Supersymmetric Model Higgs Bosons Research Articles

A closer look at non-decoupling D -terms

Non-Decoupling D-Terms are an attractive possibility to enhance the tree-level mass of the standard model like Higgs boson in supersymmetric models. We discuss here for the case of a new Abelian gauge group two effects usually neglected in literature: (i) the size of the additional radiative corrections to the Higgs mass due to the presence of the new gauge coupling, and (ii) the impact of gauge kinetic mixing. It is shown that both effects reduce to some extent the positive effect of the non-decoupling D-terms on the Higgs mass.

Invisible decays of low mass Higgs bosons in supersymmetric models

The discovery of a 126 GeV Higgs-like scalar at the LHC along with the nonobservation of the supersymmetric particles has in turn led to constraining various supersymmetric models through the Higgs data. We here consider the case of both the minimal supersymmetric standard model (MSSM) as well its extension containing an additional chiral singlet superfield, the next-to-minimal or nonminimal supersymmetric standard model (NMSSM). A lot of work has been done in the context of the lightest scalar of these models being identified as the 126 GeV state discovered at the LHC. We here, however, concentrate on the case where we identify the second lightest Higgs boson as the 126 GeV state discovered at the CERN LHC and consider the invisible decays of the low mass Higgs bosons in both the MSSM and NMSSM. In the case of the MSSM we consider $H\ensuremath{\approx}126\text{ }\text{ }\mathrm{GeV}$ and $h\ensuremath{\approx}98\text{ }\text{ }\mathrm{GeV}$, known as the nondecoupling regime, whereas in the case of the NMSSM ${h}_{2}\ensuremath{\approx}126\text{ }\text{ }\mathrm{GeV}$, with ${m}_{{h}_{1}}$ and ${m}_{{a}_{1}}$ varying depending on the parameter space. We find that, in the case of the MSSM with universal boundary conditions at the grand unified theory (GUT) scale, it is not possible to have light neutralinos leading to the decay channel $H\ensuremath{\rightarrow}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}$. The invisible decay mode is allowed in the case of certain $SO(10)$ and ${E}_{6}$ grand unified models with large representations and nonuniversal gaugino masses at the GUT scale. In the case of the NMSSM, for the parameter space considered it is possible to have the invisible decay channel with universal gaugino masses at the GUT scale. We furthermore consider the most general case, with ${M}_{1}$ and ${M}_{2}$ as independent parameters for both the MSSM and NMSSM. We isolate the regions in parameter space in both cases where the second lightest Higgs boson has a mass of 126 GeV and then concentrate on the invisible decay of Higgs bosons to lighter neutralinos. The other nonstandard decay mode of the Higgs boson is also considered in detail. The invisible Higgs branching ratio being constrained by the LHC results, we find that, in this case with the second lightest Higgs boson being the 126 GeV state, more data from the LHC are required to constrain the neutralino parameter space, compared to the case when the lightest Higgs boson is the 126 GeV state.

Invisible decays of the lightest Higgs boson in supersymmetric models

We consider supersymmetric models in which the lightest Higgs scalar can decay invisibly consistent with the constraints on the $126$~GeV state discovered at the CERN LHC. We consider the invisible decay in the minimal supersymmetric standard model~(MSSM), as well its extension containing an additional chiral singlet superfield, the so-called next-to-minimal or nonminimal supersymmetric standard model~(NMSSM).We consider the case of MSSM with both universal as well as nonuniversal gaugino masses at the grand unified scale, and find that only an $E_6$ grand unified model with unnaturally large representation can give rise to sufficiently light neutralinos which can possibly lead to the invisible decay $h^0 \rightarrow \tilde \chi_1^0 \tilde \chi_1^0$. Following this, we consider the case of NMSSM in detail, where also we find that it is not possible to have the invisible decay of the lightest Higgs scalar with universal gaugino masses at the grand unified scale. We delineate the regions of the NMSSM parameter space where it is possible to have the lightest Higgs boson to have a mass of about $126$ GeV, and then concentrate on the region where this Higgs can decay into light neutralinos, with the soft gaugino masses $M_1$ and $M_2$ as two independent parameters, unconstrained by grand unification. We also consider, simultaneously, the other important invisible Higgs decay channel in the NMSSM, namely the decay into the lightest CP odd scalars, $h_1 \to a_1 a_1$, which is studied in detail. With the invisible Higgs branching ratio being constrained by the present LHC results, we find that $\mu_{eff} < 170$~GeV and $M_1 < 80$~GeV is disfavored in NMSSM for fixed values of the other input parameters. The dependence of our results on the parameters of NMSSM is discussed in detail.

