In a general two Higgs doublet model (2HDM), the anomaly of muon anomalous magnetic moment (muon g-2) can be explained by $μ-τ$ flavor violating Yukawa couplings, motivated by the recent CMS excess in Higgs boson decay $h\rightarrow μτ$. We study Michel parameters for $τ$ decays $τ\rightarrow l ν\barν~(l=e,~μ)$ in the 2HDM with the lepton flavor violation, and show that they can be sensitive to the flavor structure as well as the Lorentz and chiral structures of the model. We find that the correction to the Michel parameter $ξ_μ$ in $τ\rightarrow μν\barν$ is correlated to the contribution to the muon g-2, and it can be as large as $10^{-4}-10^{-2}$ in the parameter region where the $μ-τ$ flavor violating Yukawa couplings explain the muon g-2 anomaly. Therefore the precision measurement of the Michel parameter at the level of $10^{-4}-10^{-2}$ would significantly probe the interesting parameter space for the solution to the muon g-2 anomaly.
Motivated by the recent CMS excess in a flavor violating Higgs decay $h \rightarrow μτ$ as well as the anomaly of muon anomalous magnetic moment (muon g-2), we consider a scenario where both the excess in $h \rightarrow μτ$ and the anomaly of muon g-2 are explained by the $μ-τ$ flavor violation in a general two Higgs doublet model. We study various processes involving $μ$ and $τ$, and then discuss the typical predictions and constraints in this scenario. Especially, we find that the prediction of $τ\rightarrow μγ$ can be within the reach of the Belle II experiment. We also show that the lepton…
We calculate the decay rate for inclusive $B \rightarrow τνX$ decays in a two Higgs doublet model using heavy quark expansion and operator product expansion. Combined with the recent measurement of Br($B \ra τνX$), we find a limit $\tan β< 0.58 m_H/\mbox{GeV}$ at 90\%\ C.L..
We perform a combined analysis of two stringent constraints on two Higgs doublet model, coming from the recently announced CLEO II bound on $B(b \rightarrow s γ)$ and $Z \rightarrow b \overline b$ and from the recent LEP data on the ratio $Γ(Z\rightarrow b\overline b)\over{Γ(Z\rightarrow hadrons)}$. We include one-loop vertex corrections to $Z \rightarrow b \overline b$ in the model. We find that although the CLEO II bound serves as the strongest constraint present in the charged Higgs sector of the model, the current LEP value for $R_b$ may also provide a further constraint for $\tanβ<1$.
The leptonic branching fractions of the tau lepton are sensitive to anomalous charged current interactions. We use recent experimental measurements to determine the weak charged current magnetic and electric dipole moments and the Michel parameter $η$ with unprecedented precision. These results are then used to constrain the tau compositeness scale and the allowed parameter space for Higgs doublet models.
