Andrzej Czarnecki, Matthew Dowling, Jorge Mondejar, Jan H. Piclum
备注：
6 pages, 3 figures, Talk presented at 10th DESY Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Wörlitz, Germany, 25-30 April 2010
Theoretical predictions underlying determinations of the fine structure constant alpha and the electron-to-proton mass ratio m_e/m_p are reviewed, with the emphasis on the bound electron magnetic anomaly g-2. The theory of the interaction of hydrogen-like ions with a magnetic field is discussed. The status of efforts aimed at the determination of O(alpha (Z alpha)^5) and O(alpha^2 (Z alpha)^5) corrections to the g factor is presented. The reevaluation of analogous corrections to the Lamb shift and the hyperfine splitting is summarized.
We compute the effective magnetic moment of neutrino in the highly dense and strongly magnetized media. It is shown that this magnetic moment is generated due to the effective mass of neutrino and gives sufficiently high value of the magnetic moment in the core of neutron stars.
I review the history on neutrino magnetic moments and apply the neurino magnetic moment idea to constrain its bound from Super-Kamiokande neutrino oscillation data.
We discuss the agreement in sign between the recently measured strange contribution to the proton magnetic moment and SU(3) based fits to baryon octet magnetic moments.
In chiral models with SU(3) group structure, baryon decuplet and octet magnetic moments are evaluated by constructing their sum rules to yield theoretical predictions. In these sum rules we exploit six experimentally known baryon magnetic moments. Sum rules for flavor components and strange form factors of the octet and decuplet magnetic moments and decuplet-to-octet transition magnetic moments are also investigated.
We study the magnetic moments and transition magnetic moments of $P_c$ and $P_{cs}$ states in the molecular picture. We first revisit the magnetic moments of $P_c$ states as the $S$ wave molecular states without coupled channel effects. The coupled channel effects and the $D$ wave contributions are then investigated carefully. The coupled channel effects contribute to the change of $0.1\sim 0.4$ nuclear magneton $μ_N$ for most cases while the $D$ wave only induces the variation of less than $0.03 ~μ_N$. In addition, we obtain the transition magnetic moments between different $P_c$ states and t…
Magnetic moments of the positive parity 70-plet baryons are estimated within the non relativistic quark model and QCD sum rules method. It is found that the magnetic moments of the 70-plet baryons can be expressed in terms of the D and F couplings and exhibit unitary symmetry. The QCD sum rules for the magnetic moments of the 70-plet octet baryons are formulated. Comparison of magnetic moments of 56-plet and 70-plet baryons predicted from QCD sum rules are presented.
New relations between QCD Borel sum rules for magnetic moments of Sigma^0 and Lambda hyperons are constructed. It is shown that starting from the sum rule for the Sigma^0 hyperon magnetic moment it is straightforward to obtain the corresponding sum rule for the Lambda hyperon magnetic moment et vice versa.
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.
We discuss magnetic moments of the $J=3/2$ baryons based on an earlier model for the baryon magnetic moments, allowing for flavor symmetry breaking in the quark magnetic moments as well as a general quark spin structure. From our earlier analysis of the nucleon-hyperon magnetic moments and the measured values of the magnetic moments of $Δ^{++}$ and $Ω^{-}$ we predict the other magnetic moments and deduce the spin structure of the resonance particles. We find from experiment that the total spin polarization of the decuplet baryons, $ΔΣ(3/2)$, is considerably smaller than the non-relativistic qu…
The existence of magnetic moments of neutrinos points to physics beyond the standard model. Given current upper limits, terrestrial measurements are difficult or completely unfeasible. However, estimates of transition moments can be obtained from observation of objects such as active galactic nuclei (AGN) by means of neutrino telescopes. We describe the way of estimating the magnitudes of transition moments from such observations.
We study the neutrino-photon processes like $γγ\toν\barν$ in the presence of uniform external magnetic field for the case when neutrinos can couple to the electromagnetic field directly through their dipole magnetic moment and obtain the stellar energy loss. The process would be of special relevance in astrophysical situations where standard left-handed neutrinos are trapped and the right handed neutrinos produced through the spin flip interaction induced by neutrino magnetic moment alone can freely stream out.
Magnetic quadrupole moment of $W$-boson in Kobayashi-Maskawa model, I.B. Khriplovich and M.E. Pospelov, BUDKERINP 93--88 Due to CP-invariance violation a vector particle can acquire T- and P-odd electromagnetic moment, magnetic quadrupole one. The W-boson magnetic quadrupole moment is calculated in the Kobayashi-Maskawa model. This is the only known CP-odd moment arising in this model in two-loop approximation.
We show that there is an anologous Aharonov-Casher effect on a neutral particle with electric dipole moment interacting with a magnetic filed produced by magnetic monopoles.
