Related papers: Two-photon transitions of charmonia on the light f…
We investigate E1 radiative transitions within charmonium in a relativistic approach based on light-front QCD. In quantum field theory, two sets of processes are pure E1: $\chi_{c0} \to J/\psi \gamma$ ($\psi\to \chi_{c0}\gamma$) and $h_c…
We continue our work on the light-front formulation of quarkonium $\gamma^* \gamma$ transition form factors, extending the formalism to $J^{PC} = 2^{++}$ tensor meson states. We present an analysis of $\gamma^* \gamma \to \chi_{c2}$…
We make the first calculation in lattice QCD of two-photon decays of mesons. Working in the charmonium sector, using the LSZ reduction to relate a photon to a sum of hadronic vector eigenstates, we compute form-factors in both the…
In this paper, a study of two-photon and two-gluon decays in the context of p-wave heavy quarkonia is presented. Within the covariant light-front framework, the annihilation rates of scalar and tensor quarkonium states are derived. In the…
This review briefly outlines recent experimental results from the charmonium system. These include new measurements of the M1 radiative transition rates $B(\psi(1S,2S)\to\gamma\eta_c(1S))$; new insights into the mass of the $\eta_c(1S)$;…
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…
The form factors for the radiative transitions between charmonium mesons are investigated. We employ an anisotropic lattice using a Wilson gauge action, and domain-wall fermion action. We extrapolate the form factors to $Q^2 = 0$,…
Using a data sample of 24.5 million psi(2S) the reactions psi(2S)->gamma chi_cJ, chi_cJ->gamma gamma have been studied for the first time to determine the two-photon widths of the chi_cJ states of charmonium in their decay into two photons.…
We investigate the gravitational form factors of charmonium. Our method is based on a Hamiltonian formalism on the light front known as basis light-front quantization. The charmonium mass spectrum and light-front wave functions were…
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…
In the covariant light-front quark model, we investigate the $B_c\to h_c, \chi_{c0,1,2}$ form factors. The form factors are evaluated in space-like kinematic region and are recasted to the physical region by adopting the exponential…
We predict the $\mathcal{V} \to \mathcal{P} \gamma$ decay widths and the $\mathcal{V} \to \mathcal{P} \gamma^{*}$ transition form factors, where $\mathcal{V}=(\rho, \omega, K^*, \phi)$ and $\mathcal{P}= (\pi,K, \eta,\eta^\prime)$, using…
The study of electron-positron collisions at center-of-mass energies corresponding to charmonium production has reached new levels of sensitivity thanks to experiments by the BES and CLEO Collaborations. Final states $\gamma P$, where $P$…
The two-photon width of chi_c2 (^3P_2) state of charmonium has been measured using 14.4 fb^-1 of e+e- data taken at sqrt{s} = 9.46-11.30 GeV with the CLEO III detector. The two-photon fusion reaction studied is e+e- -> e+e- gamma gamma,…
We study the semileptonic decay of the $B_c (0^-)$ to charmonia through the bottom-to-charm-quark electroweak current in the framework of basis light-front quantization. Explicitly, we calculate the weak transition form factors for…
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…
We review our recent results for production of $\eta_c(1S)$ and $\eta_c(2S)$ in the $\gamma^* \gamma^* \to \eta_c(1S,2S)$ fusion and in proton-proton collisions via gluon-gluon fusion. The quarkonium wave functions are calculated by solving…
We study heavy quarkonium within the light-front Hamiltonian formalism. Our effective Hamiltonian is based on the holographic QCD confining potential and the one-gluon exchange interaction with a running coupling. The obtained spectra are…
Recent BABAR results on two-photon processes are presented. A high statistics study of the two-photon production of the charmonium states eta_c and eta_c(2S) is performed. The mass and width of eta_c and eta_c(2S) are measured; the ratio of…
The analysis of the $\pi\gamma$ transition form factor provides severe constraints on the pion's wave function. This information is used to examine charmonium decays into two pions critically. It will be argued that the standard…