Supersymmetric QCD corrections to Higgs pair production from bottom quark fusion

We present a complete next-to-leading order calculation for the total cross section for inclusive Higgs pair production via bottom-quark fusion at the CERN Large Hadron Collider in the minimal supersymmetric standard model and the minimal supergravity model. We emphasize the contributions of squark and gluino loops and the decoupling properties of our results for heavy squark and gluino masses. The enhanced couplings of the $b$ quark to the Higgs bosons in supersymmetric models with large $\mathrm{tan}\ensuremath{\beta}$ yield large next-to-leading order supersymmetry QCD corrections in some regions of parameter space.

A more flavored Higgs boson in supersymmetric models

A More flavored Higgs boson arises when the flavor structure encoded in SUSY extensions of the SM is transmited to the Higgs sector. The flavor-Higgs transmition mechanism can have a radiative or mixing origin, as it is illustrated with several examples, and can produce interesting Higgs signatures that can be probed at future high-energy colliders. Within the MSSM, the flavor mediation mechanism can be of radiative type, as it is realized trhough gaugino-slepton loops, which transmit the flavor structture of the soft-breaking sector to the Higgs bosons. In particular we focus on evaluating the contributions from the general trilinear terms to the lepton flavor violating Higgs (LFV) vertices. On the other hand, as an example of flavor mediation through mixing, we discuss an E_6 inspired multi-Higgs model, with an abelian flavor symmetry, where LFV as well as lepton flavor conserving Higgs effects are found to arise, though in this case at tree-level. We find that Tevatron and LHC can provide information on the flavor structure of these models through the detection of the LFV higgs mode h-> tau+mu, while NLC can perform high-precision measurements of the LFC mode h-> tau tau.

Generations of Higgs bosons in supersymmetric models

We examine extensions of the MSSM with more than one generation of Higgs bosons. If one assumes that a symmetry eliminates the tree-level FCNC, then the extra scalar bosons do not acquire VEVs, do not couple to fermions and do not mix with the ordinary Higgs bosons; the lightest is absolutely stable. The two lightest neutral scalars, $\phi_S$, and $\phi_P$, are degenerate in mass, and the mass difference between those and the lightest charged scalar, $\phi_+$, is calculated. For most of the parameter space, the charged scalar is between a hundred MeV and a few GeV heavier than the neutral scalars. The $\phi_+$ will decay at the vertex; the signature for this decay will be like that of a chargino with a nearly degenerate undetected neutralino. Next, the possibility that the symmetry that eliminates FCNC is a flavor symmetry is discussed. In an example, the U(2) model, tree-level FCNC processes can be calculated in terms of quark masses. The strongest constraint on this model is from $D-\bar{D}$ mixing, which should be within an order of magnitude of the current bound.

Reach of CERN LEP2 and Fermilab Tevatron upgrades for Higgs bosons in supersymmetric models

Luminosity upgrades of the Fermilab Tevatron pbar-p collider have been shown to allow experimental detection of a Standard Model (SM) Higgs boson up to $m_{H_{SM}}\sim 120$ GeV via $WH_{SM} \to \ell\nu b\bar{b}$ events. This limit nearly saturates the parameter space for many models of weak scale supersymmetry (SUSY) with a minimal particle content. It is therefore interesting to examine the SUSY Higgs reach of future Tevatron experiments. Contours are presented of Higgs boson reach for CERN LEP2 and Tevatron luminosity upgrades for three models of weak scale SUSY: the Minimal Supersymmetric Standard Model (MSSM), the minimal Supergravity model (mSUGRA) and a simple Gauge Mediated SUSY Breaking Model (GMSB). In each case we find a substantial gain in reach at the Tevatron with integrated luminosity increasing from 10 fb^{-1} to 25-30 fb^{-1}. With the larger integrated luminosity, a Higgs search at the Tevatron should be able to probe essentially the entire parameter space of these models. While a discovery would be very exciting, a negative result would severely constrain our ideas about how weak scale supersymmetry is realized.

