The anomalous magnetic moment of the top quark may be measured during the first run of the LHC at 7 TeV. For these measurements, it will be useful to have available tree amplitudes with ttbar and arbitrarily many photons and gluons, including both QED and color anomalous magnetic moments. In this paper, we present a method for computing these amplitudes using the Britto-Cachazo-Feng-Witten (BCFW) recursion formula. Because we deal with an effective theory with higher-dimension couplings, there are roadblocks to a direct computation with the BCFW method. We evade these by using an auxiliary scalar theory to compute a subset of the amplitudes.
The anomalous magnetic moment of the muon is evaluated in the D-brane realization of the Standard Model. It is pointed out that the massive anomalous U(1) gauge bosons predicted, give extra contributions that are compatible with current experimental data.
We discuss nonminimal couplings of fermions to the electromagnetic field, which generically appear in models with extra dimensions. We consider models where the electromagnetic field is generated by the Kaluza-Klein mechanism. The nonminimal couplings contribute at tree-level to anomalous magnetic and electric dipole moments of fermions. We use recent measurements of these quantities to put limits on the parameters of models with extra dimensions.
We compute the non-planar contribution to the anomalous dimension of the eight moment of the twist-2 operators in N=4 supersymmetric Yang-Mills theory at four loops. This result was obtained from the calculations of some elements of the anomalous dimension matrix for twist-2 operators with the help of a relations between its elements and eigenvalues. The properties of the obtained result and a possible relations with a planar results are discussed.
We present the result of a calculation for the third and fourth moments of the non-singlet four-loop anomalous dimension of Wilson twist-2 operators in QCD with full color and flavour structures. We discuss also a general expressions for some contributions to the full four-loop anomalous dimension obtained with the help of the method, based on LLL-algorithm, which was proposed earlier by us for the reconstruction of a general form of the anomalous dimension from a fixed values.
We present the result of a full direct component calculation for the first three even moments of the non-planar contribution into the four-loop anomalous dimension of twist-2 operators in maximally extended N=4 supersymmetric Yang-Mills theory. Obtained result complete our previous calculations in arXiv:0902.4646 and gives the usual result for the higher moments on the contrary to degenerate one in the case of Konishi. We have proposed a general form of zeta(5) and zeta(3) parts of the full non-planar anomalous dimension of twist-2 operators. As by product, we have obtained the first moment of…
The recently reported measurement of the muon's anomalous magnetic moment differs from the standard model prediction by 2.6 standard deviations. We examine the implications of this discrepancy for supersymmetry. Deviations of the reported magnitude are generic in supersymmetric theories. Based on the new result, we derive model-independent upper bounds on the masses of observable supersymmetric particles. We also examine several model frameworks. The sign of the reported deviation is as predicted in many simple models, but disfavors anomaly-mediated supersymmetry breaking.
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 derive an inequality for the distribution of quarks with non-zero orbital angular momentum, and thus demonstrate, in a model-independent way, that a non-vanishing anomalous magnetic moment requires both a non-zero size of the target as well as the presence of wave function components with quark orbital angular momentum L_z>0.
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.
By using the anomalous magnetic and electric dipole moments of the $τ$ lepton in an effective lagrangian approach to the new physics, we investigate the lepton flavor violation (LFV) decays, $l\to l'γ$, and $μ,τ$ anomalous magnetic and electric dipole moments in a lepton mass matrices ansatz which induced by SUSY GUT. We put very stringent constraints LFV decays and $τ$ anomalous magnetic and electric dipole moments.
We compute the contributions to the electron and muon anomalous magnetic moment induced by heavy leptons up to four-loop order. Asymptotic expansion is applied to obtain three analytic expansion terms which show rapid convergence.
We describe modifications made to KORALZ version 4.03 in order to allow for anomalous magnetic and electric dipole moments of the tau. We discuss the verification of the method at LEP 1 energies.
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.
By the Schwinger proper-time method, the one-loop contribution to the anomalous magnetic moment of the W-boson is calculated at high temperature. It is shown that the value of AMM is positive and depends linearly upon temperature.