In LEP searches for the neutral CP-odd scalar $A^0$ of a multi-Higgs doublet model, experimenters have searched for $Z\rightarrow h^0 A^0$ (where $h^0$ is the lightest CP-even scalar). No model-independent limit on the $A^0$ mass can be deduced from present data if $m_{h^0}>m_Z$. In this paper, we compute the rates for $Z\rightarrow A^0 A^0ν\barν$ and $e^+e^-\rightarrow A^0 A^0 Z$. Assuming that no light CP-even neutral scalars exist, the branching ratio for $Z\rightarrow A^0 A^0ν\barν$ is found to be less than $1.4\times10^{-8}$. At higher $e^+e^-$ center-of-mass energies, $σ(e^+e^-\rightarro…
In the most general two-Higgs doublet model with an approximate family symmetry and CP violation being originated solely from the relative phase of two vacuum expectation values, CP asymmetry in the decay $b\rightarrow sγ$ may arise from the CP violation of the charged Higgs boson interactions with fermions. This asymmetry may be larger than in the standard model and can lie between $10^{-2}$ and $10^{-1}$. The decay rate of $b\rightarrow sγ$ is allowed to be smaller or larger than in the standard model
In this paper we shall focus on the effects of concrete models such as SM and Model III of 2HDM on the polarized and unpolarized forward-backward asymmetries of $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ decays. The obtained results of these decay modes are compared to each other. Also, we obtain the minimum required number of events for detecting each asymmetry and compare them with the number of produced $B\bar{B}$ pairs at the LHC or supposed to be produced at the Super-LHC. At the end, we conclude that the study o…
We perform a combined analysis of two stringent constraints on the 2 Higgs doublet model, one coming from the recently announced CLEO II bound on $B(b \rightarrow s γ)$ and the other from the recent LEP data on $ε_b$. We have included one-loop vertex corrections to $Z \rightarrow b \overline b$ through $ε_b$ in the model. We find that the new $ε_b$ constraint excludes most of the less appealing window $\tanβ\lsim 1$ at $90\%$C.~L. for $m_t=150\GeV$. We also find that although $b \rightarrow s γ$ constraint is stronger for $\tanβ>1$, $ε_b$ constraint is stronger for $\tanβ\lsim 1$, and therefor…
We investigate the consequences of introducing a set of exotic doublet leptons which couple to the standard model leptons in a minimal way. Through these additional gauge invariant and renormalizable coupling terms, new sources of tree-level flavor changing currents are induced via mixing. In this work, we derive constraints on the parameters that govern the couplings to the exotic doublets by invoking the current low-energy experimental data on processes such as leptonic Z decays, $\ell \rightarrow 3 \ell'$, $\ell \rightarrow \ell' γ$, and $μ$-$e$ conversion in atomic nuclei. Moreover, we hav…
In this work, we introduce an extra singlet pseudoscalar into the Type-III two Higgs doublet model (2HDM) which is supposed to solve a series of problems in the modern particle-cosmology. With existence of a light pseudoscalar, the $h\rightarrowμτ$ excess measured at CMS and as well as the $(g-2)_μ$ anomaly could be simultaneously explained within certain parameter spaces that can also tolerate the data on the flavor-violating processes $τ\rightarrowμγ$ and Higgs decay gained at LHC. Within the same parameter spaces, the DM relic abundance is well accounted. Moreover, the recently observed Gal…
Models beyond the Standard Model with extra scalars have been highly motivated by the recent discovery of a Higgs boson. The Two Higgs Doublet Model Type III considers the most general case for the scalar potential, allowing mixing between neutral CP-even and CP-odd scalar fields. This work presents the results of the study on the $t\rightarrow cγ$ decay at one loop level if neutral flavor changing is generated by top-charm-Higgs coupling given by the Yukawa matrix. For instance, a value for the branching ratio $Br(t\rightarrow cγ)\sim 10^{-6}$ for $\tanβ=2.5$ and general neutral Higgs mixing …
The two Higgs doublet model emerges as a minimal scenario in which to address, at the same time, the $γγ$ excess at 750 GeV and the lepton flavour violating decay into $τ^\pm μ^\mp $ of the 125 GeV Higgs boson. The price to pay is additional matter to enhance the $γγ$ rate, and a peculiar pattern for the lepton Yukawa couplings. We add TeV scale vector-like fermions and find parameter space consistent with both excesses, as well as with Higgs and electroweak precision observables.
