Eduardo De Rafael
These pages, based on my talk at the Montpellier 14th International Conference in QCD, provide us with a short update of the Standard Model contributions to the Muon Anomalous Magnetic Moment.
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I review the recent calculations and present status of the hadronic light-by-light contribution to the muon g-2.
Contributions of hadronic effects to the muonium physics and anomalous magnetic moment of muon are considered. Special attention is paid to higher-order effects and the uncertainty related to the hadronic contribution to the hyperfine structure interval in the ground state of muonium.
We give an update on the status of the hadronic light-by-light scattering contribution to the muon g-2. We review recent work by various groups, list some of the open problems and give an outlook on how to better control the uncertainty of this contribution. This is necessary in order to fully profit from planned future muon g-2 experiments to test the Standard Model. Despite some recent developments, we think that the estimate a_{mu}^{HLbL} = (116 \pm 40) x 10^{-11} still gives a fair description of the current situation.
We review the present status of the theoretical evaluation of the anomalous magnetic moment of the the muon within the Standard Model. We mainly focus on the hadronic contributions in the muon g-2 due to vacuum polarization effects, light-by-light scattering and higher order electroweak corrections. We discuss some recent calculations together with their uncertainties and limitations and point out possible improvements in the future. In view of the inconsistent values for the hadronic vacuum polarization based on e^+ e^- and tau data, no conclusion can be drawn yet, whether the apparent discre…
The theoretical status of the muon anomaly is reviewed including the recent change in the light by light hadronic correction. Specific attention is given to the implications of the shift in the difference between the BNL experimental result and the standard model prediction for sparticle mass limits. The implication of the BNL data for Yukawa unification is discussed and the role of gaugino mass nonuniversalities in the satisfaction of Yukawa unification is explored. An analysis of the BNL constraint for the satisfaction of the relic density constraint and for the search for dark matter is als…
We analyze allowed region of muon anomalous magnetic moment (muon $g-2$), satisfying lepton flavor violations, $Z$ boson decays, and collider physics, in a framework of multi-charged particles. Then we explore the typical size of the muon $g-2$, and discuss which modes dominantly affect muon $g-2$.
These notes, based on the lectures delivered at the 2003 Schladming School of Theoretical Physics, provide an introduction to the theory of the anomalous magnetic moments of the muon and of the electron.
We study the the electroweak symmetry breaking induced by the interaction of unparticles and the SM Higgs with an additional complex scalar. Furthermore, we estimate the contribution of the mixing scalars on the muon anomalous magnetic moment. We observe that this contribution is at least two order less than the discrepancy between the experimental and the SM results of the muon anomalous magnetic moment.
We explore the possibility of the existence of excited leptons in the light of recent data on muon $g - 2$ from BNL. We have been able to put stringent bounds on the relevant parameter space.
Some short-distance properties of the fourth-rank hadronic vacuum polarization tensor are re-examined.Their consequences are critically discussed in the context of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon.
We calculate the new physics effects on the anomalous magnetic moment of the muon in the framework of the two Higgs doublet model. We predict an upper bound for the lepton flavor violating coupling, which is responsible for the point like interaction between muon and tau, by using the uncertainty in the experimental result of the muon anomalous magnetic moment. We show that the upper bound predicted is more stringent compared to the one which is obtained by using the experimental result of the muon electric dipole moment
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).
It is shown that a minimal extension of the standard model with leptons that transform as singlets under the SU(2) symmetry of weak interactions can explain the recently reported derivation in the measured value of the anomalous magnetic moment of the muon from that expected in the standard model.
The experimental method together with the analysis method and results of the data taken in 2000 and prospects of the muon anomalous magnetic and electric dipole moment experiments are presented here.
We use Pade Approximants to obtain improved predictions for the anomalous magnetic moments of the electron and the muon. These are needed because of the very precise experimental values presently obtained for the electron, and soon to be obtained at BNL for the muon. The Pade prediction for the QED contribution to the anomalous magnetic moment of the muon differs significantly from the naive perturbative prediction.
The leptons are viewed as composite objects, exhibiting anomalous magnetic moments and anomalous flavor-changing transition moments. The decay $μ\to e γ$ is expected to occur with a branching ratio of the same order as the present experimental limit.
We computed the hadronic vacuum-polarization contributions to the muon anomalous magnetic moment $a_μ(hadr.)$ by using the QCD model with infinite number of vector mesons [1,2]. The result is $a_μ(hadr.) = 663(23) \times 10^{-10}$. }
The current status of the Standard Model prediction for the anomalous magnetic moment of the muon is briefly reviewed and compared with the present experimental value.
