Muon Anomalous Magnetic Moment Research Articles

Lepton pair production in muon-nucleus scattering

The MUonE experiment aims at providing a novel determination of the leading hadronic contribution to the muon anomalous magnetic moment through the study of elastic muon-electron scattering. Since the initial-state electrons are bound in a low-Z atomic target, the interaction between the incoming muons and the nuclei is expected to be the main source of experimental background. In this article, we study the production of a real lepton pair from the muon-nucleus scattering, discussing its numerical impact in the MUonE kinematic configuration. The process is described as a scattering of a muon in an external Coulomb field with the addition of a form factor to describe the nuclear charge distribution. The calculation is implemented in the fully differential Monte Carlo event generator Mesmer, without introducing any approximation on the angular variables.

Singlet-doublet fermion Dark Matter with Dirac neutrino mass, (g − 2)μ and ∆Neff

We study the possibility of generating light Dirac neutrino mass via scotogenic mechanism where singlet-doublet fermion Dark Matter (DM) plays non-trivial role in generating one-loop neutrino mass, anomalous magnetic moment of muon: (g − 2)μ as well as additional relativistic degrees of freedom ∆Neff within reach of cosmic microwave background (CMB) experiments. We show that the Dirac nature of neutrinos can bring interesting correlations within the parameter space satisfying the (g − 2)μ, DM relic density and the effective relativistic degrees of freedom ∆Neff. While we stick to thermal singlet-doublet DM with promising detection prospects, both thermal and non-thermal origin of ∆Neff have been explored. In addition to detection prospects of the model at DM, (g − 2)μ and other particle physics experiments, it remains verifiable at future CMB experiments like CMB-S4 and SPT-3G.

Towards a Standard Model with six fermion generations and a new breaking scale?

We propose here an enhanced version of the Standard Model based on the same local gauge group SU(3) c ⨂ SU(2) L ⨂ U(1) Y that undergoes a spontaneous symmetry breaking up to SU(3) c ⨂ U(1) em . We prove that it can naturally predict: (i) the electric and weak charges’ quantization, (ii) the muon anomalous magnetic moment discrepancy Δa μ , along with (iii) a realistic Higgs spectrum, (iv) a viable neutrino phenomenology, and (v) FCNCs suppression. This promising outcome—without spoiling any of the experimentally validated predictions of the Standard Model—occurs by simply assuming there are six non-universal fermion generations and two distinct scalar doublets. The latter ones develop different breaking scales, the old Standard Model scale v ≃ 246 GeV and a higher scale V —most likely in 1–100 TeV region, to be tested at LHC.

Secluded scalar dark matter and the muon anomalous magnetic moment

Abstract We consider a dark matter model with a singlet scalar, $\chi$, as our dark matter (DM) candidate which is secluded from the Standard Model (SM) and annihilates to the singlet scalar, $\phi$, via a contact interaction. 
The singlet scalar, $\phi$, has a leptophilic interaction with the SM leptons 
and may decay leptonically at tree level, and decays into a pair of photons at loop level. 
The focus in this work is to consider DM masses below 10 GeV. 
It is found a viable secluded region in the parameter space after imposing the observed 
relic density. There is a one-loop interaction between scalar dark matter and the atomic electron in this model. We then apply the available direct detection bounds from Xenon10, Xenon1T, and DarkSide on the DM-electron elastic scattering cross section. While the model can explain the muon anomalous magnetic moment, we put bounds from current and future lepton collider experiments.

Hadronic Light-by-Light Corrections to the Muon Anomalous Magnetic Moment

We review the hadronic light-by-light (HLbL) contribution to the muon anomalous magnetic moment. Upcoming measurements will reduce the experimental uncertainty of this observable by a factor of four; therefore, the theoretical precision must improve accordingly to fully harness such an experimental breakthrough. With regards to the HLbL contribution, this implies a study of the high-energy intermediate states that are neglected in dispersive estimates. We focus on the maximally symmetric high-energy regime and in-quark loop approximation of perturbation theory, following the method of the OPE with background fields proposed by Bijnens et al. in 2019 and 2020. We confirm their results regarding the contributions to the muon g−2. For this, we use an alternative computational method based on a reduction in the full quark loop amplitude, instead of projecting on a supposedly complete system of tensor structures motivated by first principles. Concerning scalar coefficients, mass corrections have been obtained by hypergeometric representations of Mellin–Barnes integrals. By our technique, the completeness of such kinematic singularity/zero-free tensor decomposition of the HLbL amplitude is explicitly checked.