We study in next-to-leading order QCD hadronic penguin $B$ decays in the Standard and two-Higgs-doublet models. Although the gluonic penguin dominates, we find the electroweak contribution non-negligible. In the Standard Model, the branching ratio for $B \rightarrow X_s ϕ$ is predicted to be in the range $(0.6\sim 2)\times 10^{-4}$. The ranges of branching ratios for $B\rightarrow K ϕ$, $B\rightarrow K^*ϕ$, and $B_s\rightarrow ϕϕ$ are $(0.4\sim 2)\times 10^{-5}$, $(0.2\sim 1)\times 10^{-5}$, and $(0.15\sim 0.5)\times 10^{-5}$, respectively. The contribution from the charged Higgs boson in two …
A two Higgs doublet model (2HDM) is one of the minimal extensions of the Standard Model (SM), and it is well-known that the general setup predicts the flavor-violating phenomena, mediated by neutral Higgs interactions. Recently the CMS collaboration has reported an excess of the lepton-flavor-violating Higgs decay in $h \rightarrow μτ$ channel with a significance of 2.5 $ σ$. We investigate the CMS excess in a general 2HDM with tree-level Flavor Changing Neutral Currents (FCNCs), and discuss its impact on the other physical observations. Especially, we see that the FCNCs relevant to the excess…
Motivated by an anomaly in $R(D^{(*)})={\rm BR}(\bar{B}\rightarrow D^{(*)} τ^-\barν)/{\rm BR}(\bar{B}\rightarrow D^{(*)} l^-\barν)$ reported by BaBar, Belle and LHCb, we study $R(D^{(*)})$ in a general two Higgs doublet model (2HDM). Although it has been suggested that it is difficult for the 2HDM to explain the current world average for $R(D^{(*)})$, it would be important to clarify how large deviations from the standard model predictions for $R(D^{(*)})$ are possible in the 2HDM. We investigate possible corrections to $R(D^{(*)})$ in the 2HDM by taking into account various flavor physics con…
In this paper, we analyze the loop induced decays of neutral Higgs boson $ h $ into pairs of photons, gluons, and Z$ γ$ in 3-Higgs Doublet Models (3HDMs), where all the doublets have non-zero vacuum expectation values. In the 3HDM, there are contributions to these decays from loops of charged scalars $ H^{\pm}_{1,2} $ that are not present in the Standard Model. We find an enhancement in the channel $ h\rightarrow Zγ$ with respect to the Standard Model prediction in some parameter region while respecting constraints from the measurements of $ h\rightarrow γγ$ at the LHC. The charged Higgs boson…
The existence of a second Higgs doublet in Nature could lead to a cosmological first order electroweak phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We obtain the spectrum and properties of the new scalars $H_0$, $A_0$ and $H^{\pm}$ that signal such a phase transition, and show that the observation of the decay $A_0 \rightarrow H_0 Z$ at LHC would be a `smoking gun' signature of these scenarios. We analyze the LHC search prospects for this decay in the $\ell \ell b\bar{b}$ and $\ell \ell W^{+} W^{-}$ final states, arguing that current data may be s…
We present a complete one-loop computation of the $H^\pm \rightarrow W^\pm Z$ decay in the aligned two-Higgs-doublet model. The constraints from the electroweak precision observables, perturbative unitarity, vacuum stability and flavour physics are all taken into account along with the latest Large Hadron Collider searches for the charged Higgs. It is observed that a large enhancement of the branching ratio can be obtained in the limit where there is a large splitting between the charged and pseudo-scalar Higgs masses as well as for the largest allowed values of the alignment parameter $ς_u$. …
In this paper we analyze the dilepton mass square $q^2$ dependency of single lepton polarization asymmetries and CP violation for $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-, \ell=μ,τ)$ in the 2HDM context. Also, we study the averages of these asymmetries in the domain $4 m_{\ell}^2<q^2< (m_B-m_{{K}_0^{*}})^2$. Our study manifests that the investigation of the above-mentioned asymmetries for $\overline{B}\rightarrow \overline{K}_0^*(1430) \ell^+\ell^-$ processes could provide useful information for probing new Higgs bosons in the future B-physics experiments.