We calculate the anomalous magnetic moment for muons at one loop level arising from left right symmetric excited leptons which are excited states of known standard model leptons. Such excited states arise in compositeness theories where the known leptons are assumed to be made of more fundamental particles. In this work, we assume that the excited leptons possess a left right symmetry also. We show that at the one loop level, the QED contribution to the muon anomalous magnetic moment from these excited leptons comes from only one Feynman diagram, which turns out to be a natural analog of the o…
The current status of the muon anomalous magnetic moment problem is briefly presented. The corrections to muon anomaly coming from the effects of hadronic vacuum polarization, Z*γγ* effective vertex and light-by-light scattering are estimated within the instanton model of QCD vacuum.
The recent result from the E821 experiment at BNL on the anomalous magnetic moment of the muon shows a distinct discrepancy with the Standard Model predictions. We calculate the additional correction that the anomalous magnetic moment receives in a model with scalar leptoquarks. We find that such models can account for the deviation from the SM value even for small leptoquark couplings.
A very economic scenario with just three extra scalar fields beyond the Standard Model is invoked to explain the muon anomalous magnetic moment, the requisite relic abundance of dark matter as well as the Xenon-1T excess through the inelastic down-scattering of the dark scalar.
Interaction of charged leptons with photons is considered for the case when one of the lepton legs is off the mass shell. The effect due to off-mass-shell shift in the anomalous magnetic moment is computed within one-loop approximation. Possible contributions of this effect in the muon $g-2$ measurements are discussed.
We present an analytic calculation of electron and tau O(alpha^3) loop effects on the muon anomalous magnetic moment. Computation of such three-loop diagrams with three mass scales is possible using asymptotic and eikonal expansions. An evaluation of a new type of eikonal integrals is presented in some detail.
We review the present status of the hadronic light-by-light contribution to muon g-2 and critically compare recent calculations.
I present a fairly detailed discussion of various contributions to the anomalous magnetic moment of the muon a_mu. I try to give an unbiased evaluation of the validity of the SM prediction for this quantity and to point out some delicate issues involved in its calculation. I conclude that the theory uncertainties in the SM prediction for the muon anomalous magnetic moment are underestimated and a great deal of work will be required to reduce these uncertainties to the level required by experiment.
We present the status of the MUonE experimental proposal which aims at determining the leading order hadronic contribution to the muon g-2 by measuring the hadronic part of the photon vacuum polarization in the space-like region.
Status of the superweak extension of the standard model and muon g-2
本文综述了标准模型超弱U(1)扩展的唯象学现状，该模型旨在同时解释中微子质量、暗物质、宇宙暴胀、电弱真空稳定性和轻子生成，并给出了可行方案。
A model for verifying a consistency of the next-to-leading order hadronic contributions to the muon anomalous magnetic moment with those of the leading order is proposed. A part of the next-to-leading order hadronic contributions related to the vacuum polarization is rather accurately reproduced in the model. I find a new numerical value for the light-by-light hadronic contribution that leads to agreement with recent experimental result for the muon anomalous magnetic moment.
We review the current status of theoretical calculations of the hadronic light-by-light scattering contribution to the muon anomalous magnetic moment. Different approaches and related issues such as OPE constraints and large breaking of chiral symmetry are discussed. Combining results of different models with educated guesses on the errors we come to the estimate $$a^{\rm HLbL}=(10.5\pm 2.6)\times 10^{-10}.$$ The text is prepared as a contribution to the {\it Glasgow White Paper on the present status of the Muon Anomalous Magnetic Moment}.
An automatic system to calculate two loop weak corrections to muon anomalous magnetic moment is discussed. Diagrams are classified into eight types, according to their topology. Adopting Civitanović-Kinoshita representation of Feynman amplitude and using the topological property, the renormalization is performed consistently by n-dimensional regularization method.
The impact of the X17 boson on particle physics anomalies: muon anomalous magnetic moment, Lamb shift, W mass and dark charges
本研究考察X17矢量玻色子对μ子/电子反常磁矩及μ子Lamb位移的解释作用，并依据最新W玻色子质量数据约束其与标准模型U(1)_Y规范玻色子的动力学混合。
We derive an analytic result for the pion pole contribution to the light-by-light scattering correction to the anomalous magnetic moment of the muon, $a_μ= (g_μ-2)/2$. Using the vector meson dominance model (VMD) for the pion transition form factor, we obtain $a_μ^{{\rm LBL},π^0} = +56 \times 10^{-11}$.
We propose a standard model minimal extension with two lepton weak SU(2) doublets and a scalar singlet to explain the deviation of the measured anomalous magnetic moment of the muon from the standard model expectation. This scheme can be naturally motivated in string inspired models such as E_6 and AdS/CFT.
I review the present Standard Model prediction of the muon anomalous magnetic moment. The discrepancy with its experimental determination is (25.5 +- 8.0) x 10^-10, i.e., 3.2 standard deviations.
