One-loop $W$ boson contributions to the decay $H\rightarrow Zγ$ in the general $R_ξ$ gauge are presented. The analytical results are expressed in terms of well-known Passarino-Veltman functions which their numerical evaluations can be generated using {\tt LoopTools}. In the limit $d\rightarrow 4$, we have shown that these analytical results are independent of the unphysical parameter $ξ$ and consistent with previous results. The gauge parameter independence are also checked numerically for consistence. Our results are also well stable with different values of $ξ=0, 1, 100,$ and $ξ\rightarrow \infty$.
To gain some sense about the likelihood of measuring the Higgs boson quartic coupling, we calculate the contribution to the triple Higgs production cross section from the subprocesses $q\bar{q}\to ZHHH$ and $q\bar{q}'\to WHHH$. Our results illustrate that determining this coupling, or even providing experimental evidence that it exists, will be very difficult.
$U(1)_X$SSM is the extension of the minimal supersymmetric standard model (MSSM) and its local gauge group is $SU(3)_C\times SU(2)_L \times U(1)_Y \times U(1)_X$. We study lepton flavor violating (LFV) decays $Z\rightarrow{{l_i}^{\pm}{l_j}^{\mp}}$($Z\rightarrow eμ$, $Z\rightarrow eτ$, and $Z\rightarrow μτ$) and $h\rightarrow{{l_i}^{\pm}{l_j}^{\mp}}$($h\rightarrow eμ$, $h\rightarrow eτ$, and $h\rightarrow μτ$), in this model. In the numerical results, the branching ratios of $Z\rightarrow{{l_i}^{\pm}{l_j}^{\mp}}$ are from $10^{-9}$ to $10^{-13}$ and the branching ratios of $h\rightarrow{{l_i}^{…
Recently, the ATLAS and CMS Collaborations reported the latest experimental upper limits on the branching ratios of the lepton flavor violating (LFV) 125 GeV Higgs boson decays, $h\rightarrow eμ$, $h\rightarrow eτ$, and $h\rightarrow μτ$. In this paper, we mainly investigate the LFV Higgs boson decays $h\rightarrow eμ$, $h\rightarrow eτ$, and $h\rightarrow μτ$ in the minimal supersymmetric extension of the Standard Model with local $\emph{B-L}$ gauge symmetry. At the same time, the corresponding constraints from the LFV rare decays $μ\rightarrow eγ$, $τ\rightarrow eγ$, $τ\rightarrow μγ$, and m…
We compute the contributions to rare top decays $t\rightarrow cZ$ and $t\rightarrow ch_1$ from the scalar sector in the 2HDM type III with CP violation, where $h_1$ is the Standard Model Higgs boson. The branching ratio for $BR(t\rightarrow c Z)$ and $BR(t\rightarrow c h_1)$ are obtained as a function of the model parameters. In particular, the $BR(t\rightarrow c Z)$ can increase its value up to $10^{-3}$ for $\tanβ= 1$ and masses for the additional Higgs bosons of $m_{h_2,h_3,H^\pm}\sim 0.5$ TeV. Meanwhile $BR(t\rightarrow c h_1)$ can reach values of the order of $\sim10^{-2}$. We constrain t…
In the framework of the flipped 3-3-1 model introduced recently [1], the lepton-flavor-violating (LFV) decay $μ\rightarrow 3e$ was predicted to have a large branching ratio (Br) close to the recent experimental limit. We will show that the Br of LFV decays of the standard-model-like (SM-like) Higgs boson decays (LFVHD) Br$(h\rightarrow e_ae_b)$ may also be large. Namely, the Br$(h\rightarrow μτ,eτ)$ can reach values of $\mathcal{O}(10^{-4})-\mathcal{O}(10^{-5})$, which will reach the upcoming experimental sensitivities. On the other hand, for LFV decays of charged leptons (cLFV) $(e_b\rightarr…
In this study, we investigate the light charged Higgs boson production via $pp \rightarrow H^\pm bj$ in the type-I configuration of the Two-Higgs Doublet Model (2HDM). In the viable parameter space, assuming either $h$ or $H$ is the SM-like Higgs boson observed at the Large Hadron Collider (LHC), we focus on the bosonic decays $H^\pm \rightarrow W^\pm A/h$ and examine the final states arising from the above charged Higgs production and decay. We show here that the suggested signatures can have sizable rates, reaching the pb level, when the top quark is produced on-shell and $\tanβ$ is small.
