Related papers: K_L -> pi pi e e in Chiral Perturbation Theory
The branching ratio of the rare decay pi0 -> e+ e- has been measured precisely, using the complete data set from the KTeV E799-II experiment at Fermilab. We observe 794 candidate pi0 -> e+ e- events using K0_L -> 3pi0 as a source of tagged…
Recent results on rare K decays from KTeV and NA48 are reviewed.
The perspectives of a search for the rare decay $K_L\to\pi^0\nu\bar{\nu}$ at a Phi-factory are discussed. After a general analysis, we focus on the realistic case of KLOE and DAFNE, showing that limits of the order of $10^{-9}$ on…
A detailed analysis to the [1,2] Pad\'e approximation to the $\pi\pi$ scattering 2--loop amplitudes in chiral perturbation theory is made.
The decay $\eta \to \pi^0 \gamma \gamma$ is discussed in the framework of SU(3) chiral perturbation theory. The process is dominated by the ${\cal{O}}(p^6)$ in the momentum expansion where tree-level amplitudes from the effective Lagrangian…
In a continuation of an ongoing program, we use staggered chiral perturbation theory to calculate the one-loop chiral logarithms and analytic terms in the pseudoscalar meson leptonic decay constants, $f_{\pi^+_5}$ and $f_{K^+_5}$. We…
We revisit the the rare kaon decays $K\to \pi l^+l^-$ which are of interest specially due to the recent measurements of the charged kaon decay spectra. We compute the contribution of the 27-plet to the decay amplitudes in one loop SU(3)…
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 dispersive two-photon contribution to the K_L --> mu+ mu- decay amplitude is analyzed, using chiral perturbation theory techniques and large-N_C considerations. A consistent description of the decays Pi^0 --> e+ e-, Eta --> mu+ mu- and…
The $\eta \to \pi^+ \pi^- \pi^0 \gamma$ decay is discussed in the general context of Chiral Perturbation Theory (ChPT), assuming that the low--energy constants (counter--terms) are saturated by vector-meson resonances. The $\eta \to \pi^+…
I discuss the status of ongoing work to determine numerically the elastic $\pi\pi$ scattering amplitude at order $p^6$ in the framework of chiral perturbation theory.
We present the matrix elements for the semileptonic kaon decays $K_{l2\gamma}$, $K_{l2l^+l^-}$, $K_{l2l'^+l'^-}$, $K_{l3}$, $K_{l3\gamma}$ and $K_{l4}$ at next-to-leading order in chiral perturbation theory and compare the predictions with…
The charged $K_{\ell 4}$ decay, $K^+\to\pi^+\pi^-\ell^+\nu_{\ell}$ is studied in the framework of chiral perturbation theory based on the effective Lagrangian including mesons, photons, and leptons. We give analytic expressions for the two…
We update the numerical results for the s-wave pi pi scattering phase-shift difference delta_0^0 - delta_0^2 at s = m_K^2 from a previous study of isospin breaking in K to 2 pi amplitudes in chiral perturbation theory. We include recent…
The decays tau -> 3 pi + nu(tau) are analyzed at one loop order in the framework of Generalized Chiral Perturbation Theory, in order to test the sensitivity to the size of spontaneous chiral symmetry breaking parameters, contained in the…
The CP conserved non leptonic $K\to \pi \pi \pi$ decays are discussed within the chiral quark model, including chiral perturbation theory corrections. All amplitudes are parameterized in terms of quark and gluon condensate and the…
The epsilon-impurity of the K_L wave-function gives rise to a huge CP-violating effect in the decay K_L -> pi^+ pi^- gamma which is hidden in the polarization state (Stokes vector) of the photon. One component of the Stokes vector is CP-odd…
I give an overview of the calculations done in three-flavour Chiral perturbation theory at next-to-next-to-leading order with an emphasis on those relevant for an improvement in the accuracy of the measurement of $V_{us}$. It is pointed out…
The hadronization structure of $\tau^- \to \eta \pi^- \pi^0 \nu_\tau$ decays is analyzed using Chiral Perturbation Theory with resonances, considering only the contribution of the lightest meson resonances at leading order in the $1/N_C$…
$K \rightarrow \pi \ell^+ \ell^-$ decays, $\ell = e, \mu$, will be one of the goals of future kaon facilities, like NA62 (CERN) and K$^0$TO (J-PARC). We review briefly the theoretical status of those processes.