, the theory parameters are probabilistically localised around the critical value and the Universe finds itself at the edge of a phase transition. We illustrate how self-organised localisation could account for the observed near-criticality of the Higgs self-coupling, the naturalness of the Higgs mass, or the smallness of the cosmological constant.

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 $\mathrm{tan}\ensuremath{\beta}$.

Fermions, Gauge Bosons and Higgs Masses in the 3-3-1-1 Model with Charged Lepton

A new version of 3-3-1-1 model proposed can solve the Landau pole problem of the previous versions. The masses of fermions are calculated in detail where the masses of active neutrinos are generated through the seesaw mechanism. All the Higgs bosons and gauge bosons as well as their masses are identified and calculated.

Challenges for inflaton dark matter

We examine an intriguing possibility that a single field is responsible for both inflation and dark matter, focusing on the minimal set–up where inflation is driven by a scalar coupling to curvature. We study in detail the reheating process in this framework, which amounts mainly to particle production in a quartic potential, and distinguish thermal and non–thermal dark matter options. In the non–thermal case, the reheating is impeded by backreaction and rescattering, making this possibility unrealistic. On the other hand, thermalized dark matter is viable, yet the unitarity bound forces the inflaton mass into a narrow window close to half the Higgs mass.

Two-loop mathcal{O} ((\u03b1t + \u03b1\u03bb + \u03b1\u03ba)2) corrections to the Higgs boson masses in the CP-violating NMSSM

We present our computation of the mathcal{O} ((αt + αλ + ακ)2) two-loop corrections to the Higgs boson masses of the CP-violating Next-to-Minimal Supersymmetric Standard Model (NMSSM) using the Feynman-diagrammatic approach in the gaugeless limit at vanishing external momentum. We choose a mixed overline{mathrm{DR}} -on-shell (OS) renormalisation scheme for the Higgs sector and apply both overline{mathrm{DR}} and OS renormalisation in the top/stop sector. For the treatment of the infrared divergences we apply and compare three different regularisation methods: the introduction of a regulator mass, the application of a small momentum expansion, and the inclusion of the full momentum dependence. Our new corrections have been implemented in the Fortran code NMSSMCALC that computes the Higgs mass spectrum of the CP-conserving and CP-violating NMSSM as well as the Higgs boson decays including the state-of-the-art higher-order corrections. Our numerical analysis shows that the newly computed corrections increase with rising λ and κ, remaining overall below about 3% compared to our previously computed mathcal{O} (αt(αt + αs)) corrections, in the region compatible with perturbativity below the GUT scale. The renormalisation scheme and scale dependence is of typical two-loop order. The impact of the CP-violating phases in the new corrections is small. We furthermore show that the Goldstone Boson Catastrophe due to the infrared divergences can be treated in a numerically efficient way by introducing a regulator mass that approximates the momentum-dependent results best for squared mass values in the permille range of the squared renormalisation scale. Our results mark another step forward in the program of increasing the precision in the NMSSM Higgs boson observables.

High P_T Higgs excess as a signal of non-local QFT at the LHC

Non-local extensions of the Standard Model with a non-locality scale varLambda _{NL} have the effect of smearing the pointlike vertices of the Standard Model. At energies significantly lower than varLambda _{NL} vertices appear pointlike, while beyond this scale all beta functions vanish and all couplings approach a fixed point leading to scale invariance. Non-local SM extensions are ghost free, with the non-locality scale serving as an effective cutoff to radiative corrections of the Higgs mass. We argue that the data expected to be collected at the LHC phase 2 will have a sensitivity to non-local effects originating from a non-locality scale of a few TeV. Using an infinite derivative prescription, we study modifications to heavy vector-boson cross sections that can lead to an enhanced production of boosted Higgs bosons in a region of the kinematic phase space where the SM background is very small.

Exploring the low tan beta region of two Higgs doublet models at the LHC

Current interpretations of the LHC results on two Higgs doublet models (2HDM) underestimate the sensitivity due to neglecting higher order effects. In this work, we revisit the impact of these effects using the current cross-section times branching ratio limits of the Arightarrow hZ, H rightarrow VV and Hrightarrow hh channels. With a degenerate heavy Higgs mass m_varPhi , we find that the LHC searches gain sensitivity to the small tan beta region after including loop corrections, even close to cos (beta -alpha )=0 which is not reachable at tree level for all types of 2HDM. For a benchmark point with m_varPhi =300 GeV, tan beta <1.8(1.2) can be probed for the Type-I(II) 2HDM model for cos (beta -alpha )=0. When the deviation from cos (beta -alpha )=0 is larger, the region for which current searches have exclusion potential becomes larger.

