We examine various direct and indirect constraints on the lepton-specific two-Higgs doublet model and scrutinize the property of the Higgs bosons in the allowed parameter space. These constraints come from the precision electroweak data, the direct search for Higgs boson, the muon anomalous magnetic moment, as well as some theoretical consistency requirements. We find that in the allowed parameter space the CP-odd Higgs boson A is rather light (m_A < 30 GeV with 95% possibility), which is composed dominantly by the leptonic Higgs and decays dominantly into τ^+ τ^-; while the SM-like Higgs boson h (responsible largely for electroweak symmetry breaking) decays dominantly in the mode h->A A->4 τwith a large decay width, which will make the Higgs discovery more difficult at the LHC. Whereas, this scenario predicts a branching ratio Br(Z->τ^+ τ^- A) ranging from 10^{-5} to 10^{-4}, which may be accessible at the the GigaZ option of the ILC.
In this talk, we report unitarity constraints and phenomenological studies at the Large Hadron Collider for the extra Higgs bosons of a Composite 2-Higgs Doublet Model.
We study the inclusion of new heavy fermions on complex scalar dark matter (DM) phenomenology within gauged two Higgs doublet model (G2HDM). We find that for DM mass above 1 TeV, heavy quarks coannihilations into the Standard Model (SM) quarks and gluons dominate the thermally-averaged cross section relevant for the relic abundance of complex scalar DM. We demonstrate that the effects of QCD Sommerfeld correction as well as QCD bound state formation in determining the DM relic are negligible. We show that the allowed parameter space is significantly constrained by the current PLANCK relic dens…
We make a phenomenological study of a model with two inert doublets plus one Higgs doublet (I(2+1)HDM) which is symmetric under a Z$_2$ group, preserved after Electro-Weak Symmetry Breaking (EWSB) by the vacuum alignment $(0,0,v)$. This model may be regarded as an extension to the model with one inert doublet plus one Higgs doublet (I(1+1)HDM), by the addition of an extra inert scalar doublet. The neutral fields from the two inert doublets provide a viable Dark Matter (DM) candidate which is stabilised by the conserved $Z_2$ symmetry. We study the new Higgs decay channels offered by the scalar…
We study the dark matter phenomenology of scotogenic frameworks through a rather illustrative model extending the Standard Model by scalar and fermionic singlets and doublets. Such a setup is phenomenologically attractive since it provides the radiative generation of neutrino masses, while also including viable candidates for cold dark matter. We employ a Markov Chain Monte Carlo algorithm to explore the associated parameter space in view of numerous constraints stemming from the Higgs mass, the neutrino sector, dark matter, and lepton-flavour violating processes. After a general discussion of…
The most general two-Higgs doublet model (2HDM) includes potentially large sources of flavor changing neutral currents (FCNCs) that must be suppressed in order to achieve a phenomenologically viable model. The flavor alignment ansatz postulates that all Yukawa coupling matrices are diagonal when expressed in the basis of mass-eigenstate fermion fields, in which case tree-level Higgs mediated FCNCs are eliminated. In this work, we explore models with the flavor alignment condition imposed at a very high energy scale, which results in the generation of Higgs-mediated FCNCs via renormalization gr…
We investigate the phenomenology of Composite 2-Higgs Doublet Models (C2HDMs) of various Yukawa types based on the global symmetry breaking $SO(6)\to SO(4)\times SO(2)$. The kinetic term and the Yukawa Lagrangian are constructed in terms of the pseudo Nambu-Goldstone Boson (pNGB) matrix and a 6-plet of fermions under $SO(6)$. The scalar potential is assumed to be the same as that of the Elementary 2-Higgs Doublet Model (E2HDM) with a softly-broken discrete $Z_2$ symmetry. We then discuss the phenomenological differences between the E2HDM and C2HDM by focusing on the deviations from Standard Mo…
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 …
Yukawa txtures and charged Higgs boson phenomenology in the type-III two-Higgs-doublet model
我们讨论了假设一个四零汤川纹理的带电希格斯玻色子玻色子的性质的一般2-希格斯双重模型的第三类的背景下的影响。我们首先详细分析带电的希格斯玻色子玻色子与重夸克的耦合及其衰变模式。生产的带电希格斯玻色子也是敏感的修改其耦合，使我们也评估所产生的影响，顶部衰变$t \to b H^{+}$以及“直接”$c\bar{b}\to H^++c. c.$和“间接”$q\bar q,gg\to \bar t b H^++c. c.$生产。在大型强子对撞机上存在着几个$H^\pm$产生和衰变通道，使人们能够区分这样一个模型和替代的2-希格斯双态场景。
We consider the two Higgs doublet model (2HDM) along with a generation of vector-like lepton doublet and singlet to explain the observed discrepancies in the electron and muon anomalous magnetic moments. The type-X (lepton-specific) 2HDM can allow a light pseudo-scalar which is known to explain the muon anomalous magnetic moment at two-loop. Such a light particle induces a sizable negative contribution to the electron anomalous magnetic moment at one-loop in the presence of vector-like leptons evading all the experimental constraints.
