Higgs Scalars Research Articles

Asymptotically free four-fermion interactions and electroweak symmetry breaking

We investigate the fermions of the standard model without a Higgs scalar. Instead, we consider a non-local four-quark interaction in the tensor channel which is characterized by a single dimensionless coupling $f$. Quantization leads to a consistent perturbative expansion for small $f$. The running of $f$ is asymptotically free and therefore induces a non-perturbative scale $\Lambda_{ch}$, in analogy to the strong interactions. We argue that spontaneous electroweak symmetry breaking is triggered at a scale where $f$ grows large and find the top quark mass of the order of $\Lambda_{ch}$. We also present a first estimate of the effective Yukawa coupling of a composite Higgs scalar to the top quark, as well as the associated mass ratio between the top quark and the W boson.

Inflation with non-minimal gravitational couplings in supergravity

We explore in the supergravity context the possibility that a Higgs scalar may drive inflation via a non-minimal coupling to gravity characterised by a large dimensionless coupling constant. We find that this scenario is not compatible with the MSSM, but that adding a singlet field (NMSSM, or a variant thereof) can very naturally give rise to slow-roll inflation. The inflaton is necessarily contained in the doublet Higgs sector and occurs in the D-flat direction of the two Higgs doublets.

Phenomenological Aspects of the Next-to-Minimal Supersymmetric Standard Model

The motivations for the NMSSM are reviewed, and possible unconventional signals for Higgs and sparticle production at the LHC are discussed. In the presence of a light pseudoscalar, the SM-like Higgs scalar can decay dominantly into a 4-tau final state. In the fully constrained NMSSM with mSUGRA-like soft SUSY breaking terms, the correct dark matter relic density is obtained for a singlino-like LSP which modifies considerably all sparticle decay chains.

On the radiative corrections to the neutral Higgs boson masses in the NMSSM

We provide a full one-loop calculation of the self energies and tadpoles of the neutral Higgs bosons of the NMSSM. In addition, we compute the two-loop O ( α t α s + α b α s ) corrections to the neutral Higgs boson masses in the effective potential approximation. With respect to earlier calculations, the newly-computed corrections can account for shifts of a few GeV in the light scalar and pseudoscalar masses, and they can also sizeably affect the mixing between singlet and MSSM-like Higgs scalars. Taking these corrections into account will be crucial for a meaningful comparison between the MSSM and NMSSM predictions for the Higgs sector.

Is ``just-so'' Higgs splitting needed fort−b−τ Yukawa unified SUSY GUTs?

Recent renormalization group calculations of the sparticle mass spectrum in the Minimal Supersymmetric Standard Model (MSSM) show that t−b−τ Yukawa coupling unification at MGUT is possible when the mass spectra follow the pattern of a radiatively induced inverted scalar mass hierarchy. The calculation is entirely consistent with expectations from SO(10) SUSY GUT theories, with one exception: it seems to require MSSM Higgs soft term mass splitting at MGUT, dubbed ``just-so Higgs splitting'' (HS) in the literature, which apparently violates the SO(10) gauge symmetry. Here, we investigate three alternative effects: i). SO(10) D-term splitting, ii). inclusion of right hand neutrino in the RG calculation, and iii). first/third generation scalar mass splitting. By combining all three effects (the DR3 model), we find t−b−τ Yukawa unification at MGUT can be achieved at the 2.5% level. In the DR3 case, we expect lighter (and possibly detectable) third generation and heavy Higgs scalars than in the model with HS. In addition, the light bottom squark in DR3 should be dominantly a right state, while in the HS model, it is dominantly a left state.

Bs,d−B¯s,dmixings andb→q(γ,ll¯)decays in private Higgs model

We study the low energy phenomena induced by the lightest charged Higgs in the private Higgs model, in which each quark flavor is associated with a Higgs doublet. We show that the couplings of the charged Higgs scalars to fermions are fixed and the unknown parameters are only the masses and mixing elements of the charged Higgs scalars. As the charged Higgs masses satisfy with ${M}_{b}<{M}_{c}\ensuremath{\ll}{M}_{s}\ensuremath{\ll}{M}_{d,u}$, processes involving $B$-meson are expected to be the ideal places to test the private Higgs model. In particular, we explore the constraints on the model from experimental data in $B$ physics, such as the branching ratio (BR) and $CP$ asymmetry of $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$, ${B}_{d,s}\mathrm{\text{\ensuremath{-}}}{\overline{B}}_{d,s}$ mixings and the BR for $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$. We illustrate that the sign of the Wilson coefficient for $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ can be different from that in the standard model, while this flipped sign can be displayed by the forward-backward asymmetry of $B\ensuremath{\rightarrow}V{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ with $V$ a vector meson. We also demonstrate that ${B}_{d,s}\mathrm{\text{\ensuremath{-}}}{\overline{B}}_{d,s}$ mixings and their time-dependent $CP$ asymmetries are negligible small and the BR of $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ can have a more strict bound than that of $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$.

Is it possible to estimate the Higgs mass from the CMB power spectrum?

