Search results for "Anomalous magnetic dipole moment"
showing 10 items of 91 documents
Study of the anomalous magnetic moment of the muon computed from the Adler function
2014
We compute the Adler function on the lattice from vacuum polarization data with twisted boundary conditions using numerical derivatives. The study is based on CLS ensembles with two flavours of $O(a)$ improved Wilson fermions. We extrapolate the lattice data for the Adler function to the continuum limit and to the physical pion mass and analyze its dependence on the momentum transfer. We discuss the application of this method to the extraction of the $u,d$ contribution to $a_\mu^{\mathrm{HLO}}$.
The muon magnetic moment
1981
Muon mass and muon magnetic moment are not calculabIe within the theory of Quantum Eiectrodynamics; they rather define the reference acaie in which masses and energies should be determined when muons are used to test QED or to search for anomalous muon coupiings which couid provide the "raison d'@tre" for the muon. Oniy the anomaious part of the muon magnetic moment experimentaily determined with remarkable precision I), can be oaIculated 2~" Theory and experiment agree preciseiy once corrections being appiied for hadronic and weak processes which poiiute the immaculated fieid of QED at high momentum transfers. Muon mass and muon magnetic moment are, in particular, needed for the interpreta…
The Drell-Hearn-Gerasimov Sum Rule
1994
The Drell-Hearn-Gerasimov (DHG) sum rule relates the helicity structure of the photoabsorption cross section to the anomalous magnetic moment of the nucleon. It is based on Lorentz and gauge invariance, crossing symmetry, causality and unitarity. A generalized DHG sum rule my be derived for virtual photons. At low momentum transfer this generalized sum rule is saturated by the resonance region, at high momentum transfer it may be expressed by the parton spin distributions measured in deep inelastic scattering. The longitudinal-transverse interference determines the Cottingham sum rule, which is related to the electric and magnetic form factors over the whole range of momentum transfer.
Towards electronic g-factor measurements in medium-heavy hydrogen-like and lithium-like ions
2005
Abstract Measurements of the anomalous magnetic moment of the electron bound in hydrogen-like ions with spinless nuclei have proven to be highly sensitive tests of corresponding calculations based on bound-state quantum electrodynamics. Measurements performed on H-like carbon 12C5+ and oxygen 16O7+ together with bound-state QED calculations on the same level of accuracy have achieved sensitivities around 0.25% of the QED bound state contributions to the calculated electronic g-factors of these ions. Currently, a similar experiment on hydrogen-like calcium 40Ca19+, lithium-like calcium 40Ca17+ and other medium-heavy ions is being prepared, which is capable of increasing this sensitivity on t…
The hadronic light-by-light contribution to the muon's anomalous magnetic moment
2019
In view of the current 3 - 4 $\sigma$ deviation between theoretical and experimental values for the muon's anomalous magnetic moment, we review the ongoing efforts in constraining the hadronic light-by-light contribution to $a_\mu$ by using dispersive techniques combined with a dedicated experimental program to obtain the required hadronic input.
The generalized Gerasimov–Drell–Hearn sum rule for deuteron electrodisintegration
2004
The generalized Gerasimov-Drell-Hearn sum rule $I^{GDH}_{\gamma^*d}(Q^2)$ for deuteron electrodisintegration $d(e,e')np$ as function of the squared four-momentum transfer $Q^2$ is evaluated by explicit integration. The calculation is based on a conventional nonrelativistic framework using a realistic $NN$-potential and including contributions from meson exchange currents, isobar configurations and leading order relativistic terms. Good convergence is achieved. The prominent feature is a deep negative minimum, $I_{\gamma^* d}^{GDH}=-9.5$ mb, at low $Q^2\approx 0.2$ fm$^{-2}$ which is almost exclusively driven by the nucleon isovector anomalous magnetic moment contribution to the magnetic dip…
General flavor blind minimal supersymmetric standard model andCPviolation
2001
We study the implications on flavor changing neutral current and $\mathrm{CP}$ violating processes in the context of supersymmetric theories without a new flavor structure (flavor blind supersymmetry). The low-energy parameters are determined by the running of the soft breaking terms from the grand unified scale with supersymmetric (SUSY) phases consistent with the electric dipole moment constraints. We find that the $\mathrm{CP}$ asymmetry in $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma}$ can reach large values potentially measurable at B factories, especially in the low $BR(\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma})$ region, while the contributions to electr…
Hadronic contribution to the lepton anomalous magnetic moment and pion form factor in lattice QCD
2012
Abstract The Mainz lattice QCD group is currently carrying out simulations of lattice QCD with the aim of making predictions for a wide range of phenomenologically relevant Standard Model properties. Here we present progress in understanding and controlling systematic effects in the computation of the pion vector form factor and the leading hadronic contribution to the lepton anomalous magnetic moment.
Tau spin correlations and the anomalous magnetic moment
2009
We show that the precise determination of the Tau magnetic properties is possible in the next generation accelerators, specially at B/Flavour factories. We define spin correlation observables suitable to extract the real part of the magnetic form factor that, for the first time, will allow to test the standard model-QED predictions. In particular, the predicted QED-dependence with both the momentum transfer and the lepton mass can be precisely measured. Until now, the most stringent bounds on the $\tau$ magnetic moment $a_\tau$ come from LEP data with strong assumptions on the physics involved on the observed process. In this paper, we find three different combinations of spin correlations …
Vector form factor of the pion from unitarity and analyticity: a model-independent approach
2001
7 páginas, 2 figuras, 3 tablas.-- PACS number(s): 13.35.Dx, 12.39.Fe, 13.40.Gp, 13.65.1i