Measurements of Higgs properties from CMS

<p indent=0mm>The Large Hadron Collider (LHC) exhibits the highest colliding energy in the world. The compact muon solenoid (CMS) is one of the main experiments conducted on the LHC, and its objective is to discover the Higgs boson and new particles. In this report, the discovery of the Higgs Boson and the measurements of Higgs properties using CMS RUN2 data were briefly presented. Higgs production modes—ggH, VBF, VH, and ttH—were observed using the CMS, and decay modes— ZZ to four leptons, diphotons, WW, ττ, and bb—were discovered using the CMS. Higgs coupling with vector bosons and third-generation fermions t, b, and τ were measured. Moreover, the Higgs mass, width, decay branching ratio, spin and parity, cross-section, and differential cross-section were studied. The results are consistent with those obtained using the standard model within an error range. The results are mainly obtained using 2016 data, and the errors are large. Nevertheless, the results will be improved when all RUN2 data analyses are published.

Mass gap in strongly coupled infinite derivative non-local Higgs: Dyson–Schwinger approach

We investigate the non-perturbative degrees of freedom (d.o.f.) in the class of non-local Higgs theories that have been proposed as an ultraviolet completion 4D quantum field theory generalizing the kinetic energy operators to an infinite series of higher derivatives inspired by string field theory and ghost-free non-local approaches to quantum gravity. At the perturbative level, the d.o.f. of non-local Higgs are the same of the local theory. We prove that, at the non-perturbative level, the physical spectrum of the strongly-coupled Higgs mass is actually corrected from the ‘infinite number of derivatives’ present in the action. The technique we use permits to derive the set of Dyson–Schwinger equations in differential form. This proves essentially useful when exact solutions to the local equations are known. We show that all the formalism of the local theory involving the Dyson–Schwinger approach extends quite naturally to the non-local case. Using these methods, the spectrum of the strongly-coupled non-local theories become accessible in the non-perturbative regimes. We calculate the N-point correlation functions and predict the mass-gap in the spectrum arising purely from the self-interaction and the non-local scale M. The proper weak perturbation limit is correctly recovered from the strong coupling regime in the limit of the coupling of the theory goes to zero. Our results show the mass gap generated in the non-local theories gets damped in the UV and it reaches conformal limit. We discuss the implications of our result in particle physics and cosmology.

A model of muon anomalies

The Standard Model (SM) is augmented with a U(1)B−3Lμ gauge symmetry spontaneously broken above the TeV scale when an SM-singlet scalar condenses. Scalar leptoquarks S1(3)=(3‾,1(3),13) charged under U(1)B−3Lμ mediate the intriguing effects observed in muon (g−2), RK(⁎), and b→sμ+μ− angular distributions, while generically evading all other phenomenological constraints. The fermionic sector is minimally extended with three right-handed neutrinos, and a successful type-I seesaw mechanism is realized. Charged lepton flavor violation is effectively suppressed, and proton decay—a common prediction of leptoquarks—is postponed to the dimension-6 effective Lagrangian. Unavoidable radiative corrections in the Higgs mass and muon Yukawa favor leptoquark masses interesting for collider searches. The parameters of the model are radiatively stable and can be evolved by the renormalization group to the Planck scale without inconsistencies. Alternative lepton-flavored gauge extensions of the SM, under which leptoquarks become muoquarks, are proposed for comparison.

A common origin of muon g-2 anomaly, Galaxy Center GeV excess and AMS-02 anti-proton excess in the NMSSM

The supersymmetric model is one of the most attractive extensions of the Standard Model of particle physics. In light of the most recently reported anomaly of the muon g-2 measurement by the FermiLab E989 experiment, and the excesses of gamma rays at the Galactic center observed by Fermi-LAT space telescope, as well as the antiproton excess observed by the Alpha Magnetic Spectrometer, we propose to account for all these anomalies or excesses in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Considering various experimental constraints including the Higgs mass, B-physics, collider data, dark matter relic density and direct detections, we find that a ~60 GeV bino-like neutralino is able to successfully explain all these observations. Our scenario can be sensitively probed by future direct detection experiments.

