Related papers: Study of Gamma + Pi --> Pi + Pi
The master formula approach to chiral symmetry breaking is used to analyze the phase shifts for $\pi\pi$ scattering in the elastic region. The results are in excellent agreement with the data for the phase shifts up to the K-K bar…
A method is proposed to measure the photon polarisation parameter $\lambda_\gamma$ in $b\to s\gamma$ transitions using an amplitude analysis of $B\to K\pi\pi\gamma$ decays. Simplified models of the $K\pi\pi$ i system are used to simulate…
We review the recent measurements of the rare pion decays: Pi+ -> Pi0 e+ Nu [pion beta, Pi_(e3), or Pi_beta decay], radiative decay Pi+ -> e+ Nu Gamma [Pi_(e2Gamma) or RPD], and Pi+ -> e+ Nu [Pi_(e2)] decay, as well as the radiative muon…
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…
Hadronic (Pi+Pi-) atom is studied in the relativistic perturbative approach based on the Bethe-Salpeter equation. The general expression for the atom lifetime is derived. Lowest-order corrections to the relativistic Deser-type formula for…
We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor.)) x 10^{-8}. We compare this result with predictions from…
We discuss the reaction $\pi^- e^- \to \pi^- e^- \pi^{0}$ with the purpose of obtaining information on the $\gamma \pi \to \pi\pi$ anomalous amplitude ${\cal F}_{3\pi}$. We compare a full calculation at ${\cal O}(p^6)$ in chiral…
We evaluate analytically the elastic $\pi\pi$ scattering amplitude to two loops in chiral perturbation theory and give numerical values for the two $S$--wave scattering lengths and for the phase shift difference $\delta_0^0-\delta_1^1$.
A dispersion integral is derived that connects data on $\eta\to \pi^+\pi^-\gamma$ to the $\eta\to \gamma\gamma^*$ transition form factor. A detailed analysis of the uncertainties is provided. We find for the slope of the $\eta$ transition…
We study the long-distance dominated K_L -> pi^+ pi^- gamma decay at O(p^6) in Chiral Perturbation Theory. The complete calculation of the O(p^6) loop magnetic amplitude is carried out. At this chiral order the model dependent part of the…
We study pi eta scattering in a model which starts from the tree diagrams of a non-linear chiral Lagrangian including appropriate resonances. Previously, models of this type were applied to pi pi and pi K scattering and were seen to require…
We present a data-driven analysis of the S-wave $\pi\pi \to \pi\pi\,(I=0,2)$ and $\pi K \to \pi K\,(I=1/2, 3/2)$ reactions using the partial-wave dispersion relation. The contributions from the left-hand cuts are parametrized using the…
We report the measurement of the ratio $\Gamma(\eta \to \pi^+\pi^-\gamma)/\Gamma(\eta \to \pi^+\pi^-\pi^0)$ analyzing a large sample of $\phi \to \eta \gamma$ decays recorded with the KLOE experiment at the DA$\Phi$NE $e^+ e^-$ collider,…
Using chiral low energy theorems and elastic unitarity assumption, the $\tau\to\pi K \nu $ decay is investigated. The vector and scalar $\pi K$ form factors are calculated. It is found that the $\pi K$ spectrum is dominated by the $K^*$…
We use the Linear Sigma Model to test the convergence of different sequences of Pade Approximants when used to unitarize the low energy pi-pi scattering amplitude. We find that, in this particular case, diagonal sequences reproduce the…
The low-energy S-wave component of the decay $D^+ \to K^- \pi^+ \pi^+$ is studied by means of a chiral SU(3)XSU(3) effective theory. As far as the primary vertex is concerned, we allow for the possibility of either direct production of…
We consider the forward-backward pion charge asymmetry for the e^{+}e^{-}\to\pi^{+}\pi^{-}\gamma process. At tree level we consider bremsstrahlung and double resonance contributions. Although the latter contribution is formally sub-leading,…
We present a method for measuring the weak phase gamma using isospin analysis of three body B decays into K pi pi channels. Differential decay widths and time dependent asymmetry in B_d -> K_s pi^+pi^- mode needs to be measured into even…
The charge asymmetry in the process $e^+e^-\to \pi^+\pi^-\pi^0\gamma$ is studied for photons with energies $\nu\ll\sqrt{s}$. The longitudinal polarization of electrons (positrons) is taken into account. The asymmetry arises due to…
Perturbative partial-wave amplitudes diverge in cases with a massless exchanged particle in the $t$-channel. We argue that the divergence is an artifact of perturbation theory and give a prescription for the all-orders correction factor…