相关论文: Two Photon Transition Form Factor of $\bar{c}c $ Q…

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…

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…

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…

We study photon--meson transition form factors $\gamma^*(Q^2)\gamma \to \pi^0,\eta,\eta'$ at low and moderately high virtualities $Q^2$ of one of the photons, the second photon being real. For the description of the form factor at low…

We shortly report on the two-photon decay width of the light $\sigma$-meson interpreted as a quarkonium state. Results are given in dependence on the $\sigma$-mass and the constituent mass of the light quark. The triangle quark-loop…

Within the framework of nonrelativistic QCD (NRQCD) factorization formalism, we compute the helicity amplitude as well as the decay width of $\eta_{Q2}$ ($Q=c,b$) electromagnetic decay into two photons up to next-to-next-to-leading order…

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 comment on a recent paper by Giacosa, Gutsche, and Lyobovitskij, in which it is argued that a quarkonium interpretation of the $\sigma$ meson should give rise to a much smaller two-photon decay width than commonly assumed. The reason for…

In this work, we discuss both relativistic and perturbative QCD corrections to the transition form-factor ${\cal F}_{\eta_Q}{(t_1,t_2)}$ for the process $\gamma^*(q_1) \gamma^*(q_2) \leftrightarrow \eta_Q(P)$ with dependencies on the…

We present an analysis of the recent measurement of $\eta'$-meson production by two virtual photons made by BaBar collaboration. It is the first measurement of a transition form factor which is entirely within the kinematic regime of the…

The two-photon width $\Gamma_{\gamma\gamma}$ of the $\eta_c$ meson has been measured with the L3 detector at LEP. The $\eta_c$ is studied in the decay modes $\pi^+\pi^-\pi^+\pi^-$, $\pi^+\pi^-$K$^+$K$^-$, K$_s^0$K$^\pm\pi^\mp$,…

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…

We study the N-Delta-gamma transition in the Dyson-Schwinger approach. The nucleon and Delta baryons are treated as quark-diquark bound states, where the ingredients of the electromagnetic transition current are computed self-consistently…

With the recent measurements on $\eta_{c}$ and $\eta_{c}^{\prime}$ at CLEO, Babar and Belle, and with the prospect of finding the $\eta_{b}$ at the Tevatron, it seems appropriate to have another look at the two-photon decay of heavy…

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 summarize recent work in determining the transition form factor (TFF) of the neutral pion ($\pi^0 \to \gamma^*\gamma^*$), by solving the non-perturbative Dyson-Schwinger and Bethe-Salpeter equations. We first study the transition form…

By neglecting the relative quark momenta in the propagator term, the two-photon and two-gluon decay amplitude of heavy quarkonia states can be written as a local heavy quark field operator matrix element which could be obtained from other…

Two-Body Dirac equations of constraint dynamics provide a covariant framework to investigate the problem of highly relativistic quarks in meson bound states. This formalism eliminates automatically the problems of relative time and energy,…

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…

In this work, we have investigated the physical properties like decay constants, radiative transitions, decay widths, and branching ratios for the ground and radially excited charmonia states. For the numerical calculations, we have adopted…