Non-standard Higgs Bosons Research Articles

Discovering a light Higgs boson with light

We evaluate the prospects for detecting a non-standard light Higgs boson with a significant branching ratio to two photons, in run II of the Fermilab Tevatron. We derive the reach for several channels: $2\ensuremath{\gamma}$ inclusive, $2\ensuremath{\gamma}+1$ jet, and $2\ensuremath{\gamma}+2$ jets. We present the expected run II limits on the branching ratio of $\stackrel{\ensuremath{\rightarrow}}{h}\ensuremath{\gamma}\ensuremath{\gamma}$ as a function of the Higgs boson mass, for the case of ``bosonic,'' as well as ``top-color'' Higgs bosons.

Search for a nonstandard Higgs boson in diphoton events atpp¯collisions

We estimate the attainable limits on the coupling of a nonstandard Higgs boson to two photons taking into account the data collected by the Fermilab collaborations on diphoton events. We based our analysis on a general set of dimension-6 effective operators that give rise to anomalous couplings in the bosonic sector of the standard model. If the coefficients of all ``blind'' operators have the same magnitude, indirect bounds on the anomalous triple vector-boson couplings can also be inferred, provided there is no large cancellation in the Higgs-gamma-gamma coupling.

Trilepton Higgs boson signal at hadron colliders

Determining the origin of electroweak symmetry breaking will be one of the primary functions of high energy colliders. We point out that most Higgs boson searches pursued at hadron colliders require Yukawa interactions either in the production or the decay of a Higgs boson. We propose a trilepton Higgs boson search based only upon the gauge interactions of the Higgs. This strategy can be utilized successfully for the standard model (SM) Higgs boson as well as non-standard Higgs bosons which break electroweak symmetry but have little to do with fermion mass generation. The trileptons come from Wh production followed by Wh -> WWW^(*) -> 3l decays. A SM Higgs trilepton signal would be difficult to detect at the Tevatron collider: with 100 fb^{-1} of data, only a $3\sigma$ signal above background can be achieved after cuts if 140 GeV < mh < 175 GeV. Some discrimination of signal over background can be gained by analyzing the opposite sign dilepton pT distributions. At the LHC with 30 (100) fb^{-1} a clear discovery above the $5\sigma$ level is possible for a Higgs mass in the range 140-185 (125-200) GeV. Prospects for a trilepton Higgs discovery are greatly improved for models with non-standard Higgs sectors where a Higgs boson couples preferentially to vector bosons rather than to fermions.

Precision observables in SU(2) × U(1) models with an additional Higgs triplet

Electroweak precision observables are calculated at complete one-loop order in the extension of the standard model by an extra Higgs triplet, where the ϱ-parameter can be different from unity already at the tree level. One additional data point is required for fixing the input parameters. In the on-shell renormalization scheme the leptonic mixing angle sin 2 θ e at the Z peak is chosen, together with the conventional input α, M z , G μ , m t . The calculated observables depend on the mass of the doublet Higgs boson H 0 and on the masses of the extra non-standard Higgs bosons as free parameters. The predictions of the standard model and the triplet model coincide for all observables in the experimental range of the top mass. In the triplet model, all observables which show a dependence on the doublet Higgs mass M H 0 are consistent with a low value of M H 0 .

Electroweak radiative corrections toγγ→W+W−in the two-Higgs-doublet model

Electroweak radiative one-loop corrections to the process $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{W}^{+}{W}^{\ensuremath{-}}$ with photon and W-boson polarizations are calculated within the two-Higgs-doublet model extension of the standard model, and the relevant analytical results for the nonstandard Higgs bosons contributions to the helicity amplitudes are given. The relative difference between the predictions of the two-Higgs-doublet model and minimal standard model for a light salar ${M}_{{H}_{1}}$ and heavy ${M}_{{H}_{2}}$ and ${M}_{\ensuremath{\Phi}}$ easily exceed $\ifmmode\pm\else\textpm\fi{}20%$ for ${W}_{T}{W}_{T}$ pair production in the central angular region at high energy, and even larger for ${W}_{L}{W}_{L}$ pair production. The angular dependence corrections owing to the nonstandard Higgs boson get larger, where box diagrams constitute the dominant part of the radiative corrections.

Studying Higgs pair production in the process gamma gamma -->H0H0 in the two-Higgs-doublet model.

In the two-Higgs-doublet model the complete nonstandard Higgs boson helicity amplitudes for the Higgs boson pair production process $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{H}_{0}{H}_{0}$ is calculated and explicit formulas for nonstandard Higgs boson contributions to the helicity amplitudes are given. It is shown that the cross section is in the range of 0.03-30 pb at $\sqrt{s}=1$ TeV, for Higgs boson masses of $350&lt;{M}_{{H}_{0}}&lt;490$ GeV in monochromatic $\ensuremath{\gamma}\ensuremath{\gamma}$ collisions. The angular distribution for Higgs pair production is strongly peaked in the forward and backward directions. In particular the angular dependence for Higgs pair production is due to the nonstandard Higgs boson getting larger where the box diagrams constitute the dominant part of the differential cross section. For studying heavy Higgs pair production the use of circularly polarized photon beams with equal helicities is advantageous.

Search for neutral Higgs boson production through the process e +e − → Z ∗ H 0

The results of the searches for neutral Higgs boson production in the process e +e − → Z ∗ H 0 are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z 0 decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L. These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e +e − → Z ∗h 0 are set. A lower limit of 66.7 GeV at 95% C.L. is obtained for the case where the Higgs decays into an invisible final state.

