Soft gluon fields and anomalous magnetic moment of muon

An impact of nonperturbatively treated soft gluon modes on the value of anomalous magnetic moment of muon a_µ is studied within the mean-field approach to QCD vacuum and hadronization. It is shown that radial excitations of vector mesons strongly enhance contribution of hadronic vacuum polarization to a_µ, doubling the contribution of one-meson processes compared to the result for ground state mesons. The mean field also strongly influences the hadronic light-by-light scattering contribution due to the Wilson line in quark propagators.

Highly Accurate Derivation of the Electron Magnetic Moment Anomaly From Spherical Geometry Using a Single Evaluation

The electron magnetic moment anomaly (ae), is normally derived from the fine structure constant using an intricate method requiring over 13,500 evaluations, which is accurate to 11dp. This paper advances the derivation using the fine structure constant and a spherical geometric model for the charge of the electron to reformulate the equation for ae. This highly accurate derivation is also based on the natural log eπ, and the zero-order spherical Bessel function. This determines a value for the electron magnetic moment anomaly accurate to 13 decimal places, which gives a result which is 2 orders of magnitude greater in accuracy than the conventional derivation. Thus, this derivation supersedes the accuracy of the conventional derivation using only a single evaluation.

Longitudinal remagnetization of uniaxial antiferromagnetic nanoparticles: the role of spontaneous magnetic moment

A kinetic theory of magnetic response of uniaxial antiferromagnetic nanoparticles is presented. Within the developed framework, a particular case when an external field is applied strictly along the anisotropy axis is considered in detail. Analysis of the relaxation spectrum of an antiferromagnetic particle with a spontaneous magnetic moment is performed. It is shown that in a wide frequency range the magnetic response of such particle is determined entirely by the relaxation mode with the longest time. An analytical expression for this time that explicitly contains a value of the decompensation magnetic moment is derived. Also, simple formulae for both static and dynamic longitudinal magnetic susceptibility of an antiferromagnetic nanoparticle are obtained. According to them, longitudinal susceptibility grows quadratically with the value of the spontaneous magnetic moment. Besides, if the latter is not zero, the change of the static susceptibility with temperature turns out to be non-monotonic. The influence of the spontaneous magnetic moment of the particle on the magnetization curves in strong fields is analysed using both energy approach and kinetic theory. The calculated dependences of the dynamic coercivity on the amplitude and variation rate of the applied field are qualitatively compared with experimental data. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

Data-driven approaches to the evaluation of hadronic contributions to the (g − 2)μ

In this talk I reviewed the data-driven theoretical calculation of the hadronic contributions to the anomalous magnetic moment of the muon in the Standard Model mainly as it has been presented in the White Paper, but also including the most recent developments. All this is presented in the light of the new measurement of (g − 2)μ recently released by the Fermilab experiment, which led to an increase of the discrepancy with the Standard Model from 3.7 to 4.2σ.

Toroidal versus centripetal arrangement of magnetic moment in a Dy4 tetrahedron

Magnetic investigation and ab initio calculations reveal toroidal arrangement of the magnetic moment rather than centripetal anisotropies in a tetrahedral Dy4 complex.