Related papers: On some implications of the BaBar data on the $\ga…
The $\eta$ transition form factor is analysed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The $\eta\rightarrow…
We derive the light-front wave function (LFWF) representation of the $\gamma^* \gamma^* \to \eta_c(1S)\,,\eta_c(2S)$ transition form factor $F(Q_1^2, Q_2^2)$ for two virtual photons in the initial state. For the LFWF, we use different…
The $\gamma \gamma^\ast \to \eta_{c,b}$ transition form factors are computed using a continuum approach to the two valence-body bound-state problem in relativistic quantum field theory, and thereby unified with equivalent calculations of…
An analysis of all available data (CELLO, CLEO, \babar) in the range $[1\div 40]$ GeV$^2$ for the pion-photon transition form factor in terms of light-cone sum rules with next-to-leading-order accuracy is discussed, including twist-four…
We compute power-suppressed corrections to the \eta\gamma and \eta^{\prime}\gamma transition form factors Q^2F_{\eta(\eta^{\prime})\gamma}(Q^2) arising from the end point regions x \to 0,1 by employing the infrared-renormalon approach. The…
We present measurements of the gamma gamma* --> pi0 transition form factor for the momentum transfer range Q^2=4-40 GeV^2 and the gamma gamma* --> eta_c transition form factor for the range Q^2=2-50 GeV^2. The results of the measurement of…
A dispersion integral is derived that connects data on $\eta\to \pi^+\pi^-\gamma$ to the $\eta\to \gamma\gamma^*$ transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the $\eta$ transition…
We present the results of our recent analysis of the meson-photon transition form factors $F_{P\gamma}(Q^2)$ for the pseudoscalar mesons $P = \pi^0,\eta,\eta',\eta_c$, using the local-duality version of QCD sum rules.
We study the reactions e+e- --> e+e- eta (eta') in the single-tag mode and measure the gamma gamma* --> eta (eta') transition form factors in the momentum transfer range from 4 to 40 GeV^2. The analysis is based on 469 fb-1 of integrated…
Starting from the axial vector Ward-Green-Takahashi identity, and the necessity of preserving this identity when attempting to calculate the properties describing pseudoscalar mesons, we describe a Bethe-Salpeter kernel which takes into…
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 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 reanalyze the eta-gamma and eta'-gamma transition form factors within the modified hard scattering approach on the basis of new experimental data from CLEO and L3. Our approach perfectly describes the experimental data over a wide range…
The light-front quark model analysis of the meson-photon transition form factor $F_{P\gamma} (Q^2)$ amenable both for the spacelike region ($Q^2 >0$) and the timelike region ($Q^2 <0$) provides a systematic twist expansion of $Q^2…
We study the $\eta'-g^*-g$ transition form factor by using the $\eta'$ wave function constrained by the experimental data on the $\eta'-\gamma^*-\gamma$ transition form factor provided by CLEO and L3 . We also take into account the…
For the spacelike momenta k of the virtual photon gamma^*, the pi^0(p) gamma^*(k) gamma(k') transition form factor is considered in the coupled Schwinger-Dyson and Bethe-Salpeter approach in conjunction with the generalized impulse…
The surprising results by the BarBar collaboration on the $\pi\gamma$ transition form factor require new thoughts about the high-$Q^2$ dependence of the form factors with virtual photons. We make use of the anomaly sum rule [J. Horejsi and…
The \eta and \eta' transition form factors in the space-like region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as…
We study photon-meson transition formfactors of light mesons in the kinematics, where one photon is real and other is virtual. Dispersive approach to axial anomaly leads to the anomaly sum rule. The absence of corrections to it allows us to…
We study the $\gamma^* \gamma^*\to\eta_c$ transition form factor, $F_{\eta_c\gamma\gamma}(Q_1^2,Q_2^2),$ with the local-duality (LD) version of QCD sum rules. We analyse the extraction of this quantity from two different correlators,…