General Relativity and Standard Model are considered as a theory of dynamical scale symmetry with definite initial data compatible with the accepted Higgs mechanism. In this theory the Early Universe behaves like a factory of electroweak bosons and Higgs scalars, and it gives a possibility to identify three peaks in the Cosmic Microwave Background power spectrum with the contributions of photonic decays and annihilation processes of primordial Higgs, W and Z bosons in agreement with the QED coupling constant, Weinberg’s angle, and Higgs’ particle mass of about 118 GeV.

Higgs funnel region of supersymmetric dark matter for smalltanβand renormalization group effects on pseudoscalar Higgs boson with scalar mass nonuniversality

A non-universal scalar mass supergravity type of model is explored where the first two generation of scalars and the third generation of sleptons may be very massive. Lighter or vanishing third generation of squarks as well as Higgs scalars at the unification scale cause the radiative electroweak symmetry breaking constraint to be less prohibitive. Thus, both FCNC/CP-violation problems as well as the naturalness problem are within control. We identify a large slepton mass effect in the RGE of $m_{H_D}^2$ (for the down type of Higgs) that may turn the later negative at the electroweak scale even for a small $\tan\beta$. A hyperbolic branch/focus point like effect is found for $m_A^2$ that may result in very light Higgs spectra. The lightest stable particle is dominantly a bino that pair annihilates via Higgs exchange, giving rise to a WMAP satisfied relic density region for all $\tan\beta$. Detection prospects of such LSPs in the upcoming dark matter experiments both of direct and indirect types (photon flux) are interesting. The Higgs bosons and the third generation of squarks are light in this scenario and these may be easily probed besides charginos and neutralinos in the early runs of LHC.

Higgs triplets, decoupling, and precision measurements

Electroweak precision data has been extensively used to constrain models containing physics beyond that of the standard model. When the model contains Higgs scalars in representations other than $SU(2)$ singlets or doublets, and hence $\ensuremath{\rho}\ensuremath{\ne}1$ at tree level, a correct renormalization scheme requires more inputs than the three needed for the standard model. We discuss the connection between the renormalization of models with Higgs triplets and the decoupling properties of the models as the mass scale for the scalar triplet field becomes much larger than the electroweak scale. The requirements of perturbativity of the couplings and agreement with electroweak data place strong restrictions on models with Higgs triplets. Our results have important implications for Little Higgs type models and other models with $\ensuremath{\rho}\ensuremath{\ne}1$ at tree level.

Radiative seesaw in left-right symmetric model

There are some radiative origins for the neutrino masses in the conventional left-right symmetric models with the usual bidoublet and triplet Higgs scalars. These radiative contributions could dominate over the tree-level seesaw and could explain the observed neutrino masses.

Higgs decays and brane gravi-vectors

Higgs boson decays in flexible brane world models with stable, massive gravi-vectors are considered. Such vectors couple bilinearly to the standard model fields through either the standard model energy-momentum tensor, the weak hypercharge field strength, or the Higgs scalar. The role of the coupling involving the extrinsic curvature is highlighted. It is found that within the presently allowed parameter space, the decay rate of the Higgs into two gravi-vectors (which would appear as an invisible Higgs decay) can be comparable to the rate for any of the standard model decay modes.

Higgs-Higgsino-gaugino induced two loop electric dipole moments

We compute the complete set of Higgs-mediated chargino-neutralino two-loop contributions to the electric dipole moments of the electron and neutron in the minimal supersymmetric standard model (MSSM). We study the dependence of these contributions on the parameters that govern $CP$-violation in the MSSM gauge-gaugino-Higgs-Higgsino sector. We find that contributions mediated by the exchange of $W{H}^{\ifmmode\pm\else\textpm\fi{}}$ and $Z{A}^{0}$ pairs, where ${H}^{\ifmmode\pm\else\textpm\fi{}}$ and ${A}^{0}$ are the charged and $CP$-odd Higgs scalars, respectively, are comparable to or dominate over those mediated by the exchange of neutral gauge bosons and $CP$-even Higgs scalars. We also emphasize that the result of this complete set of diagrams is essential for the full quantitative study of a number of phenomenological issues, such as electric dipole moment searches and their implications for electroweak baryogenesis.

Neutrino mass and low-scale leptogenesis in a testable SUSY [formula omitted] model

It is shown that a supersymmetric SO(10) model extended with fermion singlets can accommodate the observed neutrino masses and mixings as well as generate the desired lepton asymmetry in concordance with the gravitino constraint. A necessary prediction of the model is near-TeV scale doubly-charged Higgs scalars which should be detectable at the LHC.

Same-sign single dilepton productions at the LHC

We examine the same-sign single dilepton productions of ℓi±ℓj±(ℓi,j=e,μ) with missing energy in high-energy proton–proton collisions at the Large Hadron Collider (LHC) in models with doubly charged Higgs scalars as well as heavy Majorana neutrinos. We demonstrate that these spectacular productions can be detected at the LHC for a class model in which the doubly charged Higgs scalars couple only to the right-handed charged leptons. The ranges of the possible doubly charged Higgs masses and mixings to observe the processes at the LHC are discussed.