We present a detailed analysis of the Higgs boson decays $h\rightarrow Z γ$ and $h\rightarrow m_V Z$ in the $U(1)_X$SSM, with $m_V$ denoting the meson ($ω,ρ,ϕ,J/ψ,Υ$). Using the effective Lagrangian method, we calculate the effective constants $C_{γZ}$ (CP-even) and $\tilde{C}_{γZ}$ (CP-odd) for the vertex $h γZ$, which are corrected by the new particle loop diagrams. Numerically, the ratio $Γ_{U(1)_X}(h\rightarrow Z γ)/Γ_{SM}(h\rightarrow Z γ)$ is between $1.02-1.35$. For the vector mesons $ω,ρ,ϕ$ and $J/ψ$, the ratios $Γ_{U(1)_X}(h\rightarrow m_V Z )/Γ_{SM}(h\rightarrow m_V Z)$ are mainly di…
Weak vector boson scattering (VBS) at the LHC provides an excellent source of information on the structure of quartic gauge couplings and possible effects of physics beyond the SM in electroweak symmetry breaking. Parameterizing deviations from the SM within an effective field theory at tree level, the dimension-8 operators, which are needed for sufficiently general modeling, lead to unphysical enhancements of cross sections within the accessible energy range of the LHC. Preservation of unitarity limits is needed for phenomenological studies of the $VVjj$ events which signify VBS. Here we deve…
Investigation of CP-even Higgs bosons decays $H \rightarrow μτ$ within constraints of $l_a \rightarrow l_b γ$ in a 3-3-1 model with inverse seesaw neutrinos
Polarization effects in electroweak vector boson productions
考虑了矢量玻色子$e^+ e^- \rightarrow Z γ$、$γe \rightarrow Ze$和$γe \rightarrow W ν$的电弱产生过程，并在标准模型中由其中一个过程$γe \rightarrow Z e$得到了这些过程的协变极化密度矩阵.考虑了光子极化和矢量介子极化的影响，并讨论了一些特殊情况。
Consideration of the latest experimental data on the searches for extended sector of Higgs bosons produced at the LHC at a center-of-mass energy of 13 TeV, allows for computer modeling of the properties of supersymmetric particles within 2HDM model. The experimental restrictions on model parameters accounted in FeynHiggs code that is implemented in SusHi program, gave us the possibility to calculate the cross sections and branching fractions for three mechanisms of production and decay of Higgs bosons: 1) pp$\rightarrow H\rightarrowττ$, 2) pp$\rightarrow A\rightarrow Zh\rightarrow llbb$, 3) pp…
Neutral gauge bosons beyond the Standard Model are becoming interesting as possible mediators to explain several experimental anomalies. They have small masses, below one GeV, and are referred to as dark photons, $U$, $A'$ or $Z'$ bosons. Electron--positron collision experiments at the B-factories provide the most straightforward way to probe bosons of this kind. In the present article we study production of the bosons at $e^+e^-$ colliders operating at GeV center-of-mass energies. We have studied two channels: $e^+e^-\rightarrow γZ'$ and $e^+e^-\rightarrow e^+e^-Z'$. Analytic expressions for …
We discuss a list of possible light gauge boson interpretations for the long-standing experimental anomaly in $(g-2)_μ$ and also recent anomalous excess in $K_L \rightarrow π^0 + \text{(invisible)}$ events at the J-PARC KOTO experiment. We consider two models: $i$) $L_μ- L_τ$ gauge boson with heavy vector-like quarks and $ii$) $(L_μ- L_τ) + ε(B_3 - L_τ)$ gauge boson in the presence of right-handed neutrinos. When the light gauge boson has mass close to the neutral pion in order to satisfy the Grossman-Nir bound, the models successfully explain the anomalies simultaneously while satisfying all …
The $2\rightarrow 3$ scattering of longitudinal vector bosons (VBS) has been proven to be a complementary channel to measure the Higgs self-couplings in the Standard Model (SM) and the SM effective field theory (SMEFT) at colliders. We perform the first comprehensive study of all main $2\rightarrow 3$ VBS processes at high-energy muon colliders, especially including background analysis. The main contributing channels turn out to be the scattering of $W^+W^-\rightarrow W^+W^-h$, $ZZh$ and $hhh$. We obtain the constraints on $c_6$ and $c_{Φ_1}$ which are the Wilson coefficients of the dimension-…
In the framework of BLMSSM, the Higgs decays $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$ are studied where $m_V$ represents a vector meson($ρ, ω, ϕ, J/ψ, Υ$ etc.). Corrections to the CP-even and CP-odd $h^0γZ$ couplings occur via loop diagrams where new particles are involved. Actually both of them obviously influence the decay rates of $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$. Concretely, our obtained numerical result shows that the decay width of $h^0\rightarrow Zγ$ can be 1.3 times larger than the prediction of the Standard Model(SM). For the light mesons ($ρ,ω$), the corrections to …
