Limits to possible scalar-boson mass and coupling from e +e − collisions

We discuss phenomenological consequences of requiring the cancellation of one-loop quadratic divergences in corrections to scalar masses within Two-Higgs-Doublet Models (2HDM). It is shown that the Inert Doublet Model (IDM) can not accommodate the requirement of the cancellation. A general 2HDM is also analyzed taking into account existing experimental constraints. Allowed regions in the parameter space, permitting the above cancellation, are determined. A degeneracy between masses of scalar bosons is observed for tanbeta \gsim 40. The possibility for CP violation in the scalar potential is discussed and regions of tanbeta-M_{H^\pm} with substantial amount of CP violation are determined. In order to provide a source for dark matter in a minimal manner, a scalar gauge singlet is introduced and discussed. The model allows to ameliorate the little hierarchy problem by lifting the minimal scalar Higgs boson mass and by suppressing the one-loop quadratic corrections to scalar masses. The cutoff originating from the naturality arguments is therefore lifted to \gsim 15 TeV depending on the mass of the lightest scalar.

One-boson-exchange potential model for the Λp interaction (II)

Scalar composite boson masses have been computed in QCD and technicolor theories with the help of the homogeneous Bethe-Salpeter equation, resulting in a scalar mass that is twice the dynamically generated fermion or technifermion mass (m(dyn)). We show that in the case of walking (or quasiconformal) technicolor theories, where the mdyn behavior with the momenta may be quite different from the one predicted by the standard operator product expansion, this result is incomplete and we must consider the effect of the normalization condition of the Bethe-Salpeter equation to determine the scalar masses. We compute the composite Higgs boson mass for several groups with technifermions in the fundamental and higher dimensional representations and comment about the experimental constraints on these theories, which indicate that models based on walking theories with fermions in the fundamental representation may, within the limitations of our approach, have masses quite near the actual direct exclusion limit.

Pseudo-Hermitian system is a class of non-Hermitian system with Hamiltonian satisfying the condition η−1H†η = H. We develop the in-in and Schwinger Keldysh formalism to calculate cosmological correlators for pseudo-Hermitian systems. We study a model consists of massive symplectic fermions coupled to the primordial curvature perturbation. The three-point function for the primordial curvature perturbation is computed up to one-loop and compared to earlier work where the loop correction comes from a massive scalar boson. The two results differ by a minus sign. Therefore, the one loop correction to the three-point function cannot be used to distinguished scalar bosons and symplectic fermions. To conclude, we discuss possibilities where the scalar bosons and symplectic fermions may be distinguished.

The scalar Higgs boson mass in a Technicolor model was obtained by Elias and Scadron with the analysis of an homogeneous Bethe–Salpeter equation (BSE), however it was performed before the most recent developments of walking gauge theories. It was not observed in their work that dynamically generated technifermion mass may vary according to the theory dynamics that forms the scalar bound state. This will be done in this work and we also call attention that their calculation must change to take into account the normalization condition of the BSE. We compute the width of the composite boson and show how the gauge group and fermion content of a technicolor theory can be inferred from the measurement of the mass and width of the scalar boson.

Gauge boson masses in the 3D, SU(2) gauge-Higgs model

Tuning effect in particle masses manifests itself in integer relations between lepton masses and parameters of the pion (its mass, the mass splitting and fπ). It involves parameters of constituent quark model and basic values of the Standard Model: masses of vector and scalar bosons, QED parameters and the top quark mass. The role of nuclear data is discussed.

Weak interaction gauge symmetry breaking can be generated by radiative corrections in a spontaneously broken supergravity theory, provided the top quark is heavy enough. In one class of such theories the weak Higgs vacuum expectation values are determined by dimensional transmutation a la Coleman‐Weinberg, and may be considerably larger than the magnitudes of susy breaking mass parameters. In this scenario mt≥65 GeV, the supersymmetric partners of known particles may have masses ≪mW, the mass of the lighter neutral scalar Higgs boson is determined by radiative corrections, and there is some variant of a light pseudoscalar axion. In contrast to conventional Coleman‐Weinberg models, the weak phase transition is second order and there is no likelihood of excess entropy production.

Fermion masses and Fayet-Iliopoulos terms in string theory

We propose a description of the Higgs boson as top-antitop quark bound state within a nonlocal relativistic quark model of Nambu - Jona-Lasinio type. In contrast to model with local four-fermion interaction, the mass of the scalar bound state can be lighter than the sum of its constituents. This is achieved by adjusting the interaction range and the value of the coupling constant to experimental data, for both the top quark mass and the scalar Higgs boson mass, which can simultaneously be described.