The latest LHC data confirmed the existence of a Higgs-like particle and made interesting measurements on its decays into $γγ$, $Z Z^\ast$, $W W^\ast$, $τ^+ τ^-$, and $b \bar{b}$. It is expected that a decay into $Z γ$ might be measured at the next LHC round, for which there already exists an upper bound. The Higgs-like particle could be a mixture of scalar with a relatively large component of pseudoscalar. We compute the decay of such a mixed state into $Z γ$, and we study its properties in the context of the complex two Higgs doublet model, analysing the effect of the current measurements on…
We discuss possible signatures of the $CP$-odd scalar of two-doublet models at the LHC. We find that the inclusive two-photon decay mode and the decay sequence $A^0 \rightarrow Zh, h \rightarrow γγ$, where $h$ is a $CP$-even neutral scalar, can give viable signals in fairly large and complementary regions of parameter space.
In a general two-scalar-doublet model without fermions, there is a unique source of CP violation, $ J_1 $, in the gauge interactions of the scalars. It arises in the mixing of the three neutral physical scalars $ X_1 $, $ X_2 $ and $ X_3 $. CP violation may be observed via different decay rates for $ X_1 \rightarrow H^+ W^- $ and $ X_1 \rightarrow H^- W^+ $ (or, alternatively, for $ H^+ \rightarrow X_1 W^+ $ and $ H^- \rightarrow X_1 W^- $ --- depending on which decays are kinematically allowed). I compute the part of those CP-violating decay-rate differences which is proportional to $ J_1 $. …
We study quark flavor violating interactions mediated by the Higgs boson $h$. We consider observables involving a third generation quark, of both the up and the down quark sectors, like $h\rightarrow bs$ and $t\rightarrow ch$. Using an effective field theory approach we systematically list all the possible tree-level ultraviolet completions, which comprise models with vector-like quarks and/or extra scalars. We provide upper bounds on the flavor violating transitions allowed by current limits stemming from low energy processes, such as meson mixing and $b \rightarrow s γ$. We find that scenari…
Latest CMS results on the upper limits on $σ_{H^\pm}$BR($H^\pm \rightarrow τ^\pmν)$ and $σ_{H^\pm}$BR($H^+ \rightarrow t\bar{b}$) for $\sqrt{s}=13$ TeV at an integrated luminosity of 35.9 fb$^{-1}$ are used to impose constraints on the charged Higgs $H^\pm$ parameters within the Two Higgs Doublet Model (2HDM). The 2HDM is the simplest extension of Standard Model (SM) under the same gauge symmetry to contain charged Higgs and is relatively less constrained compared to Minimal Supersymmetric Standard Model (MSSM). The latest results lead to much more stringent constraints on charged Higgs parame…
Type-Z models, where charged leptons, up type quarks, and down type quarks each couple to a different scalar, are only possible when there are three or more Higgs doublets. We consider the Type-Z three Higgs doublet model imposed by a softly broken $Z_3$ symmetry. We take into account all theoretical and experimental constraints, highlighting the importance of perturbative unitarity and bounded from below conditions that we develop here, and which have a strong impact on $B \rightarrow X_s γ$. Since there can be cancellations between the two charged Higgs in $B \rightarrow X_s γ$ (and in $h \r…
We analyze uncertainties in the theoretical prediction for the inclusive branching ratio $BR[B \rightarrow X_s γ]$. We find that the dominant uncertainty in the leading order expression comes from its $μ$-dependence. We discuss a next-to-leading order calculation of $B \rightarrow X_s γ$ in general terms and check to what extent the $μ$-dependence can be reduced in such a calculation. We present constraints on the Standard and Two-Higgs-Doublet Model parameters coming from the measurement of $b \rightarrow s γ$ decay. The current theoretical uncertainties do not allow one to definitively restr…
We perform a complete one-loop computation of the two-body flavour-changing top decays $t \rightarrow c h$ and $t \rightarrow c V$ ($V= γ, Z$), within the aligned two-Higgs-doublet model. We evaluate the impact of the model parameters on the associated branching ratios, taking into account constraints from flavour data and measurements of the Higgs properties. Assuming that the $125$~GeV Higgs corresponds to the lightest CP-even scalar of the CP-conserving aligned two-Higgs-doublet model, we find that the rates for such flavour-changing top decays lie below the expected sensitivity of the futu…
