相关论文: Remarkable suppression of the $e^{+}e^{-}\to\pi^{+…
We complement studies of the neutral pion transition form factor pi^0 --> gamma^(*) gamma^(*) with calculations for the electromagnetic decay widths of the processes pi^0 --> e^+ e^-, pi^0 --> e^+ e^- gamma and pi^0 --> e^+ e^- e^+ e^-.…
We study the pion electromagnetic form factor in the modulus squared dispersion relation, and do the model independent extraction of the most important nonperturbative parameters in pion light-cone distribution amplitude. The motivation of…
The hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu}^{\rm had, VP}$ have been re-evaluated from the combination of $e^+e^-\rightarrow {\rm hadrons}$ cross section data. Focus has been placed…
The recently proposed MUonE experiment at CERN aims at providing a novel determination of the leading order hadronic contribution to the muon anomalous magnetic moment through the study of elastic muon-electron scattering at relatively…
A precise evaluation of the electroweak contribution to the anomalous magnetic moment of the muon requires control over all aspects of the Standard Model, ranging from Higgs physics, over multi-loop computations for bosonic and…
This article reviews the muon g-2 experiment, a cornerstone in precision tests of the Standard Model of particle physics. The experiment measures the anomalous magnetic moment of the muon with unprecedented accuracy, seeking potential…
Standard Model contributions to the electron, muon, and tau lepton anomalous magnetic moments, a_l=(g_l-2)/2, are reviewed and updated. The fine structure constant is obtained from the electron g_e-2 and used to refine the QED contribution…
We present a model based on the implication of an exceptional E_{6}-GUT symmetry for the anomalous magnetic moment of the muon. We follow a particular chain of breakings with Higgses in the 78 and 351 representations. We analyse the…
The result of lowest-order perturbation theory calculations of the photon and positron spectra in radiative pion(e2) decay are generalized to all orders of perturbation theory using the structure-function method. An additional source of…
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…
The stringent experimental bound on $\mu \rightarrow e \gamma$ is compatible with a simultaneous and sizable new physics contribution to the electron and muon anomalous magnetic moments $(g-2)_\ell$ ($\ell=e,\,\mu$), only if we assume a…
Recent calculations of the hadronic vacuum polarisation contribution are reviewed. The focus is put on the leading-order contribution to the muon magnetic anomaly involving $e^+e^-$ annihilation cross section data as input to a dispersion…
The process of $e^+e^-$ annihilation into a $\pi^+\pi^-$ pair with radiation of a photon is considered. The amplitude of the reaction $e^+e^-\to\pi^+\pi^-\gamma$ consists of the model independent initial-state radiation (ISR) and…
Soon, new experiments at FNAL and J-PARC will measure the muon anomalous magnetic moments with better accuracy than before. From theoretical side, the uncertainty of the standard model prediction is dominated by the hadronic contributions.…
We show that the $J/\psi \rightarrow \pi^{+} \pi^{-}$ decay is a reliable source of information for the electromagnetic form factor of the pion at $t=M_{J/\psi}^2=9.6 {\rm GeV}^2$ by using general arguments to estimate, or rather, put upper…
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…
The anomalous magnetic moment of the muon displays a $4.2\sigma$ tension with the Standard-Model prediction, if $e^+e^-\to \text{hadrons}$ data are used for hadronic vacuum polarization. In these proceedings we review possible explanations…
In this talk I review the recent progress on the numerical evaluation of the Hadronic Light-by-Light contribution to the anomalous magnetic moment of the muon and I discuss the role of experimental data on the accuracy of its determination.
The KLOE Experiment at the $\phi$ factory DA$\Phi$NE, has measured the cross section $\sigma(e^+e^-\to\pi^+\pi^-\gamma)$ using two different selection schemes: requiring the photon emission at small polar angle and detecting the photon at…
In 2008 the Jefferson Laboratory $F_\pi$ Collaboration released results for the pion electromagnetic form factor, which they extracted from pion electro-production data. The measured values for the pion form factor are model dependent, and…