Muon g - 2 in the Littlest Higgs Model

In this paper the anomalous magnetic dipole moment of muon 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, mixing angles c and cˊ, and the Higgs triplet vacuum expectation value vˊ 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 Δa_μ from 2.6σ for the SM to 2.5σ for the LH model.     

Extra matters decree the relatively heavy Higgs of mass about 125 GeV in the supersymmetric model

We show that the Higgs mass about 125 GeV is easily realized in supersymmetric model with extra matters, simultaneously explaining the anomaly in the muon anomalous magnetic moment and the dark matter density.     

The muon anomalous magnetic moment from a generic charged Higgs with SUSY

We study the contribution of a generic charged Higgs (H⁺) to the muon anomalous magnetic moment a_μ with the SUSY soft breaking parameters. We find out that the deviation between the experimental data and the predicted SM value on a_μ can be explained by the two-loop charged Higgs diagrams even with m_H⁺∼400 GeV.     

Low energy constraints on N = 2 supersymmetric models

We derive constraints on the masses of mirror particles in N = 2 supersymmetric theories. We consider the K_L?K_S mass difference, the π → ev/π → μv branching ratio and the anomalous magnetic moment of the muon. The K_L?K_S mass difference gives a lower bound of 15 TeV on the mirror gauge scalar and mirror gauge fermion masses, under suitable assumptions.     

Effect of the neutrino magnetic moment on the properties of the muon

The effect of the neutrino dipole magnetic moment on the properties of the muon is investigated within the standard model of electroweak interactions and a model based on the SU(2) _L × SU(2) _R × U(1) _B-L gauge group (left-right model). In the case of the Dirac neutrino, muon decay through the channel µ^? → e ^?γ is studied with allowance for the neutrino dipole magnetic moment. It is shown that, both in the standard model supplemented with an SU(2) _L right-handed neutrino singlet and in the standard model featuring two doublets of Higgs fields, radiative muon decay is unobservable. In the left-right model, the contributions of diagrams associated with the neutrino dipole magnetic moment become significant only in the case of a mutual compensation of the contributions of diagrams involving the electromagnetic vertices of charged gauge bosons and singly charged Higgs bosons. At specific values of the parameters of the left-right model, one can then obtain an experimental upper limit on the branching fraction of this reaction. The contributions of the neutrino dipole magnetic moment to the muon anomalous magnetic moment are found for the Dirac and the Majorana neutrino. It is established that, both in the standard model and in the left-right model, values of the neutrino anomalous magnetic moment that are required for explaining the (g ? 2)_µ anomaly are in excess of the theoretical predictions for this moment.     

An interpolation of the vacuum polarization function for the evaluation of hadronic contributions to the muon anomalous magnetic moment

We propose a simple parameterization of the two-point correlator of hadronic electromagnetic currents for the evaluation of the hadronic contributions to the muon anomalous magnetic moment. The parameterization is explicitly done in the Euclidean domain. The model function contains a phenomenological parameter which provides an infrared cutoff to guarantee the smooth behavior of the correlator at the origin in accordance with experimental data in e ⁺e^- annihilation. After fixing a numerical value for this parameter from the leading order hadronic contribution to the muon anomalous magnetic moment, the next-to-leading order results related to the vacuum polarization function are accurately reproduced. The properties of the four-point correlator of hadronic electromagnetic currents as for instance the so-called light-by-light scattering amplitude relevant for the calculation of the muon anomalous magnetic moment are briefly discussed. Received: 14 December 2001 / Published online: 7 June 2002     

Low energy supergravity and the anomalous magnetic moment of the muon

The anomalous magnetic moment of the muon (g ? 2)_μ imposes constraints on the masses and mixings of spin-zero leptons, gauge fermions, and Higgs fermions in minimal models of low energy supergravity. We demonstrate that there exist only limited values of the parameters in these models that are ruled out by existing limits on (g ? 2)_μ.     

Muon anomalous magnetic moment in the supersymmetric economical 3-3-1 model

We investigate the muon anomalous magnetic moment in the context of a supersymmetric version of the economical 3-3-1 model. We compute the 1-loop contribution of superpartner particles. We show that the contribution of superparticle loops become significant when tanγ is large. We investigate the cases of both small and large values of tanγ. We find the region of the parameter space where the slepton masses of a few hundred GeV are favored by the muon g–2 for small tanγ (tanγ ≈ 5). Numerical estimation gives the mass of supersymmetric particles, the mass of gauginos m _G ≈ 700 GeV, and the light slepton mass \(m_{\tilde L} \) of the order of O (100) GeV. When tanγ is large (tanγ ≈ 60), the charged slepton mass \(m_{\tilde L} \) and the gaugino mass m _G are O(1) TeV, while the sneutrino mass ≈450 GeV is in the reach of the LHC.     