We express the baryon magnetic moments in terms of the baryon tensor charges, considering the quarks as relativistic interacting objects. Once tensor charges get measured accurately, the formula for the baryon magnetic moment will serve to extract precise information on the quark anomalous magnetic moment, the quark effective mass and the ratio of the quark constituent mass to the quark effective mass. The analogous formula for the baryon electric dipole moment is of no great use as it gets eventually sizable contributions from various CP- violating sources not necessary associated to the quar…
The magnetic moments of heavy sextet $J^P = {1\over 2}^+$ baryons are calculated in framework of the light cone QCD sum rules method. Linearly independent relations among the magnetic moments of these baryons are obtained. The results for the magnetic moments of heavy baryons obtained in this work are compared with the predictions of the other approaches.
The $Ξ_Q^\prime$-$Ξ_Q$ transition magnetic moments are calculated in framework of the light cone QCD sum rules method (LCSR). The values of the transition magnetic moments obtained are compared with the predictions of the other theoretical approaches.
It is shown that the difference between the magnetic moment results in the quark model with null instantons and semibosonized Nambu-Jona-Lasinio model lies in the description of the magnetic moment of the $ Λ$-hyperon.
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 …
We analyze different observables to study the magnetic dipole moment of the tau pairs produced by photon linear colliders. We use the circular polarized photon beam and study distributions of polarized $τ$ final pairs to define sensibly asymmetries to magnetic dipole moment.
We recalculate the magnetic moment of neutrinos in a hot and dense medium. The magnetic dipole moment of neutrinos is modified at high temperature and chemical potential. We show that the magnetic dipole moment of electron neutrino does not get a significant contribution from thermal background to meet the cosmological bound. However, chemical potential contribution to the magnetic moment is non-ignorable even when chemical potential is an order of magnitude greater than the electron mass. It is demonstrated that this effect is more significant in the models with an extended Higgs sector throu…
The effective Lagrangian approach allows us to constrain fermion magnetic and electric moments using LEP-I data. We improve some of the previous limits on these moments.
It is shown that the baryon magnetic moment descriptions in the frameworks of the chiral model ChPT and the quark soliton $χQSM $ one are practically identical. The main difference from the traditional unitary symmetry models proves to be in terms due to the pionic current contribution into the magnetic moments of nucleons and in the prediction for the $Λ$ magnetic moment.
We calculate the magnetic moments of Delta baryons within the framework of QCD sum rules. A comparison of our results on the magnetic moments of the Delta baryons with the predictions of different approaches is presented.
Using the colored quark cluster model, we study magnetic moments of the octet baryons. We give the values of the magnetic moments of baryons $p$, $n$, $Σ^+$, $Σ^-$, $Ξ^0$, and $Ξ^-$. The results also show that the orbital motion has very significant effects on the spin and magnetic moments of those baryons and the strange component in the proton is very small.
We perform the calculation of the nucleon dipole magnetic moment in full detail using the Gordon decomposition of the free quark current. This calculation has become necessary because of frequent misuse of the Gordon decomposition by some authors in computing the nucleon dipole magnetic moment.
Current experimental and observational limits on the neutrino magnetic moment are reviewed. Implications of the recent results from the solar and reactor neutrino experiments for the value of the neutrino magnetic moment are discussed. It is shown that spin-flavor precession in the Sun is suppressed.
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 calculate the magnetic moments of decuplet baryons containing strange quarks within the framework of light cone QCD sum rules taking into account the SU(3) flavor symmetry breaking effects. It is obtained that magnetic moments of the neutral $\sso$ and $\xis0$ baryons are mainly determined by the SU(3) breaking terms. A comparison of our results on the magnetic moments of the decuplet baryons with the predictions of other approaches is presented.
We show that the magnetic moment of leptons is significantly modified in thermal background as compared to the corresponding vacuum value. We compare the magnetic moment of all different leptons near nucleosynthesis. It is shown that the significance of thermal corrections depends on the temperature of the universe and the respective lepton mass. In the early universe, particle mass was growing quadratically with temperature which affects the corresponding value of magnetic moment. Intrinsic magnetic moment is inversely proportional to mass whereas thermal corrections to the neutrino dipole mo…
The method of QCD sum rules in the presence of external elctromagnetic fields is used to calculate the $Ω$ magnetic moment $μ_{Ω^-}$ and $Σ^0$-$Λ$ transition magnetic moment $μ_{Σ^0Λ}$, with the susceptibilities obtained previously from the study of octet baryon magnetic moments. The results $μ_{Ω^-}=-1.92μ_N$ and $μ_{Σ^0Λ}=1.5μ_N$ are in good agreement with the recent experimental data.
