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 $ξ$-independent of the result is also discussed. We find that numerical results are good stability with varying $ξ=0,1$ and $ξ\rightarrow \infty$.
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 \…
In this paper, new analytic formulas for one-loop contributing to Higgs decay channel $H \rightarrow Zγ$ are presented in terms of hypergeometric functions. The calculations are performed by following the technique for tensor one-loop reduction developed in [A.~I.~Davydychev, Phys.\ Lett.\ B {\bf 263} (1991) 107]. For the first time, one-loop form factors for the decay process are shown which are valid at arbitrary space-time dimension $d$.
One-loop on-shell and off-shell decays $H\rightarrow VV$ with $VV=γγ, Zγ, ZZ$ are presented in this paper. The effects of one-loop on-shell and off-shell Higgs decays in Higgs productions at $e^-e^-$ collisions are also then examined. We find that the impacts of one-loop Higgs decays are significant and they are must be taken into account at $e^-e^-$ collision.
The rare decays $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ are important to research new physics beyond standard model. In this work, we investigate two loop electroweak corrections to $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM), under a minimal flavor violating assumption for the soft breaking terms. In this framework, new particles and new definition of squarks can affect the theoretical predictions of these two processes, with respect to the MSSM. Considering the constraints fro…
It is emphasized that a rare decay $K^+ \rightarrow π^+ ν\barν$ becomes promising in a future search for a new particle, because the theoretical treatment is well established and the value of the branching ratio $Br(K^+ \rightarrow π^+ ν\barν)$ is sensitive to a search for a new particle with a TeV scale mass. As an example, according to a U(3) family gauge boson model which predicts the lowest family gauge boson with a few TeV mass $M_{11}$, the branching ratio $Br(K^+ \rightarrow π^+ ν\barν)$ is discussed. If we can obtain, in future, a slightly lower value $Br^{obs} \sim 0.9 \times 10^{-10}…
We present the two-loop master integrals relevant to the ${\mathcal O}(αα_s)$-corrections to the decay $H \rightarrow b \bar{b}$ through a $H t \bar{t}$-coupling. We keep the full dependence on the heavy particle masses, but neglect the $b$-quark mass. The occurring square roots can be rationalised and the result is expressed in terms of multiple polylogarithms.
Radiative corrections to the $h\rightarrow Zγ$ are evaluated in the one-loop approximation. The unitary gauge gauge is used. The analytic result is expressed in terms of the Passarino-Veltman functions. The calculations are applicable for the Standard Model as well for a wide class of its gauge extensions. In particular, the decay width of a charged Higgs boson $H^\pm \rightarrow W^\pmγ$ can be derived. The consistence of our formulas and several specific earlier results is shown.
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 …
We calculate one loop contributions to $Γ(h \rightarrow γ\, γ)$ from higher dimensional operators, in the Standard Model Effective Field Theory (SMEFT). Some technical challenges related to determining Electroweak one loop "finite terms" are discussed and overcome. Although we restrict our attention to $Γ(h \rightarrow γ\, γ)$, several developments we report have broad implications. Firstly, the running of the vacuum expectation value modifies the $\log(μ)$ dependence of processes in a manner that is not captured in some past SMEFT Renormalization Group (RG) calculations. Secondly, higher dime…
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…
Considering the constraints of the lepton flavor violating (LFV) processes $μ\rightarrow 3e$ and $τ\rightarrow3μ$ on the LFV couplings $Z'\ell_{i}\ell_{j}$, in the contexts of the $E_{6}$ models, the left-right (LR) models, the "alternative" left-right (ALR) models and the 331 models, we investigate the contributions of the extra gauge boson $Z'$ to the decay rates of the processes $\ell_{i}\rightarrow\ell_{j}ν_{\ell}ν_{\ell}$, $τ\rightarrowμP $ and $P\rightarrow μe$ with $P=π^{0},η$ and $η'$. Our numerical results show that the maximal values of the branching ratios for these processes are no…
We analyze the one loop correction to $Z\rightarrow νν$ decay in framework of Minimal R-symmetric Supersymmetric Standard Model(MRSSM) in detail with normal and inverse neutrino mass orderings, as a function of $\tanβ$, Dirac mass parameters $M_D^W$ and $μ_u(μ_d)$, slepton mass $m_l$ that parameterize the mass matrices. The numerical results indicate that the branching ratio for $Z\rightarrow νν$ decay is compatible with the experimental measurement and the SM expectation at $2σ$ level. For inverse neutrino mass ordering, the prediction exceeds the SM expectation at $1σ$ level. The prediction …
