Muon Anomalous Magnetic Moment in the Supersymmetric Models with and Without Right—Handed Neutrinos

We discuss the anomalous magnetic moment of muon in the minimal supersymmetric model with and without right-handed neutrinos. In the same framework, the decay width of is also evaluated. Considering the measured value of muon in the E821 experiment and other experimental constraints on the lepton-flavor-violation processes, we carry out numerical analysis on the concerned observables in the minimal supergravity scenario.

Magnetic correction to the anomalous magnetic moment of electrons

We investigate the leading order correction of anomalous magnetic moment(AMM) to electrons in a weak magnetic field and find that the magnetic correction is negative and magnetic field dependent, indicating a magnetic catalysis effect for the electron gas. In the laboratory, to measure the g-2, the magnitude of the magnetic field B is several T, and correspondingly the magnetic correction to the AMM of electron/muon is around 10^(-34)/10^(-42), therefore the magnetic correction can be safely neglected in the current measurement. However, when the magnitude of the magnetic field strength is comparable with the electron mass, the magnetic correction of the electron’s AMM will become considerable. This general magnetic correction to the charged fermion’s AMM can be extended to study quantum chromodynamic matter under a strong magnetic field.

Study of Ratio of Proton Momentum Distributions with a Chiral Quark Model

The ratio between the anomalous magnetic moments of proton and neutron has recently been suggested to be connected to the ratio of proton momentum fractions carried by the valence quarks inside it. This moment fraction ratio is respectively evaluated by using constituent quark model and chiral quark model in order to check meson cloud effect. Our results show that the meson cloud effect is remarkable to the ratio of the proton momentum fractions, and therefore, this ratiois a sensitive test for the meson cloud effect as well as for the SU(6) symmetry breaking effect.

Fine Structure Constant Model Demonstrates the Electron Elementary Charge of Having an Intrinsic Manifold

Using our recently published electron’s charge electromagnetic flux manifold fiber model of the electron, described by analytical method and numerical simulations, we show how the fine structure constant is embedded as a geometrical proportionality constant in three dimensional space of its charge manifold and how this dictates the first QED term one-loop contribution of its anomalous magnetic moment making for the first time a connection of its intrinsic characteristics with physical geometrical dimensions and therefore demonstrating that the physical electron charge cannot be dimensionless. We show that the fine structure constant (FSC) α, and anomalous magnetic moment αμ of the electron is related to the sphericity of its charge distribution which is not perfectly spherical and thus has a shape, and therefore its self-confined charge possesses measurable physical dimensions. We also explain why these are not yet able to be measured by past and current experiments and how possible we could succeed.

Muon g - 2 in the Littlest Higgs Model

In this paper the anomalous magnetic dipole moment ofmuon in the littlest Higgs （LH） model is studied at one-loop level. We discuss the dependence of the contributions on the global symmetry breaking scale f, mizing angles c` and , and the Higgs triplet vacuum expectation value v＇ in the electroweak precision data preferring ranges. We find that the LH model can give a relatively small, but non-negligible extra weak contribution to the muon anomalous magnetic moment and can reduce the deviation of △aμ from 2.6σ for the SM to 2.5σ for the LH model.

Two-Higgs-doublet models in light of current experiments:a brief review

We briefly survey several typical CP-conserving two-Higgs-doublet models(2HDMs)in light of current experiments.First we derive the masses and couplings of the mass eigenstates from the Lagrangians.Then we analyze the constraints from theory and oblique electroweak parameters.Finally,we delineate the status of 2HDM in light of the LHC searches,the dark matter detections and the muon g-2 measurement.

Hadronic light-by-light scattering contribution to the muon g-2

We review recent developments concerning the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. We first discuss why fully off-shell hadronic form factors should be used for the evaluation of this contribution to the g- 2. We then reevaluate the numerically dominant pion-exchange contribution in the framework of large-No QCD, using an off-shell pion-photon-photon form factor which fulfills all QCD short-distance constraints, in particular, a new short-distance constraint on the off-shell form factor at the external vertex in g- 2, which relates the form factor to the quark condensate magnetic susceptibility in QCD. Combined with available evaluations of the other contributions to hadronic light-by-light scattering this leads to the new result αμ^LbyL;had= （116±40） × 10^-11, with a conservative error estimate in view of the many still unsolved problems. Some potential ways for further improvements are briefly discussed as well. For the electron we obtain the new estimate αe^LbyL;had= （3.9± 1.3） × 10^-14.

Update of g-2 of the muon and △α

We update our Standard Model predictions for g-2 of the muon and for the hadronic contributions （5） 2 to the running of the QED coupling, Δαbad^5）（MZ^2）. Particular emphasis is put on recent changes in the hadronic contributions from new data in the 2π channel and from the energy region just below 2 GeV.

