Related papers: A perturbative approach to the eta_c-gamma transit…
The eta_c-gamma transition form factor is calculated in a model based on a modified hard scattering approach to exclusive reactions, in which transverse degrees of freedom are taken into account. For the eta_c-meson a distribution amplitude…
The eta(c)-gamma transition form factor is calculated within a perturbative approach. It is shown that the Q^2 dependence of the form factor is well determined in the region where experimental data is expected in the near future.
The Dalitz distribution and the effective mass spectrum of the lepton pair produced in the decay $\eta_c\to \gamma \ell^+ \ell^-$, as well as the differential cross sections for the crossed channels $\gamma e^-\to \eta_c e^- $ and $e^+…
We study the form factors of the $\eta_c$ meson in the light-front quark model. We explicitly show that the transition form factor of $\eta_c \to \gamma^* \gamma$ as a function of the momentum transfer is consistent with the experimental…
The form factors for the transitions pi-photon, eta-photon, eta'-photon and etac-photon are analyzed within the modified perturbative approach in which quark transverse degrees of freedom are retained. The results for the form factors are…
The two photon transition of $\bar{c}c$ quarkonia are studied within a covariant approach based on the consistent truncation scheme of the quantum chromodynamics Dyson-Schwinger equation for the quark propagator and the Bethe--Salpeter…
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…
We present a calculation of $P\to \gamma^{(\ast)}\gamma^{(\ast)}$ processes, where $P=\pi^0,\ \eta,\ \eta'$, at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-$N_c$ chiral perturbation theory. The…
The eta-gamma and eta'-gamma transition form factors are analyzed to leading-twist accuracy and next-to-leading order (NLO) of perturbative QCD. Using an eta-eta' mixing scheme and all currently available experimental data the lowest…
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…
We report results on the $\pi$-$\gamma$ transition form factor obtained within the hard scattering approach including transverse momentum effects and Sudakov corrections. The results clearly favor distribution amplitudes close to the…
We discuss $(\pi^0,\eta,\eta')\to\gamma^*\gamma$ transition form factors using the light-front quark model. Our discussion includes the analysis of the mixing angles for $\eta-\eta'$. Our results for $Q^2…
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 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 update the theoretical framework for the QCD calculation of transition form factors $\gamma^*\gamma\to\eta$ and $\gamma^*\gamma\to\eta'$ at large photon virtualities including full next-to-leading order analysis of perturbative…
The applications of the consistently coupled Schwinger-Dyson and Bethe-Salpeter approach to the eta-eta' complex are extended to the two-photon transition form factors of eta and eta' for spacelike transferred momenta. We compare our…
It is reported on predictions for the $\pi$-$\gamma$ transition form factor obtained within a perturbative approach which includes transverse momentum effects and Sudakov corrections. The results clearly favor distribution amplitudes close…
The meson-photon transition form factors $\gamma\gamma^*\to P$ ($P$ stands for $\pi$, $\eta$ and $\eta'$) provide strong constraints on the distribution amplitudes of the pseudoscalar mesons. In this paper, these transition form factors are…
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…
For the flavor-singlet heavy quark system of charmonia in the pseudoscalar ($\eta_c(1S)$) channel, we calculate the elastic (EFF) and transition form factors (TFF) ($\eta_c(1S) \rightarrow \gamma \gamma^*$) for a wide range of photon…