A closer look at the U(1)B−L explanation of the ATOMKI nuclear anomalies

We revisit the gauged U(1)B−L explanation of the ATOMKI nuclear anomalies, in which the new gauge boson is the hypothetical X(17) particle. It is known that the vanilla B − L scenario is unable to account for appropriate couplings, namely the suppression of the couplings of X(17) to neutrinos, which motivates adding vector-like leptons. The simplest case, in which the new fields have B − L charges equal to 1, is highly disfavoured since it requires large mixing with the Standard Model fields. One solution recently put forward is to consider large B − L charges to counterbalance small mixing. We show that, in this scenario, and after taking into account several phenomenological constraints, the dominant contribution to the muon anomalous magnetic moment (g − 2)μ is expected to be extremely large and with a negative sign, being thus excluded by experiment.

Muon [formula omitted], dark matter, and neutrino mass explanations in a modular [formula omitted] symmetry

We study a successful model to explain the muon anomalous magnetic moment originating from Yukawa-type interactions in a supersymmetric theory. Thanks to a modular A4 flavor symmetry, any lepton flavor violations that spoil the model are forbidden. We also investigate a predictive radiative seesaw model including a dark matter (DM) candidate. At first, we construct the minimum model to satisfy the neutrino oscillation data and obtain several predictions such as Dirac CP and Majorana phases, the neutrino masses through χ2 analysis. However, the minimum model would not provide our promising DM candidate. Thus, we minimally extend the model and find a good DM candidate. In the extended framework, we show the allowed regions to satisfy the muon anomalous magnetic moment and the observed relic density of dark matter in addition to predictions of the lepton sector.

Gauge coupling unification in a minimal non-supersymmetric E6 GUT

We consider a minimal renormalizable non-supersymmetric [Formula: see text] Grand Unified Theory using fundamental representation 27 for fermions and scalars. The scalar with adjoint representation 78 is also taken for direct breaking of [Formula: see text] to SM. The proposed model, guided by TeV-scale vector-like fermions and scalar leptoquark, offers successful gauge unification even in the absence of any intermediate symmetry. Embedded with threshold corrections, it is shown to be compatible with the present experimental limit on proton decay lifetime. The unique feature of the model shows that the GUT threshold corrections to the unification mass is controlled by superheavy gauge bosons only, thereby minimizing the uncertainty of the GUT predictions. The scalar leptoquark and vector-like fermions residing in 27 representation can explain flavor physics anomalies like [Formula: see text] as reported by the LHCb collaboration and the muon anomalous magnetic moment reported by the recent muon [Formula: see text] experiment at Fermilab. The model can also predict a sub-eV scale neutrino at one-loop level via exchange of W and Z gauge bosons through MRIS mechanism.

Implementation of the frozen-spin technique for the search for a muon electric dipole moment