Minimal twist for the Standard Model in noncommutative geometry: The field content

Noncommutative geometry provides both a unified description of the Standard Model of particle physics together with Einstein-Hilbert action (in euclidean signature) and some tools to go beyond the Standard Model. In this paper, we extend to the full noncommutative geometry of the Standard Model the twist (in the sense of Connes-Moscovici) initially worked out for the electroweak sector and the free Dirac operator only. Namely, we apply the twist also to the strong interaction sector and the finite part of the Dirac operator. To do so, we are forced to take into account a violation of the twisted first-order condition. As a result, we still obtain the extra scalar field required to stabilise the electroweak vacuum and fit the Higgs mass, but it now has two chiral components. We also get the additive field of 1-forms already pointed out in the electroweak model, but with a richer structure. Finally, we obtain a pair of Higgs doublets, which are expected to combine into a single Higgs doublet in the action formula, as will be investigated in the second part of this work.

The Higgs potential in 2HDM extended with a real triplet scalar: A roadmap

We perform a comprehensive study of the Higgs potential of the two Higgs doublet model extended by a real triplet scalar field [Formula: see text]. This model, dubbed [Formula: see text], has a rich Higgs spectrum consisting of three CP-even Higgs [Formula: see text], one CP-odd [Formula: see text] and two pairs of charged Higgs [Formula: see text]. First, we determine the perturbative unitarity constraints and a set of nontrivial conditions for the boundedness from below (BFB). Then we derive the Veltman conditions by considering the quadratic divergencies of Higgs boson self-energies in [Formula: see text]. We find that the parameter space is severely delimited by these theoretical constraints, as well as experimental exclusion limits and Higgs signal rate measurements at LEP and LHC. Using HiggsBounds-5.3.2beta and HiggSignals-2.2.3beta public codes, an exclusion test at [Formula: see text] is then performed on the physical scalars of [Formula: see text]. Our analysis provides a clear insight on the nonstandard scalar masses, showing that the allowed ranges are strongly sensitive to the sign of mixing angle [Formula: see text], essentially when naturalness is involved. For [Formula: see text] scenario, our results place higher limits on the bounds of all scalar masses, and show that the pairs [Formula: see text] and [Formula: see text] are nearly mass degenerate varying within the intervals [Formula: see text] GeV and [Formula: see text] GeV, respectively. When [Formula: see text] turns positive, we show that consistency with theoretical constraints and current LHC data, essentially on the diphoton decay channel, favors Higgs masses varying within wide allowed ranges: [Formula: see text] GeV for [Formula: see text]; [Formula: see text] GeV for ([Formula: see text], [Formula: see text]) and [Formula: see text] GeV for ([Formula: see text], [Formula: see text]). Finally, we find that the [Formula: see text] and [Formula: see text] Higgs decay modes are generally correlated if [Formula: see text] lies within the reduced intervals [Formula: see text] and [Formula: see text] parameter is frozen around [Formula: see text] ([Formula: see text]) for [Formula: see text] ([Formula: see text]).

Dynamical inverse seesaw mechanism as a simple benchmark for electroweak breaking and Higgs boson studies

The Standard Model (SM) vacuum is unstable for the measured values of the top Yukawa coupling and Higgs mass. Here we study the issue of vacuum stability when neutrino masses are generated through spontaneous low-scale lepton number violation. In the simplest dynamical inverse seesaw, the SM Higgs has two siblings: a massive CP-even scalar plus a massless Nambu-Goldstone boson, called majoron. For TeV scale breaking of lepton number, Higgs bosons can have a sizeable decay into the invisible majorons. We examine the interplay and complementarity of vacuum stability and perturbativity restrictions, with collider constraints on visible and invisible Higgs boson decay channels. This simple framework may help guiding further studies, for example, at the proposed FCC facility.

Fighting off field dependence in MSSM Higgs-mass corrections of order alpha _t,alpha _s and alpha _t^2

The connection between gauge and Higgs sectors makes supersymmetric extensions of the Standard Model predictive frameworks for the derivation of Higgs masses. In this paper, we study the contamination of such predictions by field-renormalization constants, in the MSSM with two-loop gaugeless corrections of mathcal {O}big (alpha _{t,b},alpha _s,,alpha _{t,b}^2big ) and full momentum dependence, and demonstrate how strict perturbative expansions allow to systematically neutralize the dependence on such unphysical objects. On the other hand, the popular procedure consisting in an iterative pole search remains explicitly dependent on field counterterms. We then analyze the magnitude of the intrinsic uncertainty that this feature implies for the iterative method, both in non-degenerate and near-degenerate regimes, and conclude that this strategy does not improve on the predictions of the more straightforward expansion. We also discuss several features related to the inclusion of the orders alpha _{t,b},alpha _s and alpha _{t,b}^2 in the so-called ‘fixed-order’ approach, such as the resummation of UV-logarithms for heavy supersymmetric spectra.

