Related papers: The $\eta^\prime$ transition form factor from spac…

Using $(1310.6 \pm 7.0) \times 10^{6}~J/\psi$ events acquired with the BESIII detector at the BEPCII storage rings, the decay $\eta^\prime\rightarrow\pi^+\pi^-\mu^+\mu^-$ is observed for the first time with a significance of 8$\sigma$ via…

Motivated by more precise recent measurements of the $B \to \eta \ell \nu$ and $D_{(s)} \to \eta^{(\prime)}\ell \nu$ decays, we employ state-of-the-art parametrizations to describe the $B_{(s)}, D_{(s)} \to \eta^{(\prime)}$ form factors…

In the last years it became possible to measure in HADES the dilepton decays of several baryons. The baryon dilepton decays provide information about the electromagnetic structure of the baryons in the timelike region. In the present work,…

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…

Using a low background data sample of $9.7\times10^{5}$ $J\psi\rightarrow\gamma\eta^\prime$, $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the…

We study the processes $\gamma \gamma \to \eta_c \to \eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+e^-$…

We study the $\eta$-$\eta'$ mixing up to next-to-next-to-leading-order in $U(3)$ chiral perturbation theory in the light of recent lattice simulations and phenomenological inputs. A general treatment for the $\eta$-$\eta'$ mixing at higher…

At the turn of October and November 2008, the WASA-at-COSY collaboration performed an experiment to collect data on the eta meson decays in pd-->3He eta reactions. This report presents results of a study of the eta-->e+e-g conversion decay.…

The decays eta, eta-prime -> pi^+ pi^- gamma are investigated within an approach that combines one-loop chiral perturbation theory with a coupled channel Bethe-Salpeter equation which satisfies unitarity constraints and generates vector…

We present our model-independent and data-driven method to describe pseudoscalar meson transition form factors in the space- and (low-energy) time-like regions. The method is general and conforms a toolkit applicable to any other form…

Rare weak decays of $\eta^\prime\to K\pi$ have been investigated in the framework of the $U(3)$ chiral perturbation theory at the leading order. Our study shows that the branching ratio ${\cal B}(\eta^\prime\to K\pi)$ is of the order of…

The branching ratios of dilepton anomalous decays $\eta^{(\prime)}\to\pi^+\pi^-l^+l^-$, where $l=e,\mu$, are calculated in the framework of the Nambu -- Jona-Lasinio model. Particular attention is paid to studying the hadronic perturbative…

The $\eta$-$\eta^\prime$ mixing angle is deduced from an updated phenomenological analysis of $J/\psi$ decays into a vector and a pseudoscalar meson. Corrections due to non-ideal $\omega$-$\phi$ mixing are confirmed to be crucial to find…

Based on a sample of $1.31$ billion $J/\psi$ events collected with the BESIII detector, we report the study of the doubly radiative decay $\eta^\prime\to \gamma\gamma\pi^0$ for the first time, where the $\eta^\prime$ meson is produced via…

Based on 3.19 fb$^{-1}$ of $e^+e^-$ collision data accumulated at the center-of-mass energy 4.178 GeV with the BESIII detector operating at the BEPCII collider, the electromagnetic Dalitz decay $D^{\ast 0}\to D^{0}e^{+}e^{-}$ is observed…

Using 7.33 fb$^{-1}$ of $e^+e^-$ collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV, we observe for the first time the decay $D^{\pm}_s\to \omega\pi^{\pm}\eta$ with a statistical…

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…

Hadronic decay modes $D^0\to(\bar K^0, \bar K^{*0})\eta,\eta'$ and $(D^+,D_s^+)\to(\pi^+,\rho^+)\eta,\eta'$ are studied in the generalized factorization approach. Form factors for $(D,D_s^+)\to(\eta,\eta')$ transitions are carefully…

The mixing of $\eta-\eta'$ or $\eta-\eta'-G$ is of a great theoretical interest, because it concerns many aspects of the underlying dynamics and hadronic structure of pseudoscalar mesons and glueball. Determining the mixing parameters by…

Using 2.92 fb$^{-1}$ of electron-positron annihilation data collected at a center-of-mass energy of $\sqrt{s}= 3.773$ GeV with the BESIII detector, we present an improved measurement of the branching fraction $\mathcal{B}(D^+ \to \omega e^+…