One-loop contributing for $A \rightarrow Z Z γ$ in the Two-Higgs-Doublet Model with Vector-Like Quarks
University of Science, Ho Chi Minh City（胡志明市科技大学）；Vietnam National University, Ho Chi Minh City（胡志明市越南国立大学）；Institute of Fundamental and Applied Sciences, Duy Tan University（大慈大学基础与应用科学研究所）；Faculty of Natural Sciences, Duy Tan University（大慈大学自然科学学院）；Eastern International University（东方国际大学）
该研究计算了双希格斯二重态模型加矢量-like夸克中 $A \rightarrow Z Z γ$ 的单圈衰变，发现矢量-like夸克可改变总率约5%，其分支比可达 $10^{-5}-10^{-4}$，未来缪子对撞机或可观测该效应。
We present numerical calculations of the partial width of the charged Higgs boson decay into a top quark, $H^- \rightarrow \bar{t} + b + X$, and the partial width of the top quark decay into a light charged Higgs boson $t \rightarrow H^+ + b + X$ at next-to-next-to-leading order (NNLO) in QCD, based on a factorization formula of the jet mass. The NNLO corrections significantly reduce the renormalization scale dependence of the partial decay width in both cases. We show relative size of the NNLO corrections for different charged Higgs boson masses and for different renormalization scales. The N…
We systematically analyse the gluonic penguin-induced charmless decays $B \ra K_Xϕ$($K_X$ denotes the meson state $s\bar q \;(q=u\ {\rm or}\ d)$ ), in the standard model and the two-Higgs-doublet model. These processes, being induced at one-loop level, are of great importance in measuring the virtual top quark effect in the standard model, and also in searching for the non-standard signals in the low energy region. It is shown that the QCD effect is also significant in these processes, as in the weak radiative processes $B \ra X_s γ$. We also show that the charged Higgs contribution can not pr…
We define and test $\mathrm{CP}$-even and $\mathrm{CP}$-odd partial differential widths for the process $τ\rightarrow Kππν_τ$ assuming that an intermediate heavy charged scalar contributes to the decay amplitude. Adopting a model-independent approach, we use a Monte Carlo simulation in order to study the number of events needed to recover information on the new physics from these observables. Our analysis of the $\mathrm{CP}$-odd observables indicates that the magnitude of $f_H η_P$, which is related to the new-physics contribution, can be recovered with an uncertainty smaller than $3%$ for $3…
In this talk I consider the current status of $B \rightarrow D^{(*)} τν$ decays in the context of two-Higgs-doublet models. The BaBar collaboration has reported an excess in semileptonic $b \rightarrow c τν$ transitions that has gathered recent interest as a possible signature of new physics. The sensitivity of these decays to tree-level charged Higgs boson contributions is discussed, taking into account the constraints from other semileptonic and leptonic meson decays in which the charged Higgs would enter at the same level.
We consider the radiative decay $b\rightarrow s γ$, and the correction to the $Zb\overline{b}$ vertex in technicolor models with scalars. In these models, the scalar develops a vacuum expectation value when the technifermions condense, and the ordinary fermions develop masses via Yukawa couplings. Since the symmetry breaking sector involves both a fundamental scalar doublet and an isotriplet of composite scalars (the technipions), the phenomenology associated with the charged scalars is similar to that found in a type-I two-Higgs doublet model. We show that the correction to the $Zb\overline{b…
We study the decay modes $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ within the frameworks of two-Higgs doublet models type-II and typ-III. We adopt in our study Soft Collinear Effective Theory as a framework for the calculation of the amplitudes. We derive the contributions of the charged Higgs mediation to the weak effective Hamiltonian governing the decay processes in both models. Moreover we analyze the effect of the charged Higgs mediation on the Wilson coefficients of the electrowek penguins and on the branching ratios of $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ decays. We show that w…
The rare decay $h \rightarrow Υγ$ has a very small rate in the Standard Model, due to a strong cancellation between the direct and indirect diagrams. Models with a changed $hbb$ coupling can thus lead to a great increase in this decay. Current limits on two Higgs doublet models still allow for the possibility that the $hbb$ coupling might have a sign opposite to the Standard Model; the so-called "wrong-sign". We show how $h \rightarrow Υγ$ can be used to put limits on the wrong-sign solutions.