Recently proposed models of weak interactions based on spontaneously broken gauge symmetry contain additional interactions arising from exchange of the scalar Higgs particles and/or neutral vector bosons. Further, higher-order corrections are finite, and therefore should be taken seriously. We investigate what constraints on parameters of models are imposed by consideration of Higgs-particle exchange and of higher-order effects in $K$ decays. To bring out the main points we shall focus mainly on the SO(3) models of Georgi and Glashow. In the 5-quark version of the Georgi-Glashow model, the Higgs scalar couples strongly to ($\overline{\ensuremath{\lambda}}\mathfrak{N}$), and to ($\overline{e}e$), so that processes such as ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+e+\overline{e}$ decay can occur already in lowest order. Thus a stringent lower bound (${m}_{\ensuremath{\varphi}}\ensuremath{\ge}10$ GeV) is imposed on the mass of the scalar particle. For the process ${K}_{L}\ensuremath{\rightarrow}\ensuremath{\mu}+\overline{\ensuremath{\mu}}$, which occurs in second order, we find the amplitude to be of order ${G}_{F}\ensuremath{\alpha}{sin\ensuremath{\theta}}_{C}$ and independent of the value of ${M}_{W}$. This is clearly in contradiction with experiment and rules out the 5-quark version. We analyze also an 8-quark version of the model, in which extra quarks are used to suppress the amplitudes for ${K}_{L}\ensuremath{\rightarrow}\ensuremath{\mu}+\overline{\ensuremath{\mu}}$ and ${K}^{0}\ensuremath{\leftrightarrow}{\overline{K}}^{0}$: The amplitudes are of order ${G}_{F}\ensuremath{\alpha}(\frac{\ensuremath{\Delta}{m}^{2}}{{{M}_{W}}^{2}})$, where $\ensuremath{\Delta}{m}^{2}$ is the difference between the squared masses of "charmed" and "uncharmed" quarks. It is also shown that in this version single-scalar-particle exchange is altogether forbidden and the constraint on ${m}_{\ensuremath{\varphi}}$ is accordingly eliminated. Constraints similar to those found for the Georgi-Glashow models also apply to other spontaneously broken gauge models of weak interactions.

In two recently proposed supersymmetric extended electroweak gauge models, the reduced Higgs sector at the 100 GeV energy scale consists of only two doublets, but they have quartic scalar couplings different from those of the minimal supersymmetric standard model. In the SU(2)*SU(2)*U(1) model, there is an absolute upper bound of about 145 GeV on the mass of the lightest neutral scalar boson. In the SU(3)*U(1) model, there is only a parameter-dependent upper bound which formally goes to infinity in a particular limit.

A supersymmetric standard model with heavier scalar supersymmetric particles has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the standard model like Higgs boson with mass around 125 GeV, which is strongly favored by the LHC experiment, can be realized. However, in this scenario the scalar particles are too heavy to be produced at the LHC. In addition, if the scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too short to be measured. Therefore, it is hard to probe the scalar particles at a collider. However, a detailed study of the gluino decay reveals that two body decay of the gluino carries important information on the scalar scale. In this paper, we propose a test of this scenario by measuring the decay pattern of the gluino at the LHC.

We discuss first-order electroweak phase transition in models with extended Higgs sectors for the case with relatively heavy additional scalar bosons. We first show that, by the combination of the sphaleron decoupling condition, perturbative unitarity and vacuum stability, mass upper bounds on additional scalar bosons can be obtained at the TeV scale even at the alignment limit where the lightest Higgs boson behaves exactly like the SM Higgs boson at tree level. We then discuss phenomenological impacts of the case with the additional scalar bosons with the mass near 1 TeV. Even when they are too heavy to be directly detected at current and future experiments at hadron colliders, the large deviation in the triple Higgs boson coupling can be a signature for first-order phase transition due to quantum effects of such heavy additional Higgs bosons. On the other hand, gravitational waves from the first-order phase transition are found to be weaker in this case as compared to that with lower masses of additional scalar bosons.

It has been argued by Pisarski and Wilczek that finite temperature restoration of the chiral symmetry SU(Nf) x SU(Nf) is first-order for Nf >=3. This type of chiral symmetry with a large Nf may appear in the Higgs sector if one considers models such as walking technicolor theories. We examine the first-order restoration of the chiral symmetry from the point of view of the electroweak phase transition. The strength of the transition is estimated in SU(2) x U(1) gauged linear sigma model by means of the finite temperature effective potential at one-loop with the ring improvement. Even if the mass of the neutral scalar boson corresponding to the Higgs boson is larger than 114 GeV, the first-order transition can be strong enough for the electroweak baryogenesis, as long as the extra massive scalar bosons (required for the linear realization) are kept heavier than the neutral scalar boson. Explicit symmetry breaking terms reduce the strength of the first-order transition, but the transition can remain strongly first-order even when the masses of pseudo Nambu-Goldstone bosons become as large as the current lower bound of direct search experiments.