In type III seesaw utilized to explain the observed solar and atmospheric neutrino oscillations the Standard Model (SM) particle spectrum is extended by introducing three SU(2)_L triplet fermion fields. This can have important implications for the SM Higgs boson mass (M_H) bounds based on vacuum stability and perturbativity arguments. We compute the appropriate renormalization group equations for type III seesaw, and then proceed to identify regions of the parameter space such that the SM Higgs boson mass window is enlarged to 125 GeV < M_H < 174 GeV, with the type III seesaw scale close to TeV. We also display regions of the parameter space for which the vacuum stability and perturbativity bounds merge together for large neutrino Yukawa couplings. Comparison with type I seesaw is also presented.
Type-X two Higgs doublet model is known to explain the muon $g-2$ anomaly with a relatively light charged Higgs boson at large $\tanβ$. The light charged Higgs boson has been searched in the main $τν$ mode at the colliders. Invoking a scenario of inverse seesaw as the origin of neutrino masses and mixing, the charged Higgs boson can decay additionally to right-handed neutrinos which leads to interesting phenomenology. Considering generic lepton flavour violating signatures at the final states, a $5σ$ discovery can be achieved with the early data of LHC, at 14 TeV, for relatively large inverse …
We study parameters of an extended standard model. The neutrino sector is enlarged by one or two right-handed singlet fields and the Higgs sector contains one additional doublet. One-loop radiative corrections generate the mass for the light neutrino fields. The numerical analysis is performed varying the masses of heavy neutrinos and of the additional neutral Higgses. The parameters of the neutrino sector, allowing for the seesaw type-I mechanism, are restricted by experimental neutrino oscillation data. Both normal and inverted hierarchies of the light neutrino masses are discussed.
Type I Seesaw Mechanism, Lepton Flavour Violation and Higgs Decays
我们回顾和更新目前的唯象约束的最小I型跷跷板扩展的标准模型，其中新物理的内容可以在电弱尺度探测。在这类模型中，中微子Yukawa耦合的味结构由再现中微子振荡数据的要求决定。对跷跷板参数空间的最强约束是最近μ -> e γ衰变率的上限。非标准的希格斯玻色子玻色子衰变为轻中微子和重中微子的过程也可能提供对这些跷跷板情景的独立测试。
Higgs-mediated muon-electron conversion process in supersymmetric seesaw model
在超对称跷跷板模型中研究了Higgs交换图对轻子味破坏的μ子-电子转换过程的影响。这种贡献对于tan β的大值和中性重希格斯玻色子质量的小值是显著的，在这种情况下，B（mu N -> e N）/ B（mu -> e γ）的分支比的比率增强。我们还表明，转换分支比的靶原子的依赖性提供了希格斯交换图的大小上的信息。
The top-seesaw assisted technicolor (TC) model, which was proposed recently to explain the 126 GeV Higgs mass discovered by the Large Hadron Colliders (LHC), predicts light and heavy charged Higgs bosons in addition to the neutral Higgses. In this paper we will study the pair productions of the charged Higgs, proceeding through gluon-gluon fusion and quark-anti-quark annihilation, at the LHC in the frame of the top-seesaw assisted TC model. We find that in a large part of parameter space the production cross sections of the light charged Higgs pair at the LHC can be quite large compared with t…
We investigate the stability of Higgs potential in inverse seesaw models. We derive the full two-loop RGEs of the relevant parameters, such as the quartic Higgs self-coupling, taking thresholds into account. We find that for relatively large Yukawa couplings the Higgs quartic self-coupling goes negative well below the Standard Model instability scale $\sim 10^{10}$ GeV. We show, however, that the ``dynamical'' inverse seesaw with spontaneous lepton number violation can lead to a completely consistent and stable Higgs vacuum up to the Planck scale.
