Related papers: Form factor $\pi^0\to \gamma^* +\gamma^*$ at diffe…
Pion transition form factor for the process $\gamma*\gamma*\to \pi^0$ at space-like values of photon momenta is calculated within the effective quark-meson model with the interaction induced by instanton exchange. The leading and…
In the presence of a momentum cutoff, effective theories seem unable to faithfully reproduce the so called chiral anomaly in the Standard Model. A novel prospect to overcome this related issue is discussed herein via the calculation of the…
We perform a comprehensive analysis of the pion-photon transition form factor $F_{\pi \gamma}(Q^2)$ involving the transverse momentum corrections with the present CLEO experimental data, in which the contributions beyond the leading Fock…
We analyze $F_\pi(Q^2)$ and $F_{P\gamma}(Q^2)$, $P=\pi,\eta,\eta'$, within the local-duality (LD) version of QCD sum rules, which allows one to obtain predictions for hadron form factors in a broad range of momentum transfers. To probe the…
We provide a theoretical update of the calculations of the pi0-gamma*-gamma form factor in the LCSR framework, including up to six polynomials in the conformal expansion of the pion distribution amplitude and taking into account twist-six…
I present the calculation of the $\pi^+\gamma^\star\to\pi^+\pi^0$ transition amplitude from quantum chromodynamics performed by the Hadron Spectrum Collaboration. The amplitude is determined for a range of values of the photon virtuality…
We study the pion form factor F^{\pi \gamma\gamma^*}(Q^2) in the light-cone sum rule approach, accounting for radiative corrections and higher twist effects. Comparing the results to the CLEO experimental data on F^{\pi…
We calculate the contributions from QED processes involving two virtual photons to the cross sections for e^+ e^- annihilation into two charmonium states with the same C-parity. Generically, the cross sections are three orders of magnitude…
The method of calculating electroweak decay matrix elements between heavy-heavy and heavy-light meson states is developed in the framework of relativistic quark model based on the quasipotential approach in quantum field theory. This method…
The form factor for gamma pi^+ -> pi^+ pi^0 was calculated in a simple-minded constituent model with a constant quark mass parameter, as well as in the Schwinger-Dyson approach. The comparative discussion of these and various other…
Recently, the BABAR collaboration published (arXiv:0905.4778) data for the photon-pion transition form factor $F_{\pi\gamma\gamma^{\ast}}(Q^{2})$, which are in strong contradiction to the predictions of the standard factorization approach…
We consider a model of dark quantum electrodynamics which is coupled with a visible photon through a kinetic mixing term. After checking of consistency properties, we compute the $g_w-2$, where $g_w$ is the gyromagnetic factor for a dark…
The two-dimensional one-component plasma is an ubiquitous model for several vortex systems. For special values of the coupling constant $\beta q^2$ (where $q$ is the particles charge and $\beta$ the inverse temperature), the model also…
The nucleon spin-averaged forward virtual Compton tensor determines important physical quantities such as electromagnetically-induced mass differences of nucleons, and two-photon exchange contributions in hydrogen spectroscopy. It depends…
We present complete results for the $O(\alpha_s)$ corrections to the production of a heavy quark pair plus a hard photon, in $e^+ e^-$ annihilation, including both photon and $Z$ intermediate states. Virtual corrections are calculated…
The ladder Bethe-Salpeter solution for the dressed photon-quark vertex is used to study the low-momentum behavior of the pion electromagnetic and the $\gamma^\star \pi^0 \gamma$ transition form factors. With model parameters previously…
The calculation of electroweak corrections to processes with jets in the final state involves contributions of low-virtuality photons leading to jets in the final state via the singular splitting $\gamma^* \to q\bar q$. These singularities…
In this article, we calculate the vector form factors $f^+_{K\pi}(Q^2)$ and $f^-_{K\pi}(Q^2)$ within the framework of the light-cone QCD sum rules approach. The numerical values of the $f^+_{K\pi}(Q^2)$ are compatible with the existing…
The structure of both quasi-real and highly virtual photons is investigated using the reaction e+e- -> e+e-mu+mu-, proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at e+e- centre-of-mass…
In present note the arguments in favour of future high statistical measurements of the formfactors that describe pi-meson decays into lepton-antilepton pair and photon are presented. It is shown that these formfactors Q^2 dependence…