Erratum:A4flavor symmetry and neutrino phenomenology [Phys. Rev. D77, 073008 (2008)

It has been shown that tribimaximal mixing can be obtained by some particular breaking pattern of the $A_4$ symmetry, wherein the extra $A_4$ triplet Higgs scalars pick up certain fixed vacuum expectation value (VEV) alignments. We have performed a detailed analysis of the different possible neutrino mass matrices within the framework of the $A_4$ model. We take into account all possible singlet and triplet Higgs scalars which leave the Lagrangian invariant under $A_4$. We break $A_4$ spontaneously, allowing the Higgs to take any VEV in general. We show that the neutrino mixing matrix deviates from tribimaximal, both due to the presence of the extra Higgs singlets, as well as from the deviation of the triplet Higgs VEV from its desired alignment, taken previously. We solve the eigenvalue problem for a variety of these illustrative cases and identify the ones where one obtains exact tribimaximal mixing. All such cases require fine-tuning. We show which neutrino mass matrices would be strongly disfavored by the current neutrino data. Finally, we study in detail the phenomenology of the remaining viable mass matrices and establish the deviation of the neutrino mixing from tribimaximal, both analytically as well as numerically.

Refining the predictions of supersymmetricCP-violating models: A top-down approach

We explore in detail the consequences of the CP-violating phases residing in the supersymmetric and soft SUSY breaking parameters in the approximation that family flavour mixings are ignored. We allow for non-universal boundary conditions and in such a consideration the model is described by twelve independent CP-violating phases and one angle which misaligns the vacuum expectation values (VEVs) of the Higgs scalars. We run two-loop renormalization group equations (RGEs), for all parameters involved, including phases, and we properly treat the minimization conditions using the one-loop effective potential with CP-violating phases included. We show that the two-loop running of phases may induce sizable effects for the electric dipole moments (EDMs) that are absent in the one-loop RGE analysis. Also important corrections to the EDMs are induced by the Higgs VEVs misalignment angle which are sizable in the large tan β region. Scanning the available parameter space we seek regions compatible with accelerator and cosmological data with emphasis on rapid neutralino annihilations through a Higgs resonance. It is shown that large CP-violating phases, as required in Baryogenesis scenarios, can be tuned to obtain agreement with WMAP3 cold dark matter constraints, EDMs and all available accelerator data, in extended regions of the parameter space which may be accessible to LHC.

A4flavor symmetry and neutrino phenomenology

It has been shown that tribimaximal mixing can be obtained by some particular breaking pattern of the ${A}_{4}$ symmetry, wherein the extra ${A}_{4}$ triplet Higgs scalars pick up certain fixed vacuum expectation value (VEV) alignments. We have performed a detailed analysis of the different possible neutrino mass matrices within the framework of the ${A}_{4}$ model. We take into account all possible singlet and triplet Higgs scalars which leave the Lagrangian invariant under ${A}_{4}$. We break ${A}_{4}$ spontaneously, allowing the Higgs to take any VEV in general. We show that the neutrino mixing matrix deviates from tribimaximal, both due to the presence of the extra Higgs singlets, as well as from the deviation of the triplet Higgs VEV from its desired alignment, taken previously. We solve the eigenvalue problem for a variety of these illustrative cases and identify the ones where one obtains exact tribimaximal mixing. All such cases require fine-tuning. We show which neutrino mass matrices would be strongly disfavored by the current neutrino data. Finally, we study in detail the phenomenology of the remaining viable mass matrices and establish the deviation of the neutrino mixing from tribimaximal, both analytically as well as numerically.

Multi-Higgs mass spectrum in gauge-Higgs unification

We study an $SU(2)$ supersymmetric gauge model in a framework of gauge-Higgs unification. Multi-Higgs spectrum appears in the model at low energy. We develop a useful perturbative approximation scheme for evaluating effective potential to study the multi-Higgs mass spectrum. We find that both tree-massless and massive Higgs scalars obtain mass corrections of similar size from finite parts of the loop effects. The corrections modify the multi-Higgs mass spectrum, and hence, the loop effects are significant in view of future verifications of the gauge-Higgs unification scenario in high-energy experiments.

CHIRAL FREEDOM AND THE SCALE OF WEAK INTERACTIONS

A second rank antisymmetric tensor field is proposed as an alternative to the Higgs scalar. No mass term is allowed by the symmetries. At the scale where the asymptotically free chiral couplings of the fermions grow large, condensates of top–antitop and bottom–antibottom may induce the spontaneous breaking of the electroweak gauge symmetry. This would solve the gauge hierarchy problem by dimensional transmutation, similar to QCD.

Leptogenesis, dark matter and Higgs phenomenology at TeV

We propose an interesting model of neutrino masses to realize leptogenesis and dark matter at the TeV scale. A real scalar is introduced to naturally realize the Majorana masses of the right-handed neutrinos. We also include a new Higgs doublet that contributes to the dark matter of the universe. The neutrino masses come from the vacuum expectation value of the triplet Higgs scalar. The right-handed neutrinos are not constrained by the neutrino masses and hence they could generate leptogenesis at the TeV scale without subscribing to resonant leptogenesis. In our model, all new particles could be observable at the forthcoming Large Hardon Collider or the proposed future International Linear Collider.