The implementation of maximally restrictive texture zeros in the leptonic sector is investigated in the context of two-Higgs-doublet models with Majorana neutrinos. After analyzing all maximally restrictive pairs of leptonic mass matrices with zero entries, we conclude that there are only four texture combinations that are compatible with observations at 3 sigma confidence level and can be implemented through Abelian symmetries in a two-Higgs-doublet model. The compatibility of these textures with current constraints on lepton-flavor-violating processes is also studied. The ultraviolet complet…
We investigate the radiative generation of lepton masses and mixing angles in the Standard Model extended by one right-handed neutrino and one extra Higgs doublet. We assume approximate rank-1 Yukawa couplings at a high energy scale and we calculate the one loop corrected charged lepton and neutrino mass matrices at the low energy scale. We find that quantum effects generate, for typical high energy parameters, a hierarchy between the muon and the tau mass, a hierarchy between the solar and the atmospheric mass splittings, and a pattern of leptonic mixing angles in qualitative agreement with e…
We discuss how charged-lepton masses can be induced in multi-Higgs doublet models (NHDMs) through renormalization group running of Yukawa couplings. Examples of electron and muon mass generation are presented within scenarios with two- and three-Higgs-doublet models. We also show that quantum corrections to the Yukawa couplings can be naturally of the same order as the tree-level values. The impact of such corrections in NHDMs with right-handed neutrinos is briefly commented.
There exist about $3.7σ$ positive and $2.4σ$ negative deviations in the muon and electron anomalous magnetic moments ($g-2$). Also, some ratios for lepton universality in $τ$ decays have almost $2σ$ deviations from the Standard Model. In this paper, we propose a lepton-specific inert two-Higgs-doublet model. After imposing all the relevant theoretical and experimental constraints, we show that these lepton anomalies can be explained simultaneously in many parameter spaces with $m_H > 200$ GeV and $m_A~(m_{H^\pm})> 500$ GeV for appropriate Yukawa couplings between leptons and inert Higgs. The k…
We consider the doublet-triplet fermionic model in the scheme of the custodial limit when the dark matter (DM) candidate is pure doublet and lies at the electroweak scale. This scheme, despite being an appealing and promising DM model, is severely constrained by the interplay between the DM relic density constraint and the LHC measurement of the Higgs diphoton decay rate. In this work, the DM relic density is considered to arise from either a nonstandard cosmology scenario or as a part of a larger sector encompassing other DM particles, this in order to saturate the observed relic abundance. F…
We propose a 2-Higgs doublet model where the symmetry is extended by $S_{3}\otimes Z_{3}\otimes Z_{3}^{\prime }\otimes Z_{14}$ and the field content is enlarged by extra $SU(2)_{L}$ singlet scalar fields. $S_3$ makes the model predictive and leads to viable fermion masses and mixing. The observed hierarchy of the quark masses arises from the $Z_{3}^{\prime }$ and $Z_{14}$ symmetries. The light neutrino masses are generated through a type I seesaw mechanism with two heavy Majorana neutrinos. In the lepton sector we obtain mixing angles that are nearly tri-bi-maximal, in an excellent agreement w…
We study the phenomenology of d=7 1-loop neutrino mass models. All models in this particular class require the existence of several new $SU(2)_L$ multiplets, both scalar and fermionic, and thus predict a rich phenomenology at the LHC. The observed neutrino masses and mixings can easily be fitted in these models. Interestingly, despite the smallness of the observed neutrino masses, some particular lepton number violating (LNV) final states can arise with observable branching ratios. These LNV final states consists of leptons and gauge bosons with high multiplicities, such as 4l+4W, 6l+2W, etc. …
In the first part of this thesis, we consider an extension to the Standard Model composed by a Massive Vector Doublet under SU(2)L and a Left-handed Heavy Neutral Lepton. We study the production of these exotic leptons with a Same Flavor Opposite Sign standard lepton pair, and jets. We establish limits on the parameter space considering previous searches in this final state. After the limit definition, we study a modification on the event selection criteria in order to increase the possibility of probing these new particles at the Large Hadron Collider. Finally, we perform a parameter scan con…
The type X (lepton-specific) two-Higgs-doublet model at large $\tanβ$ becomes leptophilic and thus allows a light pseudoscalar $A$ accommodating the observed muon $g-2$ deviation without conflicting with various hadronic constraints. On the other hand, it is strongly constrained by leptonic precision observables such as lepton universality test in the neutral and charged currents. Treating all the lepton universality data in a consistent way, we show how the current data constrain the parameter space of $m_A$ and $\tanβ$ for given degenerate masses of heavy Higgs bosons $H$ and $H^\pm$. While …
Combining the multi-lepton searches at the LHC, we study the possibilities of accommodating the new data of muon and electron $g-2$ anomalies in the lepton-specific inert two-Higgs-doublet model. We take the heavy CP-even Higgs as the 125 GeV Higgs, and find the muon and electron $g-2$ anomalies can be explained simultaneously in the region of 5 GeV $< m_h<60$ GeV, 200 GeV $<m_A< 620$ GeV, 190 GeV $<m_{H^\pm}< 620$ GeV for appropriate Yukawa couplings between leptons and inert Higgs. Meanwhile, the model can give a better fit to the data of lepton universality in $τ$ decays than the SM. Furthe…
We study the most popular scalar extension of the Standard Model, namely the Two Higgs doublet model, extended by a complex triplet scalar (2HDMcT). Such considering model with a very small vacuum expectation value, provides a solution to the massive neutrinos through the so-called type II seesaw mechanism. We show that the 2HDMcT enlarged parameter space allow for a rich and interesting phenomenology compatible with current experimental constraints. In this paper the 2HDMcT is subject to a detailed scrutiny. Indeed, a complete set of tree level unitarity constraints on the coupling parameters…