The magnetic moments of the baryon decuplet are calculated in a relativistic constituent quark model using the light-front formalism. Of particular interest are the magnetic moments of the $Ω^-$ and $Δ^{++}$ for which new recent experimental measurements are available. Our calculation for the magnetic moment ratio $μ(Δ^{++})/μ(p)$ is in excellent agreement with the experimental ratio, while our ratio $μ(Ω^-)/μ(Λ^0)$ is slightly higher than the experimental ratio.
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.
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.
The magnetic moment $μ$ of the "rho" meson is studied in QCD light cone sum rules, and it is found that "mu = (2.3 pm 0.5)". A comparison of our result on the magnetic moment of the "rho" meson with the predictions of the other approaches, is presented.
A model independent, field theoretical relation between baryon magnetic moment and its spin structure is derived and it is explained why constituent quark model is a good approximation in describing baryon magnetic moments.
This paper calculates the magnetic moments of the hidden-charm strange pentaquark states with a quantum number of $J^P={\frac{1}{2}}^{\pm}$, ${\frac{3}{2}}^{\pm}$, ${\frac{5}{2}}^{\pm}$, and ${\frac{7}{2}}^{+}$ in the molecular, diquark-diquark-antiquark, and diquark-triquark models, respectively. Numerical results demonstrate that the magnetic moments change for a different spin-orbit coupling with the same model and when involving different models with the same angular momentum.
We present calculations of the decuplet baryon magnetic moments in the chiral quark model. As input we use parameters obtained in qualitatively accurate fits to the octet baryon magnetic moments studied previously. The values found for the magnetic moments of $Δ^{++}$ and $Ω^{-}$ are in good agreement with experiments. We finally calculate the total quark spin polarizations of the decuplet baryons and find that they are considerably smaller than what is expected from the non-relativistic quark model.
In this article, we study the magnetic moment of the pentaquark state $ Θ^+(1540)$ with the QCD sum rules approach in the external electromagnetic field. The numerical results indicate the magnetic moment of the pentaquark state $ Θ^+(1540)$ is about $μ_{Θ^+}=(0.24\pm0.02)μ_N$.
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.
Due to the very short life time of the $Δ$ baryons, a direct measurement on the electromagnetic moments of these systems is almost impossible in the experiment and can only be done indirectly. Although only for the magnetic dipole moments of $Δ^{++}$ and $Δ^{+}$ systems there are some experimental data, the theoretical, phenomenological and lattice calculations could play crucial role. In present work, the magnetic dipole ($μ_Δ$) , electric quadrupole ($Q_Δ$) and magnetic octupole ($O_Δ$) moments of these baryons are computed within the light cone QCD sum rules. The results are compared with t…
We discuss neutrino magnetic moments as a way of constraining physics beyond the Standard Model. In fact, new physics at the TeV scale can easily generate observable neutrino magnetic moments, and there exists a multitude of ways of probing them. We highlight in particular direct dark matter detection experiments (which are sensitive to neutrino magnetic moments because of the predicted modifications to the solar neutrino scattering rate), stellar cooling, and cosmological constraints.
The electromagnetic properties of the tetraquark state $Z_c(3900)$ are investigated in the diquark-antidiquark picture and its magnetic and quadrupole moments are extracted. To this end, the light-cone QCD sum rule in electromagnetic background field is used. The magnetic and quadrupole moments encode the spatial distributions of the charge and magnetization in the particle. The result obtained for the magnetic moment is quite large and can be measured in future experiments. We obtain a nonzero but small value for the quadrupole moment of $Zc(3900)$ indicating a nonspherical charge distributio…
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.
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 …
Using the Ritus eingenfunction method we compute corrections to the electron mass m_{0} in the presence of a moderate magnetic field eB ~ m_0^2. From this we obtain an expression for the anomalous magnetic moment near the critic field. For this we solved numerically the Schwinger-Dyson equations in the rainbow approximation including all Landau levels without make any assumption respect to the field strength.
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.
Solar neutrinos with non-zero magnetic moments will contribute to the electron scattering rates in the Super-Kamiokande experiment. The magnetic moment scattering events in Super-K can be accommodated in the standard VO or MSW solutions by a change of the parameter space of mass square difference and mixing angle-but the shifted neutrino parameters obtained from Super-K will (for some values of neutrino magnetic moments) become incompatible with the fits from SNO, Gallium and Chlorine experiments. We compute the upper bounds on the Dirac and Majorana magnetic moments of solar neutrinos by simu…
Recent Standard Model predictions for the anomalous magnetic moments of the electron, muon and tau lepton are reviewed and compared to the latest experimental values.
The importance of exchange currents, and of conserving isotopic spin at both the quark and baryon levels in application of the chiral quark model to any calculation of baryon magnetic moments is emphasized.
We investigate the leading order correction of anomalous magnetic moment (AMM) to the electron in 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 $\mathrm{T}$, 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 current measurement. However, when the magnitude of the magnetic field str…
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.