A multi-charged particle model with local U(1)_(μ-τ) to explain muon g-2,flavor physics,and possible collider signature

We consider a model with multi-charged particles,including vector-like fermions,and a charged scalar under a local U(1)_(μ−τ) symmetry.We search for an allowed parameter region explaining muon anomalous magnetic moment(muon g−2)and b→sℓ^(+)ℓ^(−) anomalies,satisfying constraints from the lepton flavor violations,Z boson decays,meson anti-meson mixing,and collider experiments.Via numerical analysis,we explore the typical size of the muon g−2 and Wilson coefficients to explain the b→sℓ^(+)ℓ^(−) anomalies in our model when all other experimental constraints are satisfied.Subsequently,we discuss the collider physics of the multicharged vectorlike fermions,considering a number of benchmark points in the allowed parameter space.

Impact of LHC probes of SUSY and recent measurement of(g-2)_μon Z_(3)-NMSSM

It is well known that excessively heavy supersymmetric particles(sparticles)are disfavored to explain the(g−2)_(μ) anomaly,but some people overlook that moderately light sparticles are also disfavored by the LHC probes of supersymmetry.We take the Next-to-Minimal Supersymmetric Standard Model as an example to emphasize the latter point.It is found that,if the theory is required to explain the anomaly at 2σlevel and meanwhile keep consistent with the LHC results,the following lower bounds may be set:tanβ&20,|M_(1)|&275 GeV,M_(2)&300 GeV,μ&460 GeV,m_(μL)&310 GeV,and m_(μR)&350 GeV,where M_(1)and M_(2)denote gaugino masses,μrepresents the Higgsino mass,and m_(μL)and m_(μR)are the mass of Smuons with L and R denot-ing their dominant chiral component.This observation has significant impacts on dark matter(DM)physics,e.g.,the popular Z-and Higgs-funnel regions have been excluded,and the Bino-dominated neutralino DM has to co-annihilate with the Wino-dominated electroweakinos(in most cases)and/or Smuons(in few cases)to obtain the correct density.It is also inferred that these conclusions keep valid for the Minimal Supersymmetric Standard Model since the underlying physics for the bounds are the same.

Joint explanation of W-mass and muon g-2 in the 2HDM

Because both W-mass and muon g-2 can be affected by mass splittings among extra Higgs bosons(H,A,H^(±))in a two-Higgs-doublet model,we take a model with μ-τ lepton flavor violation interactions to examine the two anomalies reported by CDFⅡ and FNAL.We obtain the following observations:(ⅰ)Combined with theoretical constraints,the CDF W-mass measurement disfavors H or A degenerating in mass with H^(±)but allows H and A to degenerate.The mass splitting between H^(±)and H/A must be larger than 10 GeV.m_(H) and m_(A) are favored to be smaller than 650 GeV for m_(H)<120 GeV and allowed to have larger values with increasing m_(H).(ⅱ)After imposing other relevant experimental constraints,there are parameter spaces that simultaneously satisfy(at the 2σ level)the CDF W-mass,FNAL muon g-2,and data on lepton universality in τ decays;however,the mass splittings among extra Higgs bosons are strictly constrained.

Status of the Fermilab muon (g-2) experiment

The New Muon （g-2） Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, αμ, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained αμ = [116592089（63）] × 10^-11 ±0.54 ppm. The last digit of a, is changed from the published value owing to a new value of the ratio of the muon-to-proton magnetic moment that has become available. At present there appears to be a difference between the Standard-Model value and the measured value, at the ≌ 3 standard deviation level when electron-positron annihilation data are used to determine the lowest-order hadronic piece of the Standard Model contribution. The improved experiment, along with further advances in the determination of the hadronic contribution, should clarify this difference. Because of its ability to constrain the interpretation of discoveries made at the LHC, the improved measurement will be of significant value, whatever discoveries may come from the LHC.

Muon g-2 discrepancy:new physics or a relatively light Higgs?

After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In particular, a hypothetical increase of the hadroproduction cross section in low-energy e^＋e^- collisions could bridge the muon g-2 discrepancy, but it is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 135 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.

Neutrino masses,leptonic flavor mixing,and muon(g−2)in the seesaw model with the U(1)L_(μ)-L_(r)gauge symmetry

The latest measurements of the anomalous muon magnetic moment a_(μ)≡(g_(μ)-2)/2show a 4:2σdiscrepancy between the theoretical prediction of the Standard Model and the experimental observations.To account for such a discrepancy,we consider a possible extension of the type-(I+II)seesaw model for neutrino mass generation with a gauged L_(μ)-L_(r)symmetry.By explicitly constructing an economical model with only one extra scalar singlet,we demonstrate that the gauge symmetry U(1)L_(μ)-L_(r)and its spontaneous breaking are crucial not only for explaining the muon result but also for generating the neutrino masses and leptonic flavor mixing.Various phenomenological implications and experimental constraints on the model parameters are also discussed.