To solve the $μ$ problem and generate three tiny neutrino masses in the MSSM, the $μ$ from $ν$ Supersymmetric Standard Model ($μν$SSM) introduces three singlet right-handed neutrino superfields, which lead to the mixing of the Higgs doublets with the sneutrinos. The mixing affects the lightest Higgs boson mass and the Higgs couplings. The present observed 95\% CL upper limit on signal strength of the 125 GeV Higgs boson decay $h\rightarrow Zγ$ is 6.6, which still is plenty of space to prove the existence of new physics. In this work, we investigate the signal strength of the 125 GeV Higgs boso…
In the framework of the minimal $U(1)_{B-L}$ extension of the Standard Model, we investigate the Higgs boson production processes $e^{+}e^{-}\rightarrow ZH$, $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}H$, $e^{+}e^{-}\rightarrow t\bar{t}H$, $e^{+}e^{-}\rightarrow ZHH$ and $e^{+}e^{-}\rightarrow ν_{e}\bar{ν_{e}}HH$ at the International Linear Collider (ILC). We present the production cross sections, the relative corrections and compare our results with the expected experimental accuracies for Higgs decay channel $H\rightarrow b\bar{b}$. In the allowed parameter space, we find that the effects of the…
The phenomenological implications to the decay of the neutral pion from the introduction of new dark particles are discussed. We calculate the contribution to the $π^0$ decay width and then we extend the theory by adding dark sector vector particles which interact through $γ^μ$, $σ^{μν}$ and $σ^{μν}γ^5$. We calculate the total decay width of $π^0\rightarrow γe^+ e^-$ where the electron-positron pair is produced through a decay of a dark meson. The implication of the presented model on the present and future searches for new dark particles is also discussed.
We analyze the flavor violating muon decay $μ\rightarrow eχ$, where $χ$ is a massive gauge boson, with emphasis in the regime where $χ$ is ultralight. We first study this process from an effective field theory standpoint in terms of form factors. We then present two explicit models where $μ\rightarrow eχ$ is generated at tree level and at the one-loop level. We also comment on the prospects of observing the process $μ\rightarrow eχ$ in view of the current limits on $μ\rightarrow 3e$ from the SINDRUM collaboration.
By adding new gauge singlets of neutral leptons, the improved versions of the 3-3-1 models with right-handed neutrinos have been recently introduced in order to explain recent experimental neutrino oscillation data through the inverse seesaw mechanism. We prove that these models predict promising signals of lepton-flavor-violating decays of the standard-model-like Higgs boson $h^0_1\rightarrow μτ,eτ$, which are suppressed in the original versions. One-loop contributions to these decay amplitudes are introduced in the unitary gauge. Based on a numerical investigation, we find that the branching…
Models with extended Higgs boson sectors are of prime importance for investigating the mechanism of electroweak symmetry breaking for Higgs decays into four fermions and for Higgs-production in association with a vector bosons. In the framework of the Two-Higgs-Doublet Model using two scenarios obtained from the experimental measurements we presented next-to-leading-order results on the four-fermion decays of light CP-even Higgs boson, $h \rightarrow 4f$. With the help of Monte Carlo program Prophecy 4f 3.0, we calculated the values $Γ= Γ_{EW} /\left(Γ_{EW}+Γ_{SM}\right)$ and $Γ= Γ_{EW+QCD} /\…
I present higher-order radiative corrections from collinear and soft gluon emission for the associated production of a charged Higgs boson with a $W$ boson. The calculation uses expressions from resummation at next-to-leading-logarithm accuracy. From the resummed cross section I derive analytical formulas at approximate NNLO and N$^3$LO. Total cross sections are presented for the process $b{\bar b} \rightarrow H^- W^+$ at various LHC energies. The transverse-momentum and rapidity distributions of the charged Higgs boson are also calculated.