We show that simple extensions of two Higgs doublet models consisting of new heavy neutrinos and a singly charged Higgs boson singlet can successfully explain the experimental data on muon and electron anomalous magnetic moments thanks to large chirally-enhanced one-loop level contributions. These contributions arise from the large couplings of inverse seesaw neutrinos with singly charged Higgs bosons and right-handed charged leptons. The regions of parameter space satisfying the experimental data on $(g-2)_{e,μ}$ anomalies allow heavy singly charged Higgs boson masses above the TeV scale, pro…
Two Higgs Doublet Models (2HDM) are popular extensions of the Standard Model for several reasons, but do not explain neutrino masses. In this work, we investigate how one can incorporate neutrino masses within the framework of the 2HDM-U(1), where U(1) is an abelian gauge symmetry used to nicely address the absence of flavor changing neutral currents in 2HDM. In particular, we explore realizations of the type I and type II seesaw since they are mechanisms that we dote on for being able to generate elegantly small active neutrino masses. We show that one can build several models featuring type …
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 restriction…
It has recently been pointed out that the underlying symmetry of dark matter may well be $U(1)_χ$ (coming from $SO(10) \to SU(5) \times U(1)_χ$) with the dark parity of any given particle determined by $(-1)^{Q_χ+2j}$, where $Q_χ$ is its $U(1)_χ$ charge and $j$ its spin angular momentum. Armed with this new insight, previous simple models of dark matter are reinterpreted, and a novel idea is proposed that light seesaw dark matter exists in analogy to light neutrinos and is produced by the rare decay of the standard-model Higgs boson.
We introduce a new class of Composite Higgs models in which electroweak symmetry is broken by a seesaw-like mechanism. If a global symmetry is broken sequentially at different scales, two sets of pseudo-Goldstone bosons will arise, one set being typically heavier than the other. If two Composite Higgs doublets mix, then the mass-squared of the lighter state can be driven negative, and induce EWSB. We illustrate with the example $SO(6) \rightarrow SO(5) \rightarrow SO(4)$, and derive an estimate of the light Higgs potential. We find that the introduction of an extra scale can ease many of the t…
We investigate charged lepton flavor violating (CFLV) processes in the `neutrinophilic Higgs+seesaw model', in which right-handed neutrinos couple only with an extra Higgs field which develops a tiny VEV and the right-handed neutrinos also have Majorana mass. The model realizes a seesaw mechanism around TeV scale without extremely small Dirac Yukawa couplings. A phenomenological feature of the model is CFLV processes induced by loop diagrams of the charged scalar particles and heavy neutrinos. Therefore, first we constrain the model's parameter space from the search for $μ\to eγ$. Next, we pre…
We propose a radiative seesaw model based on a modular $A_4$ symmetry, which has good predictability in the lepton sector. We execute a numerical analysis to search for parameters that satisfy the experimental constraints such as those from neutrino oscillation data and lepton flavor violations. Then, we present several predictions in our model that originate from the modular symmetry at a fixed point as well as fundamental region of $τ$.
Neutrino mass generation through the Higgs mechanism not only suggests the need to reconsider the physics of electroweak symmetry breaking from a new perspective, but also provides a new theoretically consistent and experimentally viable paradigm. We illustrate this by describing the main features of the electroweak symmetry breaking sector of the simplest type-II seesaw model with spontaneous breaking of lepton number. After reviewing the relevant "theoretical" and astrophysical restrictions on the Higgs sector, we perform an analysis of the sensitivities of Higgs boson searches at the ongoin…
We study parameters of an extension of the Standard Model. The neutrino sector is enlarged by one right-handed singlet field, allowing for the seesaw mechanism type-I, and the Higgs sector contains one additional doublet, which contributes to light neutrino masses through one-loop radiative corrections. Employing an approximation for the effective light neutrino mass matrix we express the masses of the light neutrinos analytically, allowing us to parametrize the Yukawa couplings to neutrinos by the experimental measurements on the neutrino sector and only two free parameters. We focus on a CP-…