Applying the frozen-spin technique in a compact 3 T solenoid will enable a search for the muon electric dipole moment (EDM) with unprecedented sensitivity, improving upon the current direct limit by approximately a factor of 1000. After injection of a selected muon, a pulsed magnetic field will reduce its longitudinal momentum sufficiently to be confined within a static weakly-focusing magnetic field and maintain a closed circular orbit. A precisely tuned radial electric field will cancel the spin precession induced by the muon's anomalous magnetic moment, a = (g - 2)/2, relative to the orientation of the momentum. In this configuration, the EDM becomes the only remaining inherent source of relative precession. Asymmetry in the direction and energy of positrons emitted from muon decay provides an experimental signature of such precession.In the first of two phases, 28 MeV/c muons from the πE1 beamline at PSI will be used to demonstrate the systems necessary for injecting and trapping muons, tuning fields to the frozen-spin condition and reconstructing positron trajectories. Designs for the coils producing the pulsed magnetic field and the electrodes applying the frozen-spin electric field are currently being evaluated with simulations and prototypes. These systems must be designed in parallel, especially due to the impact of eddy-currents induced in the electrodes by the pulsed magnetic field. The electrode design must minimise eddy-currents to preserve the field strength of the pulsed field responsible for muon trapping, while maintaining the electric field uniformity necessary to achieve the sensitivity goal. This article summarises some of the efforts underway to address these design challenges.

Demonstration of Three-dimensional Spiral Injection for the J-PARC Muon g – 2/EDM Experiment

In the J-PARC Muon g-2/EDM experiment, to measure muon anomalous magnetic moment (g-2) and electrical dipole moment (EDM), it is necessary to accumulate 300MeV/c muon beams with a 66 cm diameter region with a 3 T solenoid-type magnetic field. A new three-dimensional spiral injection scheme has been invented to achieve this target. Since this is the first instance to employ this injection scheme, a scale-down experiment with an electron beam of 297 keV/c and storage beam diameter of 24 cm is established at KEK. A simplified storage beam monitor using scintillating fiber has been designed and fabricated to measure the stored beam. The 100 ns width pulsed beam is injected and the signal maintains a few microseconds by the stored beam observed. According to this result, the beam storage is confirmed. The recent result implies that the stored beam deviated from the design orbit and caused betatron oscillations. To measure the beam deviation quantitatively and tune the beam, the storage monitor has been updated. The data from this stored beam monitor are the primary data for considering the conceptual design of the beam monitor for the muon g-2/EDM experiment. This poster will discuss the measurement of beam storage by three-dimensional spiral injection and beam tuning using a scintillating fiber monitor.

Explanations of the tentative new physics anomalies and dark matter in the Simple Extension of the Standard Model (SESM)

We revisit the Simple Extension of the Standard Model (SESM), which can account for various tentative new physics anomalies and dark matter. The B physics anomalies, muon anomalous magnetic moment, and dark matter can be explained already in SESM. In this work, we study the unitarity constraint on this model and comment the parameter space on the edge of unitarity bounds. Besides, the complete scalar potential is considered which is needed to address the W boson anomaly and more dark matter (co-)annihilation processes are discussed. We perform a systematic study, and find the viable parameter space which can explain these anomalies and evade all the current experimental constraints.

Data-Driven Determination of the Light-Quark Connected Component of the Intermediate-Window Contribution to the Muon g-2.

We present the first data-driven result for a_{μ}^{win,lqc}, the isospin-limit light-quark connected component of the intermediate-window Hadronic-vacuum-polarization contribution to the muon anomalous magnetic moment. Our result, (198.8±1.1)×10^{-10}, is in significant tension with eight recent mutually compatible high-precision lattice-QCD determinations, and provides enhanced evidence for a puzzling discrepancy between lattice and data-driven determinations of the intermediate-window quantity, one driven largely by a difference in the light-quark connected component.

Fermion mass hierarchy in an extended left-right symmetric model

We present a Left-Right symmetric model that provides an explanation for the mass hierarchy of the charged fermions within the framework of the Standard Model. This explanation is achieved through the utilization of both tree-level and radiative seesaw mechanisms. In this model, the tiny masses of the light active neutrinos are generated via a three-loop radiative inverse seesaw mechanism, with Dirac and Majorana submatrices arising at one-loop level. To the best of our knowledge, this is the first example of the inverse seesaw mechanism being implemented with both submatrices generated at one- loop level. The model contains a global U(1)X symmetry which, after its spontaneous breaking, allows for the stabilization of the Dark Matter (DM) candidates. We show that the electroweak precision observables, the electron and muon anomalous magnetic moments as well as the Charged Lepton Flavor Violating decays, μ → eγ, are consistent with the current experimental limits. In addition, we analyze the implications of the model for the 95 GeV diphoton excess recently reported by the CMS collaboration and demonstrate that such anomaly could be easily accommodated. Finally, we discuss qualitative aspects of DM in the considered model.

