Related papers: Once again about the reaction phi(1020)-> gamma-pi…

In this manuscript we comment on the criticism raised recently by Achasov and Kiselev [Phys. Rev. D 76, 077501 (2007)] on our work on the radiative decays phi to gamma a_0/f_0 [Eur. Phys. J. A 24, 437 (2005)]. Specifically, we demonstrate…

The \phi\to\gamma\pi\pi amplitude is found from the e+e-\to\gamma\pi\pi amplitude suggested in Ref. hep-ph/0606266. It is shown that the found amplitude differs essentially from that studied in Refs. hep-ph/0606266 and [3]. It is noticed…

We calculate the $00^{++}$-wave two-meson spectra for the reactions $\gamma\gamma\to\pi^0\pi^0$, $\gamma\gamma\to\pi^+\pi^-$, $\gamma\gamma\to K^0\bar K^0$ and $\gamma\gamma\to K^+ K^-$ on the basis of: (i) the results of the $K$-matrix…

The amplitude for the anomalous transitions gamma pi(+) -> pi(0) pi(+) is analyzed within Chiral Perturbation Theory including electromagnetic interactions. The presence of a t-channel one-photon exchange contribution induces sizeable e^2…

It is argued that the realization of gauge invariance condition as a consequent of cancellation between the \phi\to\gamma f0\to\gamma\pi0\pi0 resonance contribution and a \phi\to\gamma\pi0\pi0 background one, suggested in Ref. [1], is…

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…

The gamma p ---> pi+ pi- p reaction, in combination with data from the pi N ---> pi pi N reaction, allows one to obtain the s- and d-wave amplitudes for the N*(1520) decay into Delta pi with absolute sign with respect to the N*(1520) ---> N…

Preliminary results on the study of e+e- --> phi(1020) --> pi0 pi0 gamma, eta pi0 gamma processes from SND experiment at VEPP-2M collider in Novosibirsk are presented. Branching ratios of rare radiative phi --> pi0 pi0 gamma and phi --> pi0…

The constraints followed from gauge invariance and analyticity are considered for the amplitudes of radiative transitions of composite systems when composite systems are treated in terms of spectral integrals. We discuss gauge-invariant…

We analyze the existing data on the angular distributions of the $\gamma\gamma\to \pi^+ \pi^- ,\pi^0 \pi^0$ reactions with using of the unitary model for helicity 2 amplitude. The purpose is to obtain the D--wave parameters and S--wave…

The most general amplitude for the radiative pion decay pi -> e nu gamma including terms beyond V-A theory is considered. The experimental constraints on the decay amplitude components are discussed. A model independent presentation of the…

Using 11.6 pb^{-1} of data collected in the energy range 0.984--1.06 GeV by CMD-2 at VEPP-2M, the cross section of the reaction e+e- to pi+pi-pi+pi- has been studied. For the first time an interference pattern was observed in the energy…

We complete the recalculation of the available two-loop expressions for the reaction \gamma\gamma->\pi\pi in the framework of chiral perturbation theory. Here, we present the results for charged pions. The cross section and the values of…

The $\pi\pi$ scattering amplitude with regular analytical properties in the $s$ complex plane has been constructed. It describes simultaneously the data on the $\pi\pi$ scattering, $\phi\to\pi^0\pi^0\gamma$ decay and $\pi\pi\to K\bar K$…

For the gamma-pion interaction, the perturbative expansion of the effective chiral Lagrangian (chi-PT) can be limited to terms quartic in momenta and masses (O(p4)), or to higher order. The abnormal intrinsic parity (chiral anomaly)…

Differential cross sections of the reactions $(\gamma,\pi^\circ\pi^\circ)$ and $(\gamma,\pi^\circ\pi^++\pi^\circ\pi^-)$ have been measured for several nuclei ($^1$H,$^{12}$C, and $^{\rm nat}$Pb) at an incident-photon energy of…

The lowest-lying resonance in the QCD spectrum is the $0^{++}$ isoscalar $\sigma$ meson, also known as the $f_0(500)$. We augment SU(2) chiral perturbation theory ($\chi$PT) by including the $\sigma$ meson as an additional explicit degree…

The Ward-Takahashi identities are central to the gauge invariance of the photoproduction amplitude. Here we demonstrate that unitarity and in particular the inclusion of both the $\pi N$ and $\gamma\pi N$ thresholds on equal footing yields…

The process e+e- ->pi+pi- has been studied with the SND detector at VEPP-2M e+e- collider in the vicinity of phi(1020) resonance. From the analysis of the energy dependence of measured cross section the branching ratio…

The reaction e^+e^- ---> OMEGA+PI0 ---> PI+PI- 2PI0 has been studied with SND detector at VEPP-2M e^+e^- collider in the vicinity of the PHI(1020) meson resonance. The observed interference pattern in the energy dependence of the cross…