Related papers: pi^0-eta Mixing and CP Violation
We improve the calculations of the $\eta \to \pi^0 \gamma \gamma$ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the $a_0(980)$ resonance and fixing…
Weak interaction contributions to the strong theta parameter are revisited in the frame of a large-Nc Chiral Perturbation Theory. Focusing on the hadronic (eta,etaprime) \to pi pi amplitudes, we express these second-order corrections in…
A complete analysis of isospin breaking in $K\to 2\pi$ amplitudes, including both strong and electromagnetic corrections at next-to-leading order in chiral perturbation theory, has been achieved recently. We discuss the implication of these…
The two photon decay width of the neutral pion is analyzed within the combined framework of Chiral Perturbation Theory and the 1/Nc expansion up to order p^6 and p^4 times 1/Nc in the decay amplitude. The eta' is explicitly included in the…
A phenomenological analysis on various decay processes is performed using an energy-dependent $\eta-\eta'$ mixing angle scheme. Special attention is given to the radiative couplings between lowest-lying vector and pseudoscalar mesons. The…
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…
We investigate the $\eta^\prime \to \eta \pi\pi$ decays within the framework of large-$N_{C}$ chiral perturbation theory, by calculating the decay amplitudes up to next-to-next-to-leading order in a simultaneous expansion in powers of…
The strong isospin-breaking correction, Omega_{st}, which appears in estimates of the Standard Model value for the direct CP-violating ratio epsilon'/epsilon, is evaluated to next-to-leading order (NLO) in the chiral expansion using Chiral…
In the framework of the "current scheme" of $\eta - \eta'$ mixing we calculate the amplitude of the decay $\eta' \to \pi ^+ \pi ^- \gamma $ in the soft limit and compare our results with recently reported values of the phenomenological…
We demonstrate that the decay eta -> 3 pi represents a sensitive probe for the breaking of chiral symmetry by the quark masses. The transition amplitude is proportional to the mass ratio (m_d^2-m_u^2)/(m_s^2-m^2). The factor of…
The hadronic decays eta' -> eta pi pi are studied in the frameworks of large-Nc Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/Nc approximation. Higher order effects such as…
In this paper, U(3)$_L\times$ U(3)$_R$ chiral theory of mesons is extended to the leading order in quark mass expansion in order to evaluate the $\rho^0-\omega$ mixing. It is shown that the use of path integral method to integrate out the…
We calculate the branching ratios of the yet unmeasured eta' decays into four pions, based on a combination of chiral perturbation theory and vector-meson dominance. The decays eta' --> 2(pi+ pi-) and eta' --> pi+ pi- 2pi0 are P-wave…
A reliable determination of the isospin breaking double quark mass ratio from precise experimental data on $\eta\to 3\pi$ decays should be based on the chiral expansion of the amplitude supplemented with a Khuri-Treiman type dispersive…
We improve the calculations of the $\eta \to \pi^0 \gamma \gamma$ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the $a_0(980)$ resonance and fixing…
In this work the analysis of mixing parameters of the system involving eta, eta' mesons and some third massive state G is carried out. We use the generalized mixing scheme with three angles. The framework of the dispersive approach to…
Using psi(2S) --> pi+ pi- J/psi, J/psi --> gamma eta' events acquired with the CLEO-c detector at the CESR e+e- collider, we make the first observations of the decays eta' --> pi+ pi- pi0 and eta' --> pi+ pi- e+ e-, measuring absolute…
We analyse $K^- p \to (\eta, \eta',\pi^0) \Lambda$ on the basis of the fit of data in a wide region of energies, and $\pi^- p \to (\eta, \eta') n$ at the energies of GAMS-4$\pi$. We show that disagreements between the data and the…
We extend a recent calculation of the momentum dependence of the $\rho-\omega$ mixing amplitude to the pseudoscalar sector. The $\pi\!-\!\eta$ mixing amplitude is calculated in a hadronic model where the mixing is driven by the…
Underlying mixing of scalar mesons is studied in $\eta'\rightarrow \eta\pi\pi$ decay within a generalized linear sigma model of low-energy QCD which contains two nonets of scalar mesons and two nonets of pseudoscalar mesons (a…