在Higgs三重态模型中，考虑中微子质量矩阵的关联，将μ子反常磁偶极矩和轻子味破坏过程的约束转化为v_Delta*m_H ~（++）的下界.阐明了模型中μ子反常磁偶极矩贡献的符号与实验测量值的差异。结果表明，μ到e γ，τ衰变（特别是τ到μ e e），μ 鎓的转换可以给出一个更严格的约束v_Delta*m_H++比从μ到μ的约束，这是天真地期望给最严格的一个。
英文摘要：
Constraints from the muon anomalous magnetic dipole moment and lepton flavor violating processes are translated into lower bounds on v_Delta*m_H++ in the Higgs Triplet Model by considering correlations through the neutrino mass matrix. The discrepancy of the sign of the contribution to the muon anomalous magnetic dipole moment between the measurement and the prediction in the model is clarified. It is shown that mu to e gamma, tau decays (especially, tau to mu e e), and the muonium conversion can give a more stringent bound on v_Delta*m_H++ than the bound from mu to eee which is expected naively to give the most stringent one.
Axion-Like Particles (ALPs) are pseudo Nambu-Goldstone bosons associated with spontaneously broken global $U(1)$ symmetries. Such particles can have lepton-flavor-violating (LFV) couplings to the SM charged leptons. LFV ALPs provide the possibility to address some of the SM long-lasting problems. We investigate the sensitivity of a future muon collider suggested by the Muon Accelerator Program (MAP) to the production of LFV ALPs in the ALP mass range $m_a\leq1$ MeV. ALPs are assumed to be produced through the LFV decay $τ\ra\ell a$ ($\ell=e,μ$) of one of the tau leptons produced in the muon-an…
Electron-muon conversion in nuclei and rare decays induced by LFV dark photon
Bogoliubov Laboratory of Theoretical Physics, JINR（鲍戈留博夫理论物理实验室，俄罗斯联合核子研究所）；Matrosov Institute for System Dynamics and Control Theory SB RAS（马特罗索夫系统动力学与控制理论研究所，俄罗斯科学院西伯利亚分院）；Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR) of ANID（智利国家研究与创新发展局高能前沿亚原子物理学千年研究所（SAPHIR））；Center for Theoretical and Experimental Particle Physics, Facultad de Ciencias Exactas, Universidad Andres Bello（安德烈斯贝洛大学精确科学学院理论与实验粒子物理中心）；Institut für Theoretische Physik, Universität Tübingen, Kepler Center for Astro and Particle Physics（蒂宾根大学理论物理研究所，开普勒天体与粒子物理中心）
We investigate lepton flavor violation (LFV) in the the singlet-triplet scotogenic model in which neutrinos acquire non-zero masses at the 1-loop level. In contrast to the most popular variant of this setup, the singlet scotogenic model, this version includes a triplet fermion as well as a triplet scalar, leading to a scenario with a richer dark matter phenomenology. Taking into account results from neutrino oscillation experiments, we explore some aspects of the LFV phenomenology of the model. In particular, we study the relative weight of the dipole operators with respect to other contributi…
Lepton-flavor violating decays of neutral Higgs to muon and tauon in supersymmetric economical 3-3-1 model
在超对称经济3 - 3 - 1（SUSYE331）模型中研究了Higgs粒子到μ子-τ子的轻子味破坏（LFV）衰变.在sleptons {mu，tau}中存在风味混合和大的v/v '值时，Br（H--> tau ^+ mu ^-）/Br（H--> tau ^+ tau ^-）的比率可以达到不可忽略的值O（10 ^{-3}），如在许多已知的SUSY模型中那样。我们预测，对于标准模型的希格斯玻色子，大型强子对撞机可能会检测到它衰变为μ子和τ子。我们还研究了左右LFV修正值之间的不对称性，证明了LFV效应主要由左FLV项控制，在小的数值极限下，左FLV项比右LFV项大O（10^3）倍。|μ_ρ|/m_SUSY。Higgs介导的影响的衰变τ-->亩的贡献进行了讨论。
Significant deviations from Standard Model (SM) predictions have been observed in $ b \to s μ^+ μ^-$ decays and in the muon $g-2$. Scalar leptoquark extensions of the SM are known to be able to address these anomalies, but generically give rise to lepton flavor violation (LFV) or even proton decay. We propose new muon flavored gauge symmetries as a guiding principle for leptoquark models that preserve the global symmetries of the SM and explain the non-observation of LFV. A minimal model is shown to easily accommodate the anomalies without encountering other experimental constraints. This talk…
Lepton-flavor violation and muon $(g-2)$ in the flavor-dependent $U(1)_F$ model
Hebei University（河北大学）；Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province（河北省量子场论高精度计算与应用重点实验室）；Research Center for Computational Physics of Hebei Province（河北省计算物理研究中心）
We consider a supersymmetric type-I seesaw framework with non-universal scalar masses at the GUT scale to explain the long-standing discrepancy of the anomalous magnetic moment of the muon. We find that it is difficult to accommodate the muon g-2 while keeping charged-lepton flavor violating processes under control for the conventional SO(10)-based relation between the up sector and neutrino sector. However, such tension can be relaxed by adding a Georgi-Jarlskog factor for the Yukawa matrices, which requires a non-trivial GUT-based model. In this model, we find that both observables are compa…