New definition for the hadronic contribution to the muon anomalous magnetic moment

A new definition is proposed for the hadronic contribution to the muon anomalous magnetic moment that is based on the inclusion of the effects of vacuum polarization by leptons into the cross section for one-photon annihilation of a lepton pair into hadrons. The formula for the hadronic contribution includes the convolution of the measured cross section for annihilation into hadrons with a certain standard function. This remark concerns radiative correction to this function. A particular form has been proposed for this correction. It has been shown that the use of the new function makes it possible to reduce the uncertainty in such contributions due to radiative correctioins to δa _h/a _h ～ 10^?4.     

Anomalous magnetic moment of the muon in the left-right model

The effect of Higgs bosons on the anomalous magnetic moment of the muon is considered within the model that is based on the SU(2)_L×SU(2)_R×U(1)_B–L gauge group and which involves a bidoublet and two triplets of Higgs fields (left-right model). For the Yukawa coupling constants and the masses of Higgs bosons, the regions are found where the model leads to agreement with experimental results obtained at the Brookhaven National Laboratory (BNL) for the anomalous magnetic moment of the muon. In order to explore corollaries from the constraints obtained for the parameters of the Higgs sector, the processes e⁺e^? → μ⁺μ^?, τ⁺τ^? and μ⁺μ^? → μ⁺μ^?, τ⁺τ^? are considered both within the left-right model and within the model involving two Higgs doublets (two-Higgs-doublet model). It is shown that, if the mass of the lightest neutral Higgs boson does indeed lie in the range 3.1–10 GeV, as is inferred from the condition requiring the consistency of the two-Higgs-doublet model with the data of the BNL experiment, this Higgs boson may be observed as a resonance peak at currently operating e⁺e^? colliders (VEPP-4M, CESR, KEKB, PEP-II, and SLC). In order to implement this program, however, it is necessary to reduce considerably the scatter of energy in the e⁺ and e^? beams used, since the decay width of the lightest neutral Higgs boson is extremely small at such mass values. It is demonstrated that, in the case of the left-right model, for which the mass of the lightest neutral Higgs boson is not less than 115 GeV, the resonance peak associated with it may be detected at a muon collider.     

Neutrino magnetic moment inN=1 minimal supergravity

The complete one-loop supersymmetric (SUSY) correction to the magnetic moment (NMM) of a Dirac neutrino is calculated with allowance for mixing between the scalar leptons and for mixing between theW-gaugino and Higgs fermions. The contribution from the charged Higgs loop is negligible for all practical purpose. We thoroughly study the dependence of NMM on the SUSY parameters. The SUSY contribution to the NMM can be a few times less than or comparable to the value of the standard model (with a right-handed neutrino singlet added). The SUSY correction to the NMM increases with decreasing β value (tan β=〈H ₂〉/〈H ₁〉), and is not very sensitive to the charged scalar lepton mass.     

Can extra dimensions accessible to the SM explain the recent measurement of anomalous magnetic moment of the muon?

We investigate whether models with flat extra dimensions in which SM fields propagate can give a significant contribution to the anomalous magnetic moment of the muon (MMM). In models with only SM gauge and Higgs fields in the bulk, the contribution to the MMM from Kaluza–Klein (KK) excitations of gauge bosons is very small. This is due to the constraint on the size of the extra dimensions from tree-level effects of KK excitations of gauge bosons on precision electroweak observables such as Fermi constant. If the quarks and leptons are also allowed to propagate in the (same) bulk (“universal” extra dimensions), then there are no contributions to precision electroweak observables at tree-level. However, in this case, the constraint from one-loop contribution of KK excitations of (mainly) the top quark to T parameter again implies that the contribution to the MMM is small. We show that in models with leptons, electroweak gauge and Higgs fields propagating in the (same) bulk, but with quarks and gluon propagating in a sub-space of this bulk, both the above constraints can be relaxed. However, with only one Higgs doublet, the constraint from the process b→sγ requires the contribution to the MMM to be smaller than the SM electroweak correction. This constraint can be relaxed in models with more than one Higgs doublet.     

Frequentist analysis of the parameter space of minimal supergravity

We make a frequentist analysis of the parameter space of minimal supergravity (mSUGRA), in which, as well as the gaugino and scalar soft supersymmetry-breaking parameters being universal, there is a specific relation between the trilinear, bilinear and scalar supersymmetry-breaking parameters, A ₀=B ₀+m ₀, and the gravitino mass is fixed by m _3/2=m ₀. We also consider a more general model, in which the gravitino mass constraint is relaxed (the VCMSSM). We combine in the global likelihood function the experimental constraints from low-energy electroweak precision data, the anomalous magnetic moment of the muon, the lightest Higgs boson mass M _h , B physics and the astrophysical cold dark matter density, assuming that the lightest supersymmetric particle (LSP) is a neutralino. In the VCMSSM, we find a preference for values of m _1/2 and m ₀ similar to those found previously in frequentist analyses of the constrained MSSM (CMSSM) and a model with common non-universal Higgs masses (NUHM1). On the other hand, in mSUGRA we find two preferred regions: one with larger values of both m _1/2 and m ₀ than in the VCMSSM, and one with large m ₀ but small m _1/2. We compare the probabilities of the frequentist fits in mSUGRA, the VCMSSM, the CMSSM and the NUHM1: the probability that mSUGRA is consistent with the present data is significantly less than in the other models. We also discuss the mSUGRA and VCMSSM predictions for sparticle masses and other observables, identifying potential signatures at the LHC and elsewhere.     

