Related papers: Obtaining K to pi pi from Off-Shell K to pi Amplit…

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…

We propose a formalism to extract the $\gamma\pi\to\pi\pi$ chiral anomaly $F_{3\pi}$ from calculations in lattice QCD performed at larger-than-physical pion masses. To this end, we start from a dispersive representation of the…

To describe the weak three-body B decays into pi+ pi- K, we recently derived amplitudes based on two-body QCD factorization followed by pi+ pi- final state interactions in isoscalar S- and isovector P-waves. We study here the sensitivity of…

We calculate the $T$-matrices of elastic pion-nucleon ($\pi N$) scattering up to fourth order in SU(3) heavy baryon chiral perturbation theory. The pertinent low-energy constants are determined by fitting to $\pi N$ phase shifts below 200…

We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for $\pi\pi \to \pi\gamma^\star$, as a function of the energy of the $\pi\pi$ pair…

The chiral expansion of the $\pi\pi$ amplitude to the order of two loops was expressed in terms of six independent parameters in a previous paper: four of these are shown here to satisfy sum rules. Their derivation, where crossing symmetry…

I : Chiral Perturbation Theory is introduced and its applications to semileptonic and nonleptonic kaon decays are discussed. II: The method of large $N_c$ is used to calculate $K\to\pi\pi$ nonleptonic matrix elements, in particular the…

We study CP violation and the contribution of the strong kaon-pion interactions in the three body B --> K pi+ pi- decays. We extend our recent work on the effect of the two-pion S- and P-wave interactions to that of the corresponding…

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…

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…

A chiral quark-model approach is extended to the study of the $\bar{K}N$ scattering at low energies. The process of $K^-p\to \Sigma^0\pi^0$ at $P_K\lesssim 800$ MeV/c (i.e. the center mass energy $W\lesssim 1.7$ GeV) is investigated. This…

The renormalization, finiteness and off-shellness of short distance power like singular interactions is discussed. We show analytically that the renormalizability of the off-shell scattering amplitude relies completely on the corresponding…

Recent theoretical and numerical progresses of the lattice calculations of $K\to\pi\pi$ decay amplitude are reviewed.

The cross section for $\gamma\gamma\to\pi^0\pi^0$ and the pion polarizabilities are computed, within generalized chiral perturbation theory, in the full one loop approximation, {\it i.e.} up to and including order $O({p^5})$. The result…

The two-body decay rate of a weakly decaying particle (such as the kaon) is shown to be proportional to the square of a well-defined transition matrix element in finite volume. Contrary to the physical amplitude, the latter can be extracted…

The long distance contribution to $K^+ \to \pi^+ \nu {\bar \nu} $ is calculated using chiral perturbation theory. The leading contribution comes from $O(p^4)$ tree terms. The branching ratio of the $O(p^4)$ long distance contribution is…

In the heavy-quark limit, the hadronic matrix elements entering nonleptonic $B$-meson decays into two light mesons can be calculated from first principles including ``nonfactorizable'' strong-interaction corrections. The $B\to\pi K,\pi\pi$…

The five different CP conserving amplitudes for the decays $K\to3\pi$ are calculated using Chiral Perturbation Theory. The calculation is made to next-to-leading order and includes full isospin breaking. The squared amplitudes are compared…

In this talk, I first motivate the use of Chiral Perturbation Theory in the context of Lattice QCD. In particular, I explain how partially quenched QCD, which has, in general, unequal valence- and sea-quark masses, can be used to obtain…

Based on a dispersive approach, we apply the inverse amplitude method to unitarize one-loop SU(2) and SU(3) Chiral Perturbation Theory. Numerically, we find that this unitarization technique yields the correct complex analytic structure in…