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…
We discuss off-shell contributions in Higgs decays to heavy gauge bosons $H\rightarrow VV^{(*)}$ with $V\in\lbrace Z,W\rbrace$ for a standard model (SM) Higgs boson for both dominant production processes $e^+e^-\rightarrow ZH\rightarrow ZVV^{(*)}$ and $e^+e^-\rightarrow ν\barνH\rightarrow ν\barνVV^{(*)}$ at a (linear) $e^+e^-$ collider. Dependent on the centre-of-mass energy off-shell effects are sizable and important for the understanding of the electroweak symmetry breaking mechanism. Moreover we shortly investigate the effects of the signal-background interference in $H\rightarrow γγ$ decay…
In this work, the radiative corrections to the production of a light Higgs boson ($h^0$) with a pair of lightest neutralinos (${\tildeχ}_1^0$) in $e^+ e^-$ collisions within MSSM are presented, including the on-shell renormalization scheme in the loop calculations. We have studied the QED corrections as well as the weak corrections, where the contribution from both corrections is significant and needs to be taken into account in the future linear colliders experiments. The result includes the numerical calculations for two different SUSY scenarios---Higgsino and Gaugino scenarios--- for $e^+ e…
General one-loop contributions to the decay amplitudes $H\rightarrow ν_l\barν_lγ$ are presented, considering all possible contributions of additional heavy vector gauge bosons, fermions, and charged (and also neutral) scalar particles appearing in the loop diagrams. Moreover, the results can be applied directly when extra neutrinos (apart from three ones in standard model) are taken into account in final states. Analytic results are presented in terms of Passarino-Veltman scalar functions which can be evaluated numerically using {\tt LoopTools}. In the standard model framework, these analytica…
The $e^+e^- \rightarrow ZH$ process is the dominant process for the Higgs boson production at the future Higgs factory. In order to match the analysis on the Higgs properties with the highly precise experiment data, it will be crucial to include the theoretical prediction to the full next-to-next-to-leading order electroweak effect in the production rate $σ(e^+e^-\rightarrow ZH)$. In this inspiring work, we categorize the two-loop Feynman diagrams of the $\mathcal O(α^2)$ correction to $e^+e^- \rightarrow ZH$ into 6 categories according to the relevant topological structures. Although 25377 di…
In this paper, we present the calculations for $H\rightarrow f\bar{f}γ$ in the $U(1)_{B-L}$ extension for Standard Model. Analytic results for one-loop form factors in the decay process are expressed in terms of the scalar one-loop Passarino$-$Veltman functions in the conventions of {\tt LoopTools}. Therefore, the decay rates can be evaluated numerically by using this package. In phenomenological results, we show the differential decay rates with respect to invariant mass of fermion pair $m_{ff}$, new neutral gauge mass $M_{Z'}$ and the coupling $g'$ of $U(1)_{B-L}$ gauge group. We find that t…
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.
We present general one-loop contributions to the decay processes $H\rightarrow f\bar{f}γ$ including all possible the exchange of the additional heavy vector gauge bosons, heavy fermions, and charged (also neutral) scalar particles in the loop diagrams. As a result, the analytic results are valid in a wide class of beyond the standard models. Analytic formulas for the form factors are expressed in terms of Passarino-Veltman functions in the standard notations of {\tt LoopTools}. Hence, the decay rates can be computed numerically by using this package. The computations are then applied to the ca…
The Hidden Abelian Higgs Model (HAHM) is an extension of the Standard Model based on the gauge group $G =SU(3)_{C} \times SU(2)_{L} \times U(1)_{Y} \times U(1)_{X}$ i.e. an extra $U(1)_{X}$ gauge group in addition to the SM gauge groups.In HAHM, an Abelian Hidden sector is coupled to the SM, and the resulting new Higgs boson H and new neutral gauge boson $Z_{HAHM}$ fields are allowed to mix with the corresponding SM fields. In this work, we search for the new neutral gauge boson $Z_{HAHM}$ and new Higgs boson in the context of the Hidden Abelian Higgs Model (HAHM) through the decay process $pp…
In this paper, we explore the collider phenomenology of the charged Higgs boson in the context of a generic Beyond Standard Model scenario with extended gauge and scalar sectors. In such scenarios, the charged Higgs boson can decay via the $W^{'}Z/ WZ^{'}$ channels. We formulate a search strategy for the $H^{\pm}$ in the channel $σ(g b \rightarrow H^{\pm}t)\mathcal{BR}(H^{\pm} \rightarrow W' Z)$ considering the interesting cascade decay chain $H^{\pm} \rightarrow W^{'} Z \rightarrow W^{\pm} Z Z$. We find that the charged Higgs can be discovered in final states with multiple hard leptons and/ o…
