Related papers: Lightest pseudoscalar exchange contribution to lig…
The photon-meson transition form factors of light pseudoscalar mesons $\pi ^{0}$, $\eta$, and $\eta ^{\prime}$ are systematically calculated in a light-cone framework, which is applicable as a light-cone quark model at low $Q^{2}$ and is…
We present a dispersive representation of the $\eta'$ transition form factor that allows one to account, in a consistent way, for the effects of $\rho$-$\omega$ mixing in both the isoscalar and the isovector contributions. Using this…
We consider implications of the diphoton excess recently observed at the LHC on the anomalous magnetic dipole moment of the muon $(g-2)_\mu = 2 a_\mu$, hypothesizing that the possible 750 GeV resonance is a (pseudo)scalar particle. The…
The hadronic light-by-light scattering contribution to the muon anomalous magnetic moment, $(g-2$)/2, is computed in the infinite volume QED framework with lattice QCD. We report $a_\mu^\text{HLbL}=12.47(1.15)(0.95) \times 10^{-10}$ where…
We present results for single axial-vector and scalar meson pole contributions to the hadronic light-by-light scattering (HLbL) part of the muon's anomalous magnetic moment. In the dispersive approach to these quantities (in narrow width…
In this work we study the axial contributions to the hadronic light-by-light piece of the muon anomalous magnetic moment using the framework of resonance chiral theory. As a result, we obtain $a_{\mu}^{\textrm{HLbL};A} =…
In the framework of Chiral Perturbation Theory including photons, we found that the contribution of the photon exchange between two intermediate charged Kaons to the slope parameter of the decay (\eta\rightarrow 3\pi^{0}) amounts to…
We discuss the role of meson exchange mechanisms in $\gamma \gamma \to \gamma \gamma$ scattering. Several pseudoscalar ($\pi^0$, $\eta$, $\eta'(958)$, $\eta_c(1S)$, $\eta_c(2S)$), scalar ($f_{0}(500)$, $f_0(980)$, $a_0(980)$, $f_0(1370)$,…
In this work, we present an evaluation of subleading effects in the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Using a recently derived optimized basis, we first study the matching of axial-vector…
The electromagnetic structure of axial-vector mesons is investigated via elastic and two-photon transition form factors (TFFs). To this end, we employ a framework based on the Dyson-Schwinger and Bethe-Salpeter equations within a contact…
We evaluate the contribution of scalar mesons to the hadronic light-by-light piece of the muon anomalous magnetic moment, using a warped five-dimensional model and holographic methods. We assess the contribution of the lightest, sub-GeV…
The rare decays $\eta^{(\prime)}\to\ell^+\ell^-$, $\ell\in\{e,\mu\}$, are highly suppressed in the Standard Model, both by their chirality structure and the required loop attaching the lepton line to the $\eta^{(\prime)}\to\gamma^*\gamma^*$…
We compute the light axial-vector and tensor meson two-photon transition form factors in the soft-wall holographic model of QCD in the flavor-symmetric case. They are used to evaluate the axial-vector and tensor meson contributions to the…
Measuring the lepton anomalous magnetic moments $(g-2)$ and the rare decays of light pseudoscalar mesons into lepton pairs $P\to l^{+}l^{-} $, serve as important tests of the Standard Model. To reduce the theoretical uncertainty in the…
We discuss a realization of the non-abelian group O(2) as a family symmetry for the lepton sector. The reflection contained in O(2) acts as a mu-tau interchange symmetry, enforcing--at tree level--maximal atmospheric neutrino mixing and a…
This talk discusses our old work on the hadronic light-by-light contribution to the muon anomalous magnetic moment and some more recent contributions. I discuss the various contributions starting with pseudo-scalar meson exchange, the…
We calculate the $\pi^0\to \gamma^*\gamma^*$ transition form factor ${\cal F}_{\pi^0\gamma^*\gamma^*}(q_1^2,q_2^2)$ in lattice QCD with two flavors of quarks. Our main motivation is to provide the input to calculate the $\pi^0$-pole…
We consider an impact of hadronic light-by-light scattering on the muonium hyperfine structure. A shift of the hyperfine interval $\Delta \nu({\rm Mu}) _{\rm\tiny HLBL}$ is calculated with the light-by-light scattering approximated by…
A dispersive implementation of the $a_0(980)$ resonance to $(g-2)_\mu$ requires the knowledge of the double-virtual $S$-wave $\gamma^*\gamma^*\to\pi\eta / K\bar{K}_{I=1}$ amplitudes. To obtain these amplitudes we used a modified…
The hadronic light-by-light scattering contribution to muon $g-2$ is examined using low energy effective theories of QCD, the Nambu-Jona-Lasinio model and hidden local chiral symmetry, as guides. Our result is $- 36 \times 10^{-11}$ with an…