Anomalous muon magnetic moment, supersymmetry, naturalness, LHC search limits and the landscape

The recent measurement of the muon anomalous magnetic moment aμ≡(g−2)μ/2 by the Fermilab Muon g−2 experiment sharpens an earlier discrepancy between theory and the BNL E821 experiment. We examine the predicted Δaμ≡aμ(exp)−aμ(th) in the context of supersymmetry with low electroweak naturalness (restricting to models which give a plausible explanation for the magnitude of the weak scale). A global analysis including LHC Higgs mass and sparticle search limits points to interpretation within the normal scalar mass hierarchy (NSMH) SUSY model wherein first/second generation matter scalars are much lighter than third generation scalars. We present a benchmark model for a viable NSMH point which is natural, obeys LHC Higgs and sparticle mass constraints and explains the muon magnetic anomaly. Aside from NSMH models, then we find the (g−2)μ anomaly cannot be explained within the context of natural SUSY, where a variety of data point to decoupled first/second generation scalars. The situation is worse within the string landscape where first/second generation matter scalars are pulled to values in the 10−50 TeV range. An alternative interpretation for SUSY models with decoupled scalar masses is that perhaps the recent lattice evaluation of the hadronic vacuum polarization could be confirmed which leads to a Standard Model theory-experiment agreement in which case there is no anomaly.

Top–Bottom Condensation Model: Symmetries and Spectrum of the Induced 2HDM

Here, we use the Schwinger–DeWitt approach to address the four-fermion composite Higgs effective model proposed by Miransky, Tanabashi and Yamawaki (MTY). The surprising benefit of such an approach is that it is possible to ascribe to a SM-type Higgs a quark–antiquark structure of predominantly a b¯b nature with a small t¯t admixture, which in turn yields a Higgs mass compatible with the observed value of 125 GeV. We discuss this result in a detailed and pedagogical way, as it goes against the common belief that this model and akin composite descriptions should predict a Higgs mass-of-order of twice the top quark mass, contrary to empirical evidence. A further aspect of this approach is that it highlights the link of the SU(2)L×U(1)R symmetric four-fermion MTY model interactions of the heavy quark family to a specific two-Higgs-doublet model (2HDM), and the necessity to go beyond the one Higgs doublet to obtain the empirical Higgs mass within composite models. By appropriately fixing the symmetry-defining interaction parameters, we show that the resulting CP-preserving spectrum harbors the following collective states at the electroweak scale ΛEW=246 GeV: a light scalar to which the standard Higgs is associated; a heavier neutral state preconized as the Nambu partner of the standard Higgs within the Nambu sum rule; the expected triplet of Goldstone bosons associated with the longitudinal polarizations of the electroweak massive bosons; and a neutral pseudoscalar state that in the limit of a global U(1)A symmetry would be a Goldstone mode. The anomalous breaking of this axial symmetry is a subleading effect in a large Nc counting scheme, and we discuss how it modifies the leading-order Nambu sum rule result and its relevance for the qualitative description of the spectrum.

Fermionic decays of NMSSM Higgs bosons under LHC 13 TeV constraints

This paper investigates the impact of the recent LHC constraints on the Higgs sector in the semi-constrained version of the Next-to-Minimal Supersymmetric Standard Model. Our analysis focuses on the parameter space for which the value of the Higgs doublet-singlet coupling, λ, is large as possible, while the ratio between the vacuum expectation values of the two Higgs doublets, tanβ, is small as possible. Under the current constraints, we present the possible fermionic decay channels and reduced cross-section into fermions final states for the lightest neutral Higgs bosons in the NMSSM, (h1,h2, and a1). We found that the branching ratios of the non SM-like Higgs (a1 and h2) into a pair of bottom quarks are near 90% level when the Higgs mass below 400 GeV. Moreover, the branching ratio of h2/a1→tt¯ can reach unity for all mass ranges when these bosons are mostly singlet.

Flux-mediated dark matter

We propose a new mechanism to communicate between fermion dark matter and the Standard Model (SM) only through the four-form flux. The four-form couplings are responsible for the relaxation of the Higgs mass to the correct value and the initial displacement of the reheating pseudo-scalar field from the minimum. We show that the simultaneous presence of the pseudo-scalar coupling to fermion dark matter and the flux-induced Higgs mixing gives rise to unsuppressed annihilations of dark matter into the SM particles at present, whereas the direct detection bounds from XENON1T can be avoided. We suggest exploring the interesting bulk parameter space of the model for which dark matter annihilates dominantly into a pair of singlet-like scalars with similar mass as for dark matter.