In the case of massless current quarks we find that the breaking of chiral symmetry usually triggers the generation of an anomalous magnetic moment for the quarks. We show that the kernel of the Ward identity for the vector vertex yields an important contribution. We compute the anomalous magnetic moment in several quark models. The results show that it is hard to escape a measurable anomalous magnetic moment for the quarks in the case of spontaneous chiral symmetry breaking.
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.
The same light-front wave functions of the proton are involved in both the anomalous magnetic moment of the nucleon and the Sivers function. Using the diquark model, we derive a simple relation between the anomalous magnetic moment and the Sivers function, which should hold in general with good approximation. This relation can be used to provide constraints on the Sivers single spin asymmetries from the data on anomalous magnetic moments. Moreover, the relation can be viewed as a direct connection between the quark orbital angular momentum and the Sivers function.
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.
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 show that the anomalous magnetic moment of fermion in the gauge-Higgs unification is finite in any spacetime dimensions, which is a new predictive physical observable similar to the Higgs mass.
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).
We present the result of a calculation for the first even moment of the non-singlet four-loop anomalous dimension of Wilson twist-2 operators in QCD with full color and flavor structures.
We compute the anomalous dimensions of the transversity operator at three loops in the MSbar scheme for fixed moment n where n <= 8. The results for the RI' renormalization scheme are also provided for an arbitrary linear covariant gauge for n <= 7.
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.
We propose a generalization of the upgraded Karl- Sehgal formula which relates baryon magnetic moments to the spin structure of constituent quarks, by adding anomalous magnetic moments of quarks. We first argue that relativistic nature of quarks inside baryons requires introduction of two kinds of magnetisms, one axial and the other tensoriel. The first one is associated with integrated quark helicity distributions (standard) and the second with integrated transversity distributions . The weight of each contribution is controlled by the combination of two parameters, xi the ratio of the quark …
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 analyse the process $τ^-\toν_τπ^-π^0$ allowing for anomalous weak charged current magnetic and electric dipole moment interactions and determine the effects on the differential and total decay rates. Using recent experimental data we determine the following values for the anomalous magnetic and electric dipole moment parameters, respectively: $κ= 0.16 \pm 0.08; and |\tildeκ| = 0.88^{+0.25}_{-0.35}.$
The degree of depolarization of neutral particles in crystals can reach tens of percents over the crystal length of several centimeters, which can be the basis for possible experimental application of the depolarization effect for measuring anomalous magnetic moments of short-lived neutral hyperons.
We calculate the contribution to the anomalous magnetic moment of leptons in the type-I and type-III seesaw models. We show that, even if the scale of the new physics is pushed down to the electroweak scale, this contribution is not large enough to explain the measured discrepancy of the muon anomalous magnetic moment.
We consider bound states of fermions with an anomalous magnetic moments in the field of charged cylinder.Also we obtain second order equations for axially symmetric $Z_0(r)$-boson field, radial axially symmetric magnetic field, obtain second order equations for case of bound states of fermions in the radial electric and magnetic fields.
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 $a_μ(hadr.) = 663(23) \times 10^{-10}$. }
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…
We propose an ultimate upgrade of the Karl- Sehgal (KS) formula which relates baryon magnetic moments to the spin structure of constituent quarks, by adding anomalous magnetic moments of quarks. We first argue that relativistic nature of quarks inside baryons requires introduction of two kinds of magnetisms, one axial and the other tensoriel. The first one is associated with integrated quark helicity distributions(standard) and the second with integrated transversity distributions . The weight of each contribution is controlled by the combination of two parameters, the ratio of the quark mass …
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
Violation of chiral symmetry together with change of mass sign allows a linear correction in inverse power of new physics scale to the anomalous magnetic moment of muon. In this light we analyse alternative models showing in particular that grand unification, supersymmetry and muon substructure may explain the discrepancy between the experimental value of the muon anomaly and the standard model calculation.
Using the effective Lagrangian method, we analyze the electroweak corrections to the anomalous dipole moments of lepton from some special two-loop topological diagrams which are composed of neutralino (chargino) - slepton (sneutrino) in the minimal supersymmetric extension of the standard model (MSSM). Considering the translational invariance of the inner loop momenta and the electromagnetic gauge invariance, we get all dimension 6 operators and derive their coefficients. After applying equations of motion to the external leptons, the anomalous dipole moments of lepton are obtained. The numeri…
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.