Electroweak radiative corrections tott¯→H0H0in the two-Higgs-doublet model

Electroweak radiative one-loop corrections to Higgs boson pair production in tt\ifmmode\bar\else\textasciimacron\fi{} fusion processes are calculated in the two-Higgs-doublet extension of the standard model. The numerical size of the nonstandard corrections is discussed for the process tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}${\mathit{H}}_{0}$${\mathit{H}}_{0}$. The relative difference between the predictions of the two-Higgs-doublet model and the minimal standard model for a light scalar ${\mathit{M}}_{{\mathit{H}}_{1}}$ and heavy ${\mathit{M}}_{{\mathit{H}}_{2}}$ and ${\mathit{M}}_{\mathrm{\ensuremath{\Phi}}}$ easily exceeds -10% in the forward and backward directions. In particular the angular-dependence corrections owing to the nonstandard Higgs bosons get larger where the box and cubic Higgs boson vertex corrections constitute the dominant part of the radiative corrections. \textcopyright{} 1996 The American Physical Society.

THE SEARCH FOR NONSTANDARD HIGGS BOSONS WITH BIG YUKAWA COUPLING CONSTANTS AT FNAL AND LHC

We discuss the phenomenology of many Higgs doublet model—the model where each Higgs doublet couples with its own quark and lepton with relatively big Yukawa coupling constants. Namely, we investigate the discovery potential of the Higgs bosons at LHC and find lower mass limits on nonstandard Higgs bosons from FNAL data. We find that it is possible to discover such Higgs bosons at LHC with the masses up to 5 TeV.

Profile of a nonstandard Higgs boson at the CERN LHC.

In a wide class of extensions of the Standard Model there is a scalar resonance with the quantum numbers of the usual Higgs boson but with different couplings to fermions and gauge bosons. Using an effective Lagrangian description, we examine the phenomenology of such a generic nonstandard Higgs boson at the LHC. In particular, we determine the circumstances under which such a particle can be observed in its $ZZ$ decay mode and distinguished from the Higgs boson of the Standard Model. We briefly comment on the energy scale effectively probed at the LHC, if the nonstandard nature of an observed Higgs particle can be asserted.

Phenomenology of a nonstandard Higgs boson in WLWL scattering.

In this paper we consider the phenomenology of a ``non-standard'' Higgs Boson in longitudinal gauge-Boson scattering. First, we present a composite Higgs model (based on an $SU(4)/Sp\,(4)$ chiral-symmetry breaking pattern) in which there is a non-standard Higgs Boson. Then we explore, in a model-independent way, the phenomenology of such a non-standard Higgs by calculating the chiral logarithmic corrections to longitudinal gauge scattering. This calculation is done using the Equivalence theorem and the Higgs is treated as a scalar-isoscalar resonance coupled to the Goldstone Bosons of the \mbox{$SU(2)_{L} \times SU(2)_{R}/SU(2)_{V}$} chiral symmetry breaking. We show that the most important deviation from the one Higgs-doublet standard model is parameterized by one unknown coefficient which is related to the Higgs width. The implications for future hadron colliders are discussed.

Phenomenology of a non-standard Higgs

The one-Higgs-doublet standard model is necessarily incomplete because of the triviality of the scalar symmetry-breaking sector. If the Higgs mass is approximately 600 GeV or higher, there must be additional dynamics at a scale Λ which is less than a few TeV. In this case the properties of the Higgs resonance can differ substantially from those predicted by the standard model. In this letter we construct an effective Lagrangian description of a theory with a non-standard Higgs boson and analyze the features of a theory with such a resonance coupled to the Goldstone bosons of the breaking of SU(2) × U(1). This Lagrangian describes the most general theory in which the Higgs and the Goldstone bosons are the only particles with a mass small compared to Λ. We compute the leading corrections to the decay width of the Higgs boson and the contribution to the Peskin-Takeuchi parameter S and present results for the corrections to Goldstone boson scattering. We find that the most prominent effects are due to one new parameter, which is directly related to the Higgs boson width.

An unambiguous search for a light Higgs boson

A search for light Higgs bosons has been performed in an electron beam-dump experiment. No positive signal is observed which allows us to reject at 90% CL the existence of a standard Higgs in the range from 1.2 to 52 MeV. Non-standard Higgs bosons are also excluded in a large range of couplings. This search relies on the well controlled and calculable process of bremsstrahlung from electrons in the Coulomb field of large Z nuclei. Both production and decay are governed by the single coupling constant of Higgs to electrons.

Two-photon decay widths of Higgs bosons in minimal broken supersymmetry

The two-photon decay widths of nonstandard Higgs bosons are studied in a minimal broken-supersymmetry model. For two-Higgs-doublet models in general, a large enhancement of these widths relative to the standard model is possible. However, we find for the case studied that a severe upper bound on this possible enhancement is imposed by the supersymmetry features of the model. With only the t quark as the heaviest fermion we find a two-photon width of 100 keV for a 160-GeV/${c}^{2}$ scalar Higgs boson is possible. The corresponding width for a pseudoscalar is 60 keV.

Nonstandard-Higgs-scalar- and pseudoscalar-boson production in ep and e+e- colliders.

Nonstandard Higgs bosons in the mass range 40--150 GeV/${c}^{2}$ are studied for two-Higgs-doublet extensions of the standard electroweak model. Upper bounds on production rates are compared for ep and ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ colliders. Under favorable conditions our calculations indicate that about 100 events per year production rates at the DESY ep collider HERA for nonstandard Higgs bosons are obtainable. Electron-positron annihilations give smaller rates but cleaner signals.

Nonstandard Higgs bosons as a source of monojets.

Nonstandard Higgs-boson models are examined as a potential source for events with large missing Pt of the type recently seen by the UA1 group at CERN.Received 4 February 1985DOI:https://doi.org/10.1103/PhysRevD.32.86©1985 American Physical Society