Light charged Higgs bosons in supersymmetric models

We point out that present experimental limits from searches for neutral Higgs bosons at LEP already imply stringent lower bounds on the mass of the charged Higgs boson in the Minimal Supersymmetric Standard Model (MSSM); these bounds are especially severe for low values of tan β (tan β≤3), where the H + t ̄ b coupling is large. However, these indirect constraints are much weaker in simple extensions of the MSSM Higgs sector involving the introduction of an extra U(1) gauge group or an extra SU(2)× U(1) Y Higgs singlet field; in the latter case charged Higgs bosons can even be light enough to be pair produced at LEP.

Limits on the mass of the lightest Higgs boson in supersymmetric models

In supersymmetric models extended with a gauge singlet, the mass of the lightest Higgs boson has contributions proportional to the adimensional coupling $\ensuremath{\lambda}.$ In minimal scenarios, the requirement that this coupling remains perturbative up to the unification scale constrains $\ensuremath{\lambda}$ to be smaller than $\ensuremath{\approx}0.7.$ We study the maximum value of $\ensuremath{\lambda}$ consistent with a perturbative unification of the gauge couplings in models containing nonstandard fields at intermediate scales. These fields appear in scenarios with gauge mediation of supersymmetry breaking. We find that the presence of extra fields can raise the maximum value of $\ensuremath{\lambda}$ up to 19%, increasing the limits on the mass of the lightest Higgs boson from 135 GeV to 155 GeV.

Supersymmetric-Higgs-boson hadroproduction and decays including radiative corrections.

Radiative corrections can produce substantial changes in the masses, production cross sections, and decay branching fractions of Higgs bosons in supersymmetric models, which can greatly modify their experimental detectability. We study variations in the expected event rates at $\mathrm{pp}$ supercolliders caused by radiative effects from the full one-loop effective potential in the minimal model, for the $\mathrm{CP}$-even bosons $h$ and $H$. We note that the masses of $h$, $H$, and the $\mathrm{CP}$-odd boson $A$ can simultaneously fall in the intermediate mass range ${M}_{Z}&lt;m&lt;2{M}_{Z}$ that is difficult to explore at hadron supercolliders. We calculate the one-loop corrections to the triple neutral-Higgs-boson couplings that enter into the $h$ and $H$ branching fractions. We evaluate the $\mathrm{pp}\ensuremath{\rightarrow}h(H)$ production cross sections at the Superconducting Super Collider energy, together with the principal $h$ and $H$ decay fractions, and compare them with standard-model results. We find that the $h$ and $H$ Higgs-boson signals in the $\ensuremath{\gamma}\ensuremath{\gamma}$ and ${\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decay channels are generally less favorable than for the standard-model Higgs-boson search, except in some special cases.

Higgs bosons in supersymmetric models (III). Decays into neutralinos and charginos

We give explicit formulae for the decays of the Higgs bosons of the minimal supersymmetric model to neutralinos and charginos. The important features of these decays are illustrated and their phenomenological implications discussed. Particular attention is given to the decays of heavy Higgs bosons (with masses larger than m Z) which can only be observed at a future supercollider. When phase-space allowed, Higgs decays into neutralinos and charginos are at least as important as, and often dominate, other types of Higgs decay modes, such as WW, ZZ, and heavy quark (or lepton) pairs.

Invisible decays of Higgs bosons in supersymmetric models.

We point out that the dominant decay of the light scalar Higgs boson in a supersymmetric model may be into a pair of the lightest neutralinos (assumed to be the lightest supersymmetric particles), which would result in an invisible final state. Thus, in the search at the Stanford Linear Collider and the CERN collider LEP for a Higgs scalar produced in association with a real or virtual Z boson, it is important not to cut out events with significant missing energy recoiling against the Z.

Higgs bosons in supersymmetric models (II). Implications for phenomenology

We discuss a wide range of phenomenological issues involving the production and decay of Higgs bosons. We focus on a minimal two-doublet supersymmetry model with soft supersymmetry breaking.

Higgs bosons in supersymmetric models (I)

We describe the properties of Higgs bosons in a class of supersymmetric theories. We consider models in which the low-energy sector contains two weak complex doublets and perhaps one complex gauge-singlet Higgs field. Supersymmetry is assumed to be either softly or spontaneously broken, thereby imposing a number of restrictions on the Higgs boson parameters. We elucidate the Higgs boson masses and present Feynman rules for their couplings to the gauge bosons, fermions and scalars of the theory. We also present Feynman rules for vertices which are related by supersymmetry to the above couplings. Exact analytic expressions are given in two useful limits — one corresponding to the absence of the gauge-singlet Higgs field and the other corresponding to the absence of a supersymmetric Higgs mass term.