Related papers: Feynman rules for the strong and $\Delta S =1$ wea…
We use the chiral quark model to estimate the coefficients of the weak chiral lagrangian as obtained from the bosonization of the ten relevant operators of the $\Delta S = 1$ effective quark lagrangian. All contributions of order $N_c^2$ as…
An overview is presented about old and recent methods to compute the $K\to \pi \pi$ decay amplitude.
I calculate the leading logarithmic contributions up to two-loop order of the octet part of the K -> pi pi amplitude. This sector of the weak chiral Lagrangian is believed to be the main source of the enhancement of the I=0 relative to the…
It is proposed to compute matrix elements for the (unphysical) $K^0\pi^-\to \pi^-$ transition to determine the next-to-leading order low energy constants of the weak chiral Lagrangian. This allows us to evaluate $K\to(\pi\pi)_{I=0}$ decay…
The decays $K \to \pi l^{+} l^{-}$, $K \to \pi \gamma \gamma $ and $K \to \pi \nu {\bar \nu}$ are investigated using the higher order terms of the chiral perturbation theory. The counterterms induced by strong, weak and electromagnetic…
We study a new $K\rightarrow\pi\pi$ decay channel with gluons in intermediate state which is normally neglected within the factorization framework. Both short-distance and long-distance parts of the amplitude are calculated. The chiral…
In the absence of nucleons, we use partial wave unitarity, to show that the chiral expansion parameter must be close to $p^2/4\pi f_{\pi}^2$ rather than $p^2/16\pi^2 f_{\pi}^2$ as previously suggested, where $p$ is a typical pion momentum…
We present the recent investigation of the $\Delta S = 1$ effective weak chiral Lagrangian within the framework of the instanton-induced chiral quark model. Starting from the effective four-quark operators, we derive the effective weak…
We investigate the $\Delta S = 1,2$ effective weak chiral Lagrangian within the framework of the chiral quark model. Starting from the effective four-quark operators, we derive the effective weak chiral action by integrating out the…
We present a new analysis of the Delta I = 1/2 rule in K --> pi pi decays and the B_K parameter. We use the 1/N_c expansion within the effective chiral lagrangian for pseudoscalar mesons and compute the hadronic matrix elements at leading…
The decays $K^{+} \rightarrow \pi^{+} e^{+} e^{-}$, $K_{S} \rightarrow \pi^{0} e^{+} e^{-}$ and $K_{L} \rightarrow \pi^{0} e^{+} e^{-}$ are reinvestigated within the framework of chiral perturbation theory. The counterterms induced by…
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…
We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light. They are extracted by comparing the predictions…
The $K\to\pi\pi$ decay amplitudes are studied within the framework of generalized factorization in which the effective Wilson coefficients are gauge-invariant, renormalization-scale and -scheme independent while factorization is applied to…
We analyze long-distance contributions to the K --> pi pi amplitudes relevant for the Delta I = 1/2 selection rule in the framework of the 1/N_c expansion. We use a modified prescription for the identification of meson momenta in the chiral…
We study the chiral logarithms in $\Delta S=1$ kaon decay amplitudes from new flavor physics in beyond-standard-model theories. We systematically classify the chiral structures of dimension-5, 6 and 7 effective QCD operators constructed out…
The CP conserving amplitudes for the decays $K\to3\pi$ are calculated in Chiral Perturbation Theory. The calculation is made at the next-to-leading order including strong and local electromagnetic isospin breaking. A comparison is made…
The Chiral Confining Lagrangian, based on the chiral theory with quark degrees of freedom, is used to study the spectroscopy of scalar mesons. The formalism does not contain arbitrary fitting parameters and takes into account infinite…
We present a calculation of the low energy constants describing the real and imaginary parts of the $K \to \pi \pi$ decay amplitudes $A_0$ and $A_2$. Leading and next leading order chiral perturbation theory is used and its applicability…
The decay modes $\rho^0 \to 2\pi^+ 2\pi^-$ and $\rho^0 \to 2\pi^0 \pi^+ \pi^-$ are considered in the framework of the low energy effective chiral Lagrangian. The obtained values of the decay widths $\Gamma(\rho^0\to 2 \pi^+ 2 \pi^-)=$ $(16…