With the recent interest in the measured and standard model values of the muon anomalous magnetic moment, a_mu, some confusion has arisen concerning our knowledge of the hadronic contribution to a_mu. In the dispersion integral approach to hadronic vacuum polarization effects, low energy contributions must be evaluated from data or in a model-dependent approach tested by data. At higher energies perturbative QCD has been used, sometimes in conjunction with data. The history of such evaluations is reviewed, and the prospects for further improvement are discussed. We conclude that not all publis…
The muon anomalous magnetic dipole moment (MDM) is calculated in the framework of the minimal supersymmetric standard model (MSSM). In this paper, we discuss how the muon MDM depends on the parameters in MSSM in detail. We show that the contribution of the superparticle-loop becomes significant especially when $\tanβ$ is large. Numerically, it becomes $O(10^{-8}-10^{-9})$ in a wide parameter space, which is within the reach of the new Brookhaven E821 experiment.
We propose the novel lepton-number relationship $L_τ= L_e + L_μ$, which is uniquely realized by the interaction $(\hat ν_e \hat μ- \hat e \hat ν_μ) \hat τ^c$ in supersymmetry and may account for a possibly large muon anomalous magnetic moment. Neutrino masses (with bimaximal mixing) may be generated from the spontaneous and soft breaking of this lepton symmetry.
No gauge invariant regularization is available for the perturbative calculation of the standard model. One has to add finite counter terms to restore gauge symmetry for the renormalized amplitudes. The muon anomalous magnetic moment can be accurately measured but the experimental result does not entirely agree with the theoretical calculation from the standard model. This paper is to compute the contributions to the muon gyromagnetic ratio $g_μ$ due to the finite counter terms. The result obtained is found to be far from sufficient to explain the discrepancy between theory and experiment.
The current status of electroweak radiative corrections to the muon anomalous magnetic moment is discussed. Asymptotic expansions for some important electroweak two loop top quark triangle diagrams are illustrated and extended to higher order. Results are compared with the more general integral representation solution for generic fermion triangle loops coupled to pseudoscalar and scalar bosons of arbitrary mass. Excellent agreement is found for a broader than expected range of mass parameters.
We investigate the status of models containing exotic fermions or extra Z-like neutral gauge bosons in the light of the recent data on anomalous magnetic moment of muon. We find that it is possible to extract interesting bounds on the parameters characterizing such models. The bounds are particularly strong if the new flavour-changing neutral currents are axial vectorlike.
We show that a proposal which involves an effective radius derived from an effective potential that includes a linear extra-potential may solve both the proton and deuteron size puzzle. Moreover, this solution preserves the e-μ universality and helps to solve the anomalous magnetic moment of the muon too. Still, it is consistent with the rms magnetic radius of the proton and deuteron, the rms charge radius of both the ordinary and muonic C12 as well as the kaonic and pionic X-rays spectroscopy.
We investigate some proposals to solve the electric charge quantization puzzle, which simultaneously explain the recent measured deviation on the muon anomalous magnetic moment. For this we assess extensions of the Electro-Weak Standard Model spanning modifications on the scalar sector only. It is interesting to verify that one can have modest extensions which easily account for the solution for both problems.
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 $m_{H^+}\sim 400 GeV$.
We classify all possible one-particle (scalar and fermion) extensions of the Standard Model that can contribute to the anomalous magnetic moment of leptons. We review the cases already discussed in the literature and complete the picture by performing the calculation for a fermionic doublet with hypercharge -3/2. We conclude that, out of the listed possibilities, only two scalar leptoquarks and the pseudoscalar of a peculiar two-Higgs-doublet model could be the responsibles for the muon anomalous magnetic moment discrepancy. Were this the case, this particles could be seen in the next LHC run.…
In this contribution recent developments are discussed which lead to a significant reduction of the error for $α(M_Z^2)$ and $(g-2)_μ$.
We review the status of the hadronic light-by-light contribution to the muon anomalous magnetic moment and critically compare recent calculations. We also study in detail which momentum regions the pi^0 exchange main contribution originates. We also argue that a_μ^{light-by-light} = (11 \pm 4) \times 10^{-10} encompasses the present understanding of this contribution and comment on some directions to improve on that.
The evidence for dark matter signals a new class of particles at the TeV scale, which may manifest themselves indirectly through loop effects. In a simple model we show that these loop effects may be responsible for the enhanced muon anomalous magnetic moment, for the neutrino mass, as well as for leptogenesis in a novel way. This scenario can be verified at LHC experiments.
Theoretical calculations of the hadronic contribution to the muon anomalous magnetic moment utilize experimental data from e+e- annhilation and tau decay. The data provide input to a dispersion relation. I contend that it is not possible to put error bounds on the dispersion-relation calculation absent proof - not presently available - that the amplitudes in question are polynomially bounded. Examples are provided. Additional pertinent references have been added to an earlier version of this posting.