Effects of the quark flavour thresholds in the hadronic vacuum polarization contributions to the muon anomalous magnetic moment

The equivalent representations for the hadronic vacuum polarization contributions to the muon anomalous magnetic moment in the presence of the quark flavour thresholds are studied. Specifically, the explicit relations between the contributions given by the integration over a finite kinematic interval to expressed in terms of the hadronic vacuum polarization function, Adler function, and the R-ratio of electron–positron annihilation into hadrons are derived. It is shown that the quark flavour thresholds of the hadronic vacuum polarization function generate additional contributions to expressed in terms of the Adler function and the R-ratio and the explicit expressions for such contributions are obtained. The commonly employed dispersion relations, which bind together hadronic vacuum polarization function, Adler function, and R-ratio, are extended to account for the effects due to the quark flavour thresholds. The examined additional contributions due to the heavy quark thresholds to expressed in terms of the R-ratio appear to be quite sizable, that can be of a particular relevance for the data-driven method of assessment of the hadronic part of the muon anomalous magnetic moment.

Study on muon MDM and lepton EDM in BLMSSM via the mass insertion approximation

In the framework of the MSSM extension with local gauged baryon and lepton numbers (BLMSSM), we calculate the muon anomalous magnetic dipole moment (MDM) and lepton (e, μ, τ) electric dipole moment (EDM), and discuss how the muon MDM and lepton EDM depend on the parameters within the mass insertion approximation. Among many parameters, , g L , m L and μ H are more sensitive parameters for . Considering the experimental limitations, our best numerical result of is around 2.5 × 10−9, which can well compensate the departure between the experiment data and standard model (SM) prediction. The CP violating phases in BLMSSM are more than those in the MSSM, including new parameters and θ L . They can give large contributions, which play an important role in exploring the source of CP violation and probing new physics beyond SM.

Phenomenology of dark tensor currents

In this work we suggest a dark mediator model which extends the usual U(1) Lagrangian by including new degrees of freedom coupling to Standard Model fermions. Such dark particles can contribute to the neutral pion decay. For interaction constant and the dark particle mass consistent with the observed anomalies in the nuclear decays by the ATOMKI group we show that the dark tensor particles naturally incorporate lepton universality violation which introduces sizable effect on the muon anomalous magnetic moment.

The O(αt+αλ+ακ)2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal{O}(\\alpha _t+\\alpha _\\lambda +\\alpha _\\kappa )^2$$\\end{document} correction to the ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document} parameter and its effect on the W boson mass calculation in the complex NMSSM

We present the prediction of the electroweak ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document} parameter and the W boson mass in the CP-violating Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM) at the two-loop order. The ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\rho $$\\end{document} parameter is calculated at the full one-loop and leading and sub-leading two-loop order O(α+αtαs+αt+αλ+ακ2)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {O}}(\\alpha + \\alpha _t\\alpha _s + \\left( \\alpha _t+\\alpha _\\lambda +\\alpha _\\kappa \\right) ^2)$$\\end{document}. The new Δρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\rho $$\\end{document} prediction is incorporated into a prediction of MW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_W$$\\end{document} via a full supersymmetric (SUSY) one-loop calculation of Δr\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta r$$\\end{document}. Furthermore, we include all known state-of-the-art SM higher-order corrections to Δr\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta r$$\\end{document}. By comparing results for Δρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\rho $$\\end{document} obtained using on-shell (OS) and DR¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{\ ext {DR}}$$\\end{document} renormalization conditions in the top/stop sector, we find that the scheme uncertainty is reduced at one-loop order by 55%, at two-loop O(αsαt)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {O}}(\\alpha _s\\alpha _t)$$\\end{document} by 22%, and at two-loop O(αt+ακ+αλ)2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathcal {O}}(\\alpha _t+\\alpha _\\kappa +\\alpha _\\lambda )^2$$\\end{document} by 16%, respectively. The influence of the two-loop results on the MW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_W$$\\end{document} mass prediction is found to be sub-leading. The new calculation is made public in the computer program NMSSMCALC. We perform an extensive comparison in the W-mass, Higgs boson mass and the muon anomalous magnetic moment prediction between our calculation and three other publicly available tools and find very good agreement provided that the input parameters and renormalization scales are treated in the same way. Finally, we study the impact of the CP-violating phases on the W-mass prediction which is found to be smaller than the overall size of the SUSY corrections.