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.
Using the effective Lagrangian method, we analyze the electroweak corrections to the anomalous dipole moments of lepton from some special two-loop diagrams where a closed neutralino/chargino loop is inserted into relevant two Higgs doublet one-loop diagrams in the minimal supersymmetric extension of the standard model with CP violation. Considering the translational invariance of loop momenta and the electromagnetic gauge invariance, we get all dimension 6 operators and derive their coefficients. After applying equations of motion to the external leptons, we obtain the anomalous dipole moments…
We consider the jet cross sections for gluons coupling to quarks with an anomalous chromomagnetic moment. We then apply this to the deviation and bounds from QCD found in the CDF and D0 Fermilab data, respectively, to find a range of possible values for the anomalous moments. The quadratic and quartic terms in the anomalous moments can fit to the rise of a deviation with transverse energy. Since previous analyses have been done on the top quark total cross section, here we assume the same moment on all quarks except the top and find the range $|κ'| \equiv |κ/(2 m_q)| = 1.0\pm 0.3$ TeV$^{-1}$ f…
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.
Recent results announced as measurements of the muon's anomalous magnetic moment are in fact measurements of the muon's anomalous spin precession frequency. This precession frequency receives contributions from both the muon's anomalous magnetic and electric dipole moments. We note that all existing data cannot resolve this ambiguity, and the current deviation from standard model predictions may equally well be interpreted as evidence for new physics in the muon's anomalous magnetic moment, new physics in the muon's electric dipole moment, or both.
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.
It is shown that the quark-gluon interaction induced by instantons leads to the quark anomalous chromomagnetic moment. In the instanton-liquid model for the QCD vacuum, the chromomagnetic moment is $μ_a=-\frac{πf}{2α_s}$, where f is the packing fraction of instantons in the vacuum.
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.
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.
An analysis of electroweak corrections to the anomalous dipole moments of lepton from some special two-loop diagrams where a closed neutralino/chargino loop is inserted into relevant one-loop diagrams of the standard model is presented in the split supersymmetry scenarios. Considering the translational invariance of the inner loop momenta and the electromagnetic gauge invariance, we get all dimension 6 operators and their coefficients. After applying equations of motion to the external leptons, we obtain the anomalous dipole moments of lepton. The numerical results imply that there is paramete…
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}.
We have examined the anomalous electromagnetic moments of the tau lepton in the processes $e^{-}γ\to ν_eτ\barν_τ$ ($γ$ is the Compton backscattering photon) and $e^{-}e^{+} \to e^{-}γ^* e^{+} \to ν_{e}τ\barν_τe^+$ ($γ^*$ is the Weizsacker-Williams photon) with unpolarized and polarized electron beams at the CLIC. We have obtained 95$\%$ confidence level bounds on the anomalous magnetic and electric dipole moments for various values of the integrated luminosity and center-of-mass energy. Improved constraints of the anomalous magnetic and electric dipole moments have been obtained compared to th…
New data on the anomalous magnetic moment of the muon together with the b->s gamma decay rate and Higgs limits are considered within the supergravity inspired constrained minimal supersymmetric model. We perform a global statistical chi2 analysis of these data and show that the allowed region of parameter space is bounded from below by the Higgs limit, which depends on the trilinear coupling and from above by the 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.
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 $a_μ^{{\rm LBL},π^0} = +56 \times 10^{-11}$.
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.
The statistical limits on detectability of an anomalous chromomagnetic moment of a quark coupling to a gluon are projected to higher luminosities at the Tevatron at Fermilab, and to the LHC. They roughly scale as the energy, and are not strongly improved with increasing lumonisity.
The lepton flavor violating process μ \rightarrow eγ has been previously studied in a model of electroweak-scale right-handed neutrinos. We have calculated the decay amplitude in unitarity gauge [1] and Rξ gauge [2]. In this paper, we calculate the anomalous magnetic moment of μ in Rξ gauge.