The numerically dominant QED contributions to the anomalous magnetic moment of the muon stem from Feynman diagrams with internal electron loops. We consider such corrections and present a calculation of the four-loop light-by-light-type corrections where the external photon couples to a closed electron or muon loop. We perform an asymptotic expansion in the ratio of electron and muon mass and reduce the resulting integrals to master integrals which we evaluate using analytical and numerical methods. We confirm the results present in the literature which are based on different computational met…
In this talk we review the recent progress on the numerical determination of the Hadronic Light-by-Light contribution to the anomalous magnetic moment of the muon and we discuss the role of experimental data on the accuracy of its determination. Special emphasis on the main contribution, the pseudoscalar piece, is made. Gathering recent progress in the light-by-light scattering contribution we consider $a_μ^{\mathrm{HLBL}} = (12.1\pm3.0)\times10^{-10}$ as a good summary of the state-of-the-art calculations which still claims for a $4σ$ deviation between theory and experiment for the $(g-2)_μ$.
Introducing a leptonic U(1) gauge symmetry, we try to reproduce the gap in the cosmic neutrino spectrum reported by the IceCube collaboration, and at the same time, make an additional contribution to the muon anomalous magnetic moment, which fills the gap between the standard model prediction and the experimental observation.
The dominant theoretical uncertainties in both, the anomalous magnetic moment of the muon and the value of the electromagnetic coupling at the Z scale arise from their hadronic contributions. Since these will ultimately dominate the experimental errors, we study the correlation between them, as well as with other fundamental parameters. To this end we present analytical formulas for the QCD contribution from higher energies and from heavy quarks. Including these correlations affects the Higgs boson mass extracted from precision data.
Using the approach based on Bogoliubov compensation principle is applied to calculation of a contribution to the muon $g-2$. Using the previous results on spontaneous generation of the effective anomalous three-boson interaction we calculate the contribution, which proves to agree with the well-known discrepancy. The calculated quantity contains no adjusting parameters but the experimental values for the muon and the W-boson masses. The result can be considered as a confirmation of the approach.
We present the results of the influence of the minimal supersymmetric standard model extended by an additional Higgs singlet N, with vacuum expectation value $v_N$, on the anomalous magnetic moment of the muon. This gives different mass matrices for the charginos and neutralinos, which are taken into account within the relevant penguin diagrams leading to a contribution $Δa_μ$\ to the anomalous magnetic moment of the muon. We show that a large vacuum expectation value for the Higgs singlet leads to a suppression of the supersymmetric contribution making it difficult to see in an experiment in …
About 3 sigma deviation from the standard model prediction of muon anomalous magnetic moment (muon g-2) has been reported. We consider new physics beyond the standard model which has new Yukawa interactions with muon. We compute new contributions to muon g-2 and corrections to electroweak observables, and show the consistent region of parameter space. We find that in a simple model where the chirality flip of muon occurs only in the external muon line in one-loop muon g-2 diagrams, it is necessary to introduce the relatively large new Yukawa coupling and the electroweak scale new particles. On…
The definition of the physical properties of particles in perturbative gauge theories must satisfy gauge invariance as a requisite. The Pinch Technique provides a framework to define the electromagnetic form factors and the electromagnetic static properties of fundamental particles in a consistent and gauge-invariant form. We apply a simple prescription derived in this formalism to check the calculation of the gauge-invariant one-loop bosonic electroweak corrections to the muon anomalous magnetic moment.
We propose a simple unified description of two recent precision measurements which suggest new physics beyond the Standard Model of particle interactions, i.e. the deviation of $\sin^2 θ_W$ in deep inelastic neutrino-nucleon scattering and that of the anomalous magnetic moment of the muon. Our proposal is also consistent with a third precision measurement, i.e. that of parity nonconservation in atomic Cesium, which agrees with the Standard Model.
The two-loop electroweak corrections to the anomalous magnetic moment of the muon, generated by fermionic loops, are calculated. An interesting role of the top quark in the anomaly cancellation is observed. New corrections, including terms of order $G_μαm_t^2$, are computed and a class of diagrams previously thought to vanish are found to be important. The total fermionic correction is $-(23\pm 3) \times 10^{-11}$ which decreases the electroweak effects on $g-2$, predicted from one-loop calculations, by 12\%. We give an updated theoretical prediction for $g-2$ of the muon.
The effective supersymmetric theory (ESUSY) with R parity conservation cannot give a large anomalous magnetic moment of $μ$. It is pointed out that the flavor conservation and a large $(g-2)_μ$ within the experimental limits are achievable in the ESUSY with R parity violating couplings involving the third generation superparticles.
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