One-loop contributions to the decay $H\rightarrow ν_l\barν_lγ$ with $l=e, μ, τ$ within standard model framework are revisited in this paper. We derive two representations for the form factors in this calculation. As a result, the computations are not only checked numerically by verifying the ultraviolet finiteness of the results but also confirming the ward identity of the amplitude. We find that the results are good stability with varying ultraviolet cutoff parameters as well as satisfy the ward identity. In phenomenological results, all the physical results are examined with the present inpu…
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 $ς_u$. …
We put forward the framework of simplified leptoquark models: simple extensions of the Standard Model that serve as benchmarks to test the interactions of leptons with new colored degrees of freedom considered, for instance, in leptoquark or grand unification models. As a first application of the scheme, we analyze the power of precision lepton observables by computing gauge invariant two-loop radiative corrections to the lepton-photon vertex, generated here by Yukawa interactions between the lepton and new colored degrees of freedom. The result, detailed in explicit expressions for the involv…
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…
Two-loop QCD corrections to $ H \rightarrow b + \bar{b} + g $ at higher powers in the dimensional regulator
School of Physical Sciences, National Institute of Science Education and Research（国家科学教育研究中心物理科学学院）；Homi Bhabha National Institute（霍米·巴巴国立大学）；Theoretical Physics Division, Physical Research Laboratory（物理研究实验室理论物理部）；Department of Physics, Indian Institute of Technology Guwahati（古瓦哈提印度理工学院物理系）；The Institute of Mathematical Sciences（数学科学研究所）
本文计算了维度正则化参数 $\epsilon$ 高次幂下希格斯玻色子衰变到底夸克对和胶子（$H \rightarrow b + \bar{b} + g$）的两圈无质量QCD修正，通过将振幅投影到适当的洛伦兹结构上，并给出了形状因子的数值行为，这些振幅是计算强子对撞中底夸克湮灭产生希格斯加喷注的三圈虚修正的必要输入。
By using the GRACE-Loop system, we calculate the full $\mathcal{O}(α)$ electroweak radiative corrections to the process $e^+e^- \rightarrow e^+e^- γ$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range f…
We have calculated the $W$-loop contribution to the amplitude of the decay $H\rightarrow Z+γ$ in two different methods: 1) in the $R_ξ$-gauge using dimensional regularization (DimReg), and 2) in the unitary gauge through the dispersion method. Using the dispersion method we have followed two approaches: i) without subtraction and ii) with subtraction, the subtraction constant being determined adopting the Goldstone boson equivalence theorem (GBET) at the limit $M_W\to 0$. The results of the calculations in $R_ξ$-gauge with DimReg and the dispersion method with the GBET completely coincide, whi…
The dark photon is a new gauge boson which arises from an extra U'(1) gauge symmetry. In this paper, a novel dark photon production mechanism based on MeV-scale $γ$-$γ$ collider is considered: $γγ\rightarrow γA'$. With the aid of PACKAGE-X, differential cross section of $γγ\rightarrow γA'$ is obtained, as a function of the kinetic mixing parameter $\varepsilon$ and dark photon mass $m_{A'}$. Taking the light-by-light scattering as background, the constraints on the dark photon parameter space for different time intervals in a MeV-scale $γ$-$γ$ collider are also given.
Most searches for top partners, $T$, are concerned with top partner pair production. However, as these bounds become increasingly stringent, the LHC energy will saturate and single top partner production will become more important. In this paper we study the novel signature of the top partner produced in association with the SM top, $pp\rightarrow T\overline{t}+t\overline{T}$, in a model where the Standard Model (SM) is extended by a vector-like $SU(2)_L$ singlet fermion top partner and a real, SM gauge singlet scalar, $S$. In this model, $pp\rightarrow T\overline{t}+t\overline{T}$ production …
The 1-loop effects of the MSSM at the ILC are investigated through numerical analysis. We studied the higgs production processes $e^-e^+\rightarrow Zh$ and $e^-e^+\rightarrow ν\barνh$ at the ILC. It is found that the magnitude of the MSSM contribution through the 1-loop effects is sizable enough to be detected. In the study, three sets of the MSSM parameters are proposed, which are consistent with the observed higgs mass, the muon $g$-$2$, the dark matter abundance and the decay branching ratios of $B$ mesons. In the $e^-e^+\rightarrow Zh$ process, the 1-loop effects of the MSSM are visible an…