We analyse in detail the scalar triplet contribution to the low-energy lepton flavour violating (LFV) and lepton number violating (LNV) processes within a TeV-scale left-right symmetric framework. We show that in both type-I and type-II seesaw dominance for the light neutrino masses, the triplet of mass comparable to or smaller than the largest right-handed neutrino mass scale can give sizeable contribution to the LFV processes, except in the quasi-degenerate limit of light neutrino masses, where a suppression can occur due to cancellations. In particular, a moderate value of the heaviest neut…
Flavor violating processes in the lepton sector have highly suppressed branching ratios in the standard model mainly due to the tiny neutrino mass. This means that observing lepton flavor violation (LFV) in the next round of experiments would constitute a clear indication of physics beyond the standard model (BSM). We revisit a discussion of one possible way to search for LFV, muonium-antimuonium oscillations. This process violates muon lepton number by two units and could be sensitive to the types of BSM physics that are not probed by other types of LFV processes. Using techniques of effectiv…
We assess the status of past and future experiments on lepton flavor violating (LFV) muon and tau decays into a light, invisible, axion-like particle (ALP), $a$. We propose a new experimental setup for MEG II, the MEGII-fwd, with a forward calorimeter placed downstream from the muon stopping target. Searching for $μ\to e a$ decays MEGII-fwd is maximally sensitive to LFV ALPs, if these have nonzero couplings to right-handed leptons. The experimental set-up suppresses the (left-handed) Standard Model background in the forward direction by controlling the polarization purity of the muon beam. The…
In these proceedings, we present a study of a combined singlet--doublet fermion and triplet scalar model for dark matter (DM). Together, these models form a simple extension of the Standard Model (SM) that can account for DM and explain the existence of neutrino masses, which are generated radiatively. However, this also implies the existence of lepton flavour violating (LFV) processes. In addition, this particular model allows for gauge coupling unification. The new fields are odd under a new $\mathbb{Z}_2$ symmetry to stabilise the DM candidate. We analyse the DM, neutrino mass and LFV aspec…
The Standard Model predicts that the Higgs boson couples to the fermions in the mass eigenstates. We consider the effects of lepton flavor violating (LFV) $Z$ boson couplings in the case where the Higgs boson has flavor non-diagonal Yukawa interactions with the muon and the tau lepton generated from physics beyond the Standard Model. We list the formulae of the couplings of the effective interactions among the $τ$ lepton, the muon and the $Z$ boson. Using these formulae, we calculate the branching fractions of various leptonic and hadronic LFV $τ$ decays, and the LFV $Z$ boson decay: $Z\to τμ$…
We investigate the bounds on tau-mu lepton flavor violation (LFV). Our main focus is on the collider constrains on tau-mu LFV. We use the Type-III Two-Higgs-Doublet-Model (2HDM) as a set up for our study. While the LFV branching fraction of the 125 GeV is well constrained by current LHC searches, the heavier neutral states could have a large branching fraction to tau and muon. We estimate the LHC reach for the 13 TeV center of mass energy with 300 $\text{fb}^{-1}$ luminosity for a neutral boson decaying into a tau and a muon. We identify parts of the LFV parameter space where the searches for …
Neutrino masses, muon g-2, and lepton-flavour violation in the supersymmetric see-saw model
In the light of the recent muon (g_mu-2) result by the E821 experiment at the Brookhaven National Laboratory, we study the event rates of the charged lepton-flavour-violating (LFV) processes in the supersymmetric standard model (SUSY SM) with the heavy right-handed neutrinos (SUSY see-saw model). Since the left-handed sleptons get the LFV masses via the neutrino Yukawa interaction in this model, the event rate of mu->e gamma and the SUSY-SM correction to (g_mu-2)/2 (δa_mu^{SUSY}) are strongly correlated. When the left-handed sleptons have a LFV mass between the first and second generations ((m…
Taking into account the constraints on the lepton flavor violation (LFV) couplings of the Standard Model (SM) Higgs boson H with leptons from low energy experiments and the recent Compact Muon Solenoid experiment results, we investigate production of the SM Higgs boson associated with a lepton τvia e γcollision at the International Linear Collider (ILC) and Large Hadron Electron Collider experiments. The production cross sections are calculated and the LFV signals and the relevant SM backgrounds are examined. The LFV signals of the SM Higgs boson might be observed via e γcollision in future IL…