We investigate the light charged Higgs boson production via $pp \rightarrow H^\pm h$ at the Large Hadron Collider (LHC) in the Two-Higgs Doublet Model (2HDM) type-I. By focusing on a scenario where $H$ is the observed Higgs boson of mass 125 GeV, we study the aforementioned Higgs boson production channel and explore its bosonic decay $H^\pm \rightarrow W^\pm h$. The latter can have a sizable rate that possibly dominates, over the fermionic decay channels, in several regions of the viable parameter space. We demonstrate that the production process $pp \rightarrow H^\pm h$ followed by $H^\pm \ri…
The present anomaly in muon anaomalous magnetic moment can be explained by the presence of a muon-philic $X$ boson which could be a scalar particle or a vector particle with mass less than twice the mass of muon. The muon-philic $X$ boson could interestingly not be a parity eigenstate as well. If there exists such a boson, irrespective of its parity, it can be directly observed in the decay $J/ψ\to μ^- μ^+ X$ where $X$ remains invisible. We show that by using the angular distribution or the distribution of events in the square Dalitz plot, along with two well defined dimensionless ratios, one …
We study the measurement of Higgs boson self-couplings through $2\rightarrow 3$ vector boson scattering (VBS) processes in the framework of Standard Model effective field theory (SMEFT) at both proton and lepton colliders. The SMEFT contribution to the amplitude of the $2\to3$ VBS processes, taking $W_L W_L\rightarrow W_L W_L h$ and $W_L W_L\rightarrow h h h$ as examples, exhibits enhancement with the energy $\frac{\mathcal{A}^{\text{BSM}}}{\mathcal{A}^{\text{SM}}} \sim \frac{E^2}{Λ^2}$, which indicates the sensitivity of these processes to the related dimension-six operators in SMEFT. Simulat…
A future $Z$-factory will offer the possibility to study rare $Z$ decays $Z\rightarrow l_1l_2$, as those leading to Lepton Flavor Violation final states. In this work, by taking account of the constraints from radiative two body decays $l_2\rightarrow l_1γ$, we investigate the Lepton Flavor Violation decays $Z\rightarrow l_1l_2$ in the framework of Minimal R-symmetric Supersymmetric Standard Model with two benchmark points from already existing literatures. The flavor violating off-diagonal entries $δ^{12}$, $δ^{13}$ and $δ^{23}$ are constrained by the current experimental bounds of $l_2\right…
In this paper, we present general one-loop form factors for $H\rightarrow γ^* γ^*$ in $R_ξ$ gauge, considering all cases of two on-shell, one on-shell and two off-shell for final photons. The calculations are performed in standard model and in arbitrary beyond the standard models which charged scalar particles may be exchanged in one-loop diagrams. Analytic results for the form factors are shown in general forms which are expressed in terms of the Passarino-Veltman functions. We also confirm the results in previous computations which are available for the case of two on-shell photons. The $ξ$-…
The searches for charged Higgs bosons can be used to probe new physics at the LHC. In the current study, we concentrate on the associated production of the charged Higgs boson with the bottom quark and the jet in Two-Higgs Doublet Model (2HDM) type-I as promising mode for a light $H^\pm$, i.e. $m_{H^\pm}<m_t$. For this we consider the two situations where $h$ or $H$ is the SM-type Higgs boson discovered with a mass close to 125 GeV and investigate its bosonic decays, namely $H^{\pm} \to W^{\pm} h$ and/or $H^{\pm} \to W^{\pm} A$. The potential signals at the LHC are then discussed, under both t…
The Elementary Goldstone Higgs (EGH) model is a perturbative extension of the standard model (SM), which identifies the EGH boson as the observed Higgs boson. In this paper, we study pair production of the EGH boson in future linear electron positron colliders. The cross sections in the TeV region can be changed to about $-27\%$, $163\%$ and $-34\%$ for the $e^+e^-\rightarrow Zhh$, $e^+e^-\rightarrow ν\barνhh$, and $e^+e^-\rightarrow t\bar{t}hh$ processes with respect to the SM predictions, respectively. According to the expected measurement precisions, such correction effects might be observe…
We review the role of the Higgs boson in preserving unitarity of the scattering amplitudes in the Standard Model (SM). We will look at the processes $ν_e + \barν_e \rightarrow W^-_L +W^+_L $, $ W^-_L + W^+_L \rightarrow W^-_L +W^+_L $ and $e^- + e^+ \rightarrow W^-_L +W^+_L $ for longitudinally polarized gauge bosons. Special emphasis will be put in using algebraic methods to evaluate the amplitudes and cross sections. This note is based on Lectures given at the IDPASC Schools in Udine (2012) and Braga (2014).
We investigate the potential of the Compact Linear Collider (CLIC) to probe the anomalous $W^+W^-γ$ coupling in $γγ$, $γγ^*$ and $γ^*γ^*$ collisions through the processes $γγ\rightarrow W^+ W^-$, $e^+ γ\rightarrow e^+ γ^{*} γ\rightarrow e^+ W^- W^+$ and $e^+ e^-\rightarrow e^+ γ^{*} γ^{*} e^- \rightarrow e^+ W^- W^+ e^-$. We perform leptonic, semi-leptonic and hadronic decays channels for $W^+W^-$ production in the final state. Taking ${\cal L}=1\hspace{0.8mm}{\rm ab^{-1}}@ \sqrt{s}=0.380\hspace{0.8mm}{\rm TeV}$, ${\cal L}=2.5\hspace{0.8mm}{\rm ab^{-1}}@ \sqrt{s}=1.5\hspace{0.8mm}{\rm TeV}$ an…