New dark matter candidate in the B-L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B-L$$\\end{document} symmetric SSM

The B-L symmetric SUSY model (B-LSSM) introduces a new Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z'$$\\end{document} gauge boson and two singlet scalars, which indicates there are more neutralinos in the B-LSSM comparing with the minimal SUSY extension of standard model (MSSM). These new neutralinos provide more dark matter (DM) candidates in the B-LSSM, we find that the super partner of the new scalar singlet can serve as the lightest supersymmetric particle (LSP) and be considered as a DM candidate. The properties of this new DM candidate are analyzed in this work. Taking into account the experimental constraints on Higgs boson mass, B meson rare decays and muon anomalous magnetic dipole moment, the numerical results are obtained and presented. The properties of new DM candidate in the B-LSSM satisfy the observed relic density Ωh2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega h^2$$\\end{document} and comply with the latest upper bounds on σSIχ10-n\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma _\ extrm{SI}^{\\chi _1^0-n}$$\\end{document}, and its mass is expected to greater than 80GeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$80\\;\ extrm{GeV}$$\\end{document} approximately.

A model with vectorlike fermions and U(1)X symmetry: CKM unitarity, b → s transitions, and prospect at Belle II

The updated analysis of the LHCb Collaboration on the lepton flavor violation suggests that the new physics should couple to muons and electrons with comparable magnitudes, resulting in the anomalies in both rare decay channels, b→sμ+μ− and b→se+e−. Meanwhile, the recent result of the Muon g−2 experiment with higher precision has increased the existing tension with the standard model prediction. In this paper, we consider an extension of the standard model with a new sector consisting of vectorlike fermions and two scalar charged under an extra U(1)X gauge symmetry. The exotic Yukawa interactions in this model lead to the quark mixing responsible for the additional contributions to the flavor changing neutral currents in B-meson decays, and solve the muon g−2 discrepancy. We derive the analytic expression of the new physics contributions to the Wilson coefficient C7 in the effective Hamiltonian, and point out that the CKM unitarity violation can be explained within this context. By calculating the branching ratio of the inclusive radiative B decay, the impact of current experimental data of the b→sγ transition on the model and the future prospect at the Belle II experiment are investigated. Taking into account the current data on the muon anomalous magnetic moment, the CKM unitarity violation, the constraints on the flavor observables relevant to the b→s transitions, the LHC searches for vectorlike quarks, and the perturbation limits of the couplings, the viable parameter regions of the model are identified.

Stability of electroweak vacuum and supersymmetric contribution to muon g − 2

We study the stability of the electroweak vacuum in the supersymmetric (SUSY) standard model (SM), paying particular attention to its relation to the SUSY contribution to the muon anomalous magnetic moment aμ. If the SUSY contribution to aμ is sizable, the electroweak vacuum may become unstable because of enhanced trilinear scalar interactions. With aμ being fixed, larger slepton masses require more enhanced trilinear couplings, which make the electroweak vacuum more unstable. Thus, assuming SUSY contribution to aμ being sizable, an upper bound on the slepton masses is obtained. We give a detailed prescription to perform a full one-loop calculation of the decay rate of the electroweak vacuum for the case that the SUSY contribution to aμ is enhanced. We also give an upper bound on the slepton masses as a function of the SUSY contribution to aμ.