Letter: Antisymmetric Tensor Contribution to the Muon g − 2

We investigate the Kalb-Ramond antisymmetric tensor field as a solution to the muon g – 2 problem. In particular we calculate the lowest-order Kalb-Ramond contribution to the muon anomalous magnetic moment and find that we can fit the new experimental value for the anomaly by adjusting the coupling without affecting the electron anomalous magnetic moment results.     

Contributions to the muon’s anomalous magnetic moment from a hidden sector

The measurement of the anomalous magnetic moment of the muon provides a stringent test of the standard model and of any physics that lies beyond it. There is currently a deviation of 3.1σ between the standard model prediction for the muon’s anomalous magnetic moment and its experimental value. We calculate the contribution to the anomalous magnetic moment in theories where the muon couples to a particle in a hidden sector (that is, uncharged under the standard model) and a connector (which has nontrivial standard model gauge and hidden sector quantum numbers).     

Indirect methods for determining heavy-neutrino masses

Within the two-flavor approximation, equations that relate the oscillation parameters for both light and heavy neutrinos to the Yukawa coupling constants and the vacuum expectation values of the Higgs fields are derived within the left-right model. The contributions from Higgs bosons to the muon anomalous magnetic moment, to the cross sections for lepton-flavor-violating processes, and to the cross sections for low-energy light-neutrino scattering are studied in order to determine the Yukawa coupling constants. It is shown that the heavy-neutrino masses $m_{N_{1,2} } $ can be expressed in terms of only the triplet Yukawa coupling constants and the mass of the gauge boson W ₂. Data on direct and inverse muon decay and constraints on the masses of the $\tilde \delta ^{( - )} , \Delta _{1,2}^{( - - )} $ and W ₂ bosons are used to obtain bounds on $m_{N_{1,2} } $ both in the absence of degeneracy and in the presence of mass degeneracy in the sector of heavy neutrinos. Only in the case of degeneracy are data concerning the explanation of the (g ? 2)_μ anomaly used to determine bounds on $m_{N_{1,2} } $ .     

Standard model Higgs field and energy scale of gravity

The effective potential of the Higgs scalar field in the Standard Model may have a second degenerate minimum at an ultrahigh vacuum expectation value. This second minimum then determines, by radiative corrections, the values of the top-quark and Higgs-boson masses at the standard minimum corresponding to the electroweak energy scale. An argument is presented that this ultrahigh vacuum expectation value is proportional to the energy scale of gravity, E _Planck ≡ √?c ⁵/G _N, considered to be characteristic of a spacetime foam. In the context of a simple model, the existence of kink-type wormhole solutions places a lower bound on the ultrahigh vacuum expectation value and this lower bound is of the order of E _Planck.     

Electric dipole moment for supersymmetric monopoles

The electric dipole moment for the monopoles that can be present in N = 2 and N = 4 supersymmetric SU(2) gauge theories, spontaneously broken by imposing a non-zero expectation value of a scalar field at infinity, is determined by considering the response to a weak external electric field. The magnetic g factor g_M = 2 which is in accord with the duality conjecture of Montonen and Olive.     

Muon anomalous magnetic moment: A consistency check for the next-to-leading-order hadronic contributions

A duality-inspired model for verifying a consistency of the evaluation of the next-to-leadingorder hadronic contributions to the muon anomalous magnetic moment with that of the leading-order ones is proposed. A part of the next-to-leading-order hadronic contributions related to the photon vacuum polarization function is rather accurately reproduced in the model. I find a new numerical value for the light-by-light hadronic contribution that leads to the agreement of the Standard Model theoretical prediction for the muon anomalous magnetic moment with the recent experimental result.     

Exact holography of the mass-deformed M2-brane theory

We test the holographic relation between the vacuum expectation values of gauge invariant operators in \({\mathcal {N}} = 6\) U\(_k(N)\times \mathrm{U}_{-k}(N)\) mass-deformed ABJM theory and the LLM geometries with \({\mathbb {Z}}_k\) orbifold in 11-dimensional supergravity. To do so, we apply the Kaluza–Klein reduction to construct a 4-dimensional gravity theory and implement the holographic renormalization procedure. We obtain an exact holographic relation for the vacuum expectation values of the chiral primary operator with conformal dimension \(\Delta = 1\), which is given by \(\langle {\mathcal {O}}^{(\Delta =1)}\rangle = N^{\frac{3}{2}} \, f_{(\Delta =1)}\), for large N and \(k=1\). Here the factor \(f_{(\Delta )}\) is independent of N. Our results involve an infinite number of exact dual relations for all possible supersymmetric Higgs vacua and so provide a non-trivial test of gauge/gravity duality away from the conformal fixed point. We extend our results to the case of \(k\ne 1\) for LLM geometries represented by rectangular-shaped Young diagrams. We also discuss the exact mapping of the gauge/gravity at finite N for classical supersymmetric vacuum solutions in field theory side and corresponding classical solutions in gravity side.