Related papers: Theoretical study on \eta'--> 4 pions

This talk describes the reasons why $\eta$ and $\eta^\prime$ decays are an interesting topic of study for both theory and experiment. The main part discusses the results of the recent calculation of $\eta\to3\pi$ at two-loop order in ChPT.…

The decays $J/\psi \rightarrow \gamma \pi^+\pi^-\pi^0$ and $J/\psi \rightarrow \gamma \pi^0\pi^0\pi^0$ are analyzed using a sample of 225 million $\jpsi$ events collected with the BESIII detector. The decay of $\eta(1405)\ar…

The extracted value for the $g^{eff}_{\omega \rho\pi}$ effective coupling from experimental data, considering only the $\rho$ meson, resumes not only the $\rho$ meson effect but also all its additional radial excitation modes. By explicitly…

The preliminary results of PIBETA experiment strongly suggest the presence of non V-A anomalous interactions in the radiative pion decay. Without a guiding idea about the nature of these new interactions it is very difficult to interpret…

Interactions of $a_2, K^*_2, f_2$ and $f_2'$ tensor-mesons with low-energy $\pi, K, \eta, \eta'$ pseudo-scalar mesons are constrained by chiral symmetry. We derive a chiral Lagrangian of tensor mesons in which the tensor mesons are treated…

We have studied radiative pion decays Pi+ -> e+ nu gamma in three broad kinematic regions using the PIBETA detector and a stopped pion beam. Based on Dalitz distributions of 42,209 events we have evaluated absolute Pi -> e nu gamma…

We study the |Delta I|=3/2 amplitudes of the octet-hyperon decays B -> B' + pion and of the decays Omega^- -> Cascade + pion in the context of heavy-baryon chiral perturbation theory. For the octet-hyperon decays, we investigate the…

The hard exclusive electroproduction of $\pi^0,\eta,\eta'$ mesons by the longitudinal photons is considered. We calculate the ratios of the $\pi^0 : \eta : \eta'$ yields for the electroproduction processes off nucleons and deuterons based…

In this article, we study the decays $\psi^{\prime}\to {J/\psi}\pi^+\pi^-$ and $\eta_c^{\prime}\to {\eta_c}\pi^+\pi^-$ by taking into account the chiral symmetry breaking effects, the final-state interactions and the heavy quark symmetry.…

We have studied the eta->pi+pi-e+e-(gamma) decay using about 1.7 fb^-1 collected by the KLOE experiment at the DAFNE phi-factory. This corresponds to about 72 millions eta mesons produced in phi radiative decays. We have measured the…

We report on an analysis of the decay $J/\psi\rightarrow\gamma\pi^0\eta^{\prime}$ using a sample of $(1310.6 \pm 7.0) \times ~10^6~ J/\psi$ events collected with the BESIII detector. We search for the CP-violating process…

We include the $\eta_c$ meson into the $\eta$-$\eta'$-$G$ mixing formalism constructed in our previous work, where $G$ represents the pseudoscalar gluball. The mixing angles in this tetramixing matrix are constrained by theoretical and…

In a small window of phase space, chiral perturbation theory can be used to make standard model predictions for tau decays into two and three pions. For $\tau \to 2\pi \nu_\tau$, we give the analytical result for the relevant form factor…

The effects of the anomalous contact terms are taken into account in tau to eta(eta')2pi nu decay. tau to 3pi nu is computed. Theoretical result agrees with data. It is the first time the anomalous vertex eta aa is tested. An a_{1}…

The decays of the eta meson are reviewed in the framework of Chiral Perturbation Theory. Particular attention is devoted to the electromagnetic channels involving photons, either in the final or intermediate states.

Using $(10087 \pm 44) \times 10^6$ $J/\psi$ events collected with the BESIII detector in 2009, 2012, 2018 and 2019, the tracking efficiency of charged pions is studied using the decay $J/\psi \rightarrow \pi^+ \pi^- \pi^0$. The systematic…

In this talk I give a short introduction to hard pion Chiral Perturbation Theory and an overview of the available applications $K\to\pi\pi$, $B,D\to D,\pi,K,\eta$ semileptonic decays and $\chi_{c0,2}\to\pi\pi,KK$. It is pointed out that the…

$\eta \rightarrow \pi^{0} \gamma \gamma$ and $\ggpipi$ are considered in $O(p^{6})$ chiral perturbation theory. In addition to the usual $\rho,\omega$ contributions, there are two $O(p^{6})$ operators (${\cal L}_{6,m}$) arising from…

We investigate what can be learnt about the $\eta$ -$\eta'$ mixing by means of dispersive representation of axial anomaly. We show that our method leads to the strong bounds for the $\eta-\eta'$ mixing angle: $\theta = -15.3^o \pm 1^o$.…

We investigate the most interesting decay processes involving axions, photons and the lightest pseudoscalar mesons, making use of a chiral effective Lagrangian model with $L=3$ light quark flavors, which also includes the flavor-singlet…