We investigate a model based on hidden $U(1)_X$ gauge symmetry in which neutrino mass is induced at one-loop level by effects of interactions among particles in hidden sector and the Standard Model leptons. Neutrino mass generation is also associated with $U(1)_X$ breaking scale which is taken to be low to suppress neutrino mass. Then we formulate neutrino mass matrix, lepton flavor violating processes and muon $g-2$ which are induced via interactions among Standard Model leptons and particles in $U(1)_X$ hidden sector that can be sizable in our scenario. Carrying our numerical analysis, we sh…
Inspired by the recent measurement of the $h \to μτ$ decays by the CMS collaboration at the LHC, we study the lepton flavour-violating (LFV) $B_s \to μτ$ decays in the general two Higgs doublet model. Those LFV interactions could accommodate the present deviation of the muon anomalous magnetic moment and also predict the LFV $τ$ decay processes such as $τ\to μμμ$ and $τ\to μγ$. We find that the $B_s \to μτ$ decay rates should be sizable with above experimental conditions in the framework of our model. These processes are expected to be observed at the colliders such as LHCb and Belle-II in the…
The discrepancy between the measured value and the Standard Model prediction for the muon anomalous magnetic moment is one of the important issues in the particle physics. In this paper, we consider a two Higgs doublet model (2HDM) where the extra Higgs doublet couples to muon and tau in lepton flavor violating (LFV) way and the one-loop correction involving the scalars largely contributes to the muon anomalous magnetic moment. The couplings should be sizable to explain the discrepancy, so that the extra Higgs bosons would dominantly decay into $μτ$ LFV modes, which makes the model testable at…
We discuss a model based on a hidden $U(1)_X$ gauge symmetry in which neutrino mass is induced at two-loop level by effects of interactions among particles in hidden sector and the Standard Model leptons. Since neutrino mass is suppressed by two-loop, its associate Yukawa couplings can be sizable and it would affect lepton flavor phenomenology. We analyze neutrino mass matrix, lepton flavor violating processes, electron/muon $g-2$ and dark matter annihilation cross section which are induced via interactions among Standard Model leptons and particles in $U(1)_X$ hidden sector, and their interac…
We consider supersymmetric (SUSY) models for the muon $g-2$ anomaly without flavor violating masses at the tree-level. The models can avoid LHC constraints and the vacuum stability constraint in the stau-Higgs potential. Although large flavor violating processes are not induced within the framework of minimal SUSY standard model, once we adopt a seesaw model, sizable lepton flavor violating (LFV) processes such as $μ\to e γ$ and $μ\to e$ conversion are induced. These LFV processes will be observed at future experiments such as MEG-II, COMET and Mu2e if right-handed neutrinos are heavier than $…
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 re-examine lepton flavor violation (LFV) in the Littlest Higgs model with T--parity (LHT) including the full T--odd (non-singlet) lepton and Goldstone sectors. The heavy leptons induce two independent sources of LFV associated with the couplings necessary to give masses to the T--odd mirror fermions and to their partners in right-handed $SO(5)$ multiplets, respectively. The latter, which have been neglected in the past, can be decoupled from gauge mediated processes but not from Higgs mediated ones and must therefore also be included in a general analysis of LFV in the LHT. We also further …
We study the search potential of heavy triplet leptons in Type III Seesaw mechanism at future high-energy and high-luminosity muon colliders. The impact of up-to-date neutrino oscillation results is taken into account on neutrino parameters and the consequent decay patterns of heavy leptons in Type III Seesaw. The three heavy leptons in the Casas-Ibarra parametrization with diagonal unity matrix are distinguishable in their decay modes. We consider the pair production of charged triplet leptons $E^+ E^-$ through both $μ^+μ^-$ annihilation and vector boson fusion (VBF) processes. The leading-or…
Flavor violating processes in the lepton sector have highly suppressed branching ratios in the standard model. Thus, observation of lepton flavor violation (LFV) constitutes a clear indication of physics beyond the standard model (BSM). We review new physics searches in the processes that violate the conservation of lepton (muon) flavor by two units with muonia and muonium--antimuonium oscillations.