Alternative renormalizable minimal non-SUSY SO(10) GUT model is proposed. Instead of a ${\bf 126}$-dimensional Higgs field, a ${\bf 120}$-dimensional Higgs filed is ntroducedin addition to a ${\bf 10}$-dimensional Higgs field and plays a crucial role to reproduce the realistic charged fermion mass matrices. With contributions of ${\bf 120}$ Higgs field, the original Witten's scenario of inducing the right-handed Majorana neutrino mass through 2-loop diagrams becomes phenomenologically viable. This model inherits the nice features of the conventional renormalizable minimal SO(10) GUT model with…
We examine the simplest realization of the linear seesaw mechanism within the Standard Model gauge structure. Besides the standard scalar doublet, there are two lepton-number-carrying scalars, a nearly inert SU2 doublet and a singlet. Neutrino masses result from the spontaneous violation of lepton number, implying the existence of a Nambu-Goldstone boson. Such "majoron" would be copiously produced in stars, leading to stringent astrophysical constraints. We study the profile of the Higgs bosons in this model, including their effective couplings to the vector bosons and their invisible decay br…
We propose a model for the vector-like lepton to explain the small muon mass by a seesaw mechanism, based on lepton-specific two Higgs doublet models with a local $U(1)'$ symmetry. There is no bare muon mass for a nonzero $U(1)'$ charge of the leptophilic Higgs doublet, so the physical muon mass is generated due to the mixing between the vector-like lepton and the muon after the leptophilic Higgs doublet and the dark Higgs get VEVs. In this scenario, the non-decoupling effects of the vector-like lepton give rise to leading contributions to the muon $g-2$, thanks to the light $Z'$ and the light…
We investigate the collider phenomenology of the scalar triplet particles in the Type-II seesaw model at a 100 TeV $pp$ collider. Depending on triplet vacuum expectation value $v_Δ$, the dominant discovery channels could be $H^{++} H^{--}$ and $H^{\pm\pm}H^\mp$. We find the $H^{\pm\pm}H^\mp\to W^\pm W^\pm h W^\mp/\ell^\pm \ell^\pm h W^\mp$ channels are promising for both model discovery at relatively large $v_Δ$ and determination of the Higgs portal couplings $λ_4$ and $λ_5$. We also find that these two channels are complementary to indirect determination of $λ_4$ from future precise measureme…
We consider the production of a single Standard Model (SM) Higgs boson ($h^0$) in association with a photon at the future Linear collider (LC) in the context of a type-II seesaw model. The type-II seesaw model extends the SM particle content by adding one triple Higgs where its Higgs coupling is a key parameter of the scalar potential triggering the electroweak symmetry-breaking mechanism in the SM. It is a well motivated model since it provides neutrino masses and mixing. The LC presents a particularly interesting possibility to probe Higgs couplings due to the clean beams in the initial stat…
The scotogenic type I and type III seesaw models are good candidates to explain the existence of neutrino masses and dark matter simultaneously. However, since triplet fermions have SU(2) gauge interaction, they cannot be out of equilibrium before the electroweak symmetry breaking. Thus, leptogenesis seems to be difficult within a framework of the pure type III seesaw model. Some extension seems to be required to solve this fault. A model extended by introducing a singlet fermion could be such a simple example. If the singlet fermion is in the thermal equilibrium even for its extremely small n…
Sensitivity to the Higgs Sector of SUSY-Seesaw Models in the Lepton Flavour Violating tau-->mu f0(980) decay
本文研究了超对称-跷跷板模型下的轻子味破坏半轻子τ-> mu f0（980）衰变，其中MSSM谱被三个右手中微子及其超对称伴子扩展，并利用跷跷板机制产生中微子质量。我们估计了它通过希格斯介导通道tau--> mu H *--> mu f0（980）时的衰变率，其中H指CP偶MSSM希格斯玻色子玻色子h^0和H^0，轻子味破坏tau mu H顶点通过超对称环辐射产生。为了描述f0（980）介子，我们遵循手征约束的指导方针。作为我们的计算的一个含义，我们探讨了希格斯部门在这种衰变的敏感性，并将其与其他LFV τ衰变通道。我们对BR（tau--> mu f0（980））的预测与其目前非常具有竞争力的实验界的对抗，使我们提取了一些有趣的限制最相关的模型参数，特别是，tanbeta和m_{H^0}。