Due to the large mass of top quark, CP violation in the top-quark decay is sensitive to the interactions mediated by Higgs bosons. We consider CP violation in $t\rightarrow W^+ b$ decay by calculating consistently in unitary gauge the CP-violating up-down asymmetry of the leptons from $W$ boson decays in $t\rightarrow W^+ b$, defined by Grzcadkowski and Gunion, in the two-Higgs doublet model with CP-violating neutral sector. The asymmetry is shown to be at most of the order of $(1-3)\times 10^{-4}$ for $\tanβ=1.0$, where $\tanβ$ is the ratio of vacuum expectation values for the two neutral Hig…
We discuss the production of a heavy neutral Higgs boson of a CP-conserving Two-Higgs-Doublet Model in gluon fusion and its decay into a four-fermion final state, $gg (\rightarrow VV) \rightarrow e^+e^-μ^+μ^-/e^+e^-ν_l\barν_l$. We investigate the interference contributions to invariant mass distributions of the four-fermion final state and other relevant kinematical observables. The relative importance of the different contributions is quantified for the process in the on-shell approximation, $gg\rightarrow ZZ$. We show that interferences of the heavy Higgs with the light Higgs boson and backg…
Probing first-generation doublet vector-like leptons via single production at the 3 TeV CLIC
Henan Institute of Science and Technology（河南科技学院）；Zhongyuan University of Science and Technology（中原工学院）；University of Southampton（南安普顿大学）；Uppsala University（乌普萨拉大学）
本研究在3 TeV CLIC上通过单产生过程，针对第一代二重态类矢量轻子开展信号与本底模拟及截断分析，获得不同积分亮度下的排除与发现灵敏度，可在宽质量范围灵敏探测该类轻子。
We present an alternative calculation for the leading Higgs mass dependent one--loop corrections to the standard model Lagrangian, using a background field technique. Cross--sections computed from our one--loop Lagrangian provide a check of and reproduce results already obtained in the existing literature using diagrammatic methods, as well as allowing an analysis of other processes involving longitudinally polarized $W^\pm$s and $Z^0$s. We concentrate on the processes $WW\rightarrow f\bar{f}$ and $f\bar{f}\rightarrow WW$. We extend our result to the case of a two Higgs doublet model, when one…
In this work, we present an analysis of a search for charged Higgs boson in the context of Two Doublet Higgs Model (2HDM) which is an extension of the Standard Model of particles physics. The 2HDM predicts by existence scalar sector with new five Higgs bosons, two of them are electrically charged and the other three Higgs bosons are neutral charged. Our analysis based on the Monte Carlo data produced from the simulation of 2HDM with proton antiproton collisions at the Tevatron $\sqrt{s}=1.96$ TeV (Fermi Lab) and proton proton collisions at the LHC $\sqrt{s}=14$ TeV (CERN) with final state incl…
The radiative corrections to the decay processes of the neutral ($CP$-even) Higgs boson ($H$) into a longitudinal gauge boson pair, {\it i.e.}, $H \rightarrow Z_{L}Z_{L}$ and $H \rightarrow W_{L}^{+}W_{L}^{-}$ are analyzed in the two-Higgs doublet model by assuming that all of the Higgs boson masses are much greater than the $W$ and $Z$ bosons'. These calculations are motivated to see if one could see potentially large virtual effects to these decay rates due to the charged and $CP$-odd neutral Higgs boson masses ($m_{G}$ and $m_{A}$, respectively) which are supposed to be larger than $m_{H}$.…
We present a likelihood analysis of the general two Higgs doublet model, using the most important currently measured flavour observables, in view of the anomalies in charged current tree-level and neutral current one-loop rare decays of $B$ mesons in $b\to c l \overlineν$ and $b\to sμ^{+}μ^{-}$ transitions, respectively. We corroborate that the model explains the latter and it is able to simultaneously fit the experimental values of the $R(D)$ ratio at $1σ$, but it can not accommodate the $R(D^{*})$ and $F_{L}(D^{*})$ observables. We find that the fitted values for the angular observables in $…
It has been pointed out recently that current experiments still allow for a two Higgs doublet model where the $h b \bar{b}$ coupling ($k_D m_b/v$) is negative; a sign opposite to that of the Standard Model. Due to the importance of delayed decoupling in the $h H^+ H^-$ coupling, $h \rightarrow γγ$ improved measurements will have a strong impact on this issue. For the same reason, measurements or even bounds on $h \rightarrow Z γ$ are potentially interesting. In this article, we revisit this problem, highlighting the crucial importance of $h \rightarrow VV$, which can be understood with simple …
In this paper we investigate CP violation in charged decays of $D$ meson. Particularly, we study the direct CP asymmetry of the Cabibbo favored non-leptonic $D^+ \rightarrow \bar K^0 π^+$ and the doubly Cabibbo-suppressed decay mode $D^+ \rightarrow K^0 π^+$ within standard model, two Higgs doublet model with generic Yukawa structure and left right symmetric models. In the standard model, we first derive the contributions from box and di-penguin diagrams contributing to their amplitudes which are relevant to the generation of the weak phases essential for non-vanishing direct CP violation. The…
In this work we consider a model for particle dark matter where an extra inert Higgs doublet and an additional scalar singlet is added to the Standard Model (SM) Lagrangian. The dark matter candidate is obtained from only the inert doublet. The stability of this one component dark matter is ensured by imposing a $Z_2$ symmetry on this additional inert doublet. The additional singlet scalar has a vacuum expectation value (VEV) and mixes with the Standard Model Higgs doublet resulting in two CP even scalars $h_1$ and $h_2$. We treat one of these scalars, $h_1$, to be consistent with the SM Higgs…
We investigate the lepton flavor violation (LFV) in the inert scalar model with higher representations. We generalize the inert doublet model with right handed neutrino by using higher scalar and fermion representation of $SU(2)_{L}$. As the generalized model and the inert doublet model have the same parameter space, we compare the rates of $μ\rightarrow eγ$, $μ\rightarrow ee\overline{e}$ and $μ-e$ conversion in nuclei in the doublet and its immediate extension, the quartet model. We show that the corresponding rates are larger in the case of higher representation compared to the Inert doublet…
The apparent excess of $Z \rightarrow b \bar b$ events at LEP may be an indication of new physics beyond the standard model. However, in either the two-Higgs-doublet model or the minimal supersymmetric standard model, any explanation would lead to an important new decay mode of the top quark and suppresses the $t \rightarrow W b$ branching fraction, which goes against what has been observed at the Tevatron. In the two-Higgs-doublet model, the branching fraction of $Z \rightarrow b \bar b$ + a light boson which decays predominantly into $b \bar b$ would be at least of order 10$^{-4}$.
There is no tree-level flavor changing neutral current (FCNC) in the standard model (SM) which contains only one Higgs doublet. If more Higgs doublets are introduced for various reasons, the tree level FCNC would be inevitable except extra symmetry was imposed. Therefore FCNC processes are the excellent probes for the physics beyond the SM (BSM). In this paper, we studied the lepton flavor violated (LFV) decay processes $h\rightarrowμτ$ and $τ\rightarrowμγ$ induced by Higgs-$μ$-$τ$ vertex. For $τ\rightarrowμγ$, its branching ratio is also related to the $ht\bar{t}$, $hτ^+τ^-$ and $hW^+W^-$ ver…
