Related papers: Study of Gamma + Pi --> Pi + Pi
The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have…
The experimental data on the processes $\pi\pi\to\pi\pi,K\bar{K},\eta\eta,\eta\eta^\prime$ in the $I^GJ^{PC}=0^+0^{++}$ channel have been jointly analyzed to study the status and nature of the $f_0$. The method of analysis is based on…
The form factor for the anomalous process gamma pi^+ -> pi^+ pi^0, which is presently being measured at CEBAF, is calculated in the Schwinger-Dyson approach in conjunction with an impulse approximation. The form factors obtained by us are…
Elastic pi N scattering and the reaction pi+ p --> K+ Sigma+ are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u-channel exchanges that drive…
Once and twice subtracted crossing symmetric dispersion relations applied to $\pi\pi \to \pi\pi$ scattering data are analyzed and compared. Both sets of dispersion relations can be used to test the $\pi\pi$ amplitudes in low partial waves…
A dispersive representation based on unitarity and analyticity is used to study the low energy $\gamma N \to \pi N\ \text{and}\ \gamma^* N \to \pi N$ partial wave amplitudes. Final state interactions of the $\pi N$ system are critical to…
We present a new, model-independent method to analyze radiative decays of mesons to a vector, isovector pair of pions of invariant mass square below the first significant pion-pion threshold in the vector channel. It is based on a…
We evaluate the amplitude for gamma gamma --> pi^+ pi^- to two loops in the framework of chiral perturbation theory.The three new coupling constants that enter the result at this order in the low-energy expansion are estimated via resonance…
In production processes, e.g. J/Psi -> omega-pi-pi or pbar-p -> 3pi, the sigma and fo(980) overlap in the same partial wave. The conjecture of Extended Unitarity (EU) states that the pi-pi pair should have the same phase variation as pi-pi…
We study the process $\gamma\gamma\to\pi^0\pi^0$ involving the principle mechanisms, the structure of its cross section and the role of individual isoscalar-tensor resonances in the saturation of its energy spectrum.
A new unitarization approach is discussed and applied to study the elastic $\pi K$ scattering process. The existence of the light $\kappa$ resonance is firmly established if the scattering length in the I=1/2 channel does not deviate too…
A new approach to the analysis of three body decays is presented. Measurements of the S-wave K pi amplitude are made in independent ranges of invariant mass from threshold up to the upper kinematic limit in D+ to K-pi+pi+ decays. These are…
A joint analysis of the pi+pi- and pi0pi0 S-wave amplitudes including results of three experiments has been performed. Using our theoretical model of the pion-pion production in which not only the pion exchange but also the a1(1260) meson…
Using a low background data sample of $9.7\times10^{5}$ $J\psi\rightarrow\gamma\eta^\prime$, $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the…
We describe the interference between amplitudes $e^+e^- \to \rho \to \gamma\pi^+\pi^-$ and $e^+e^- \to \phi \to \gamma f_0 \to \gamma\pi^+\pi^-$, where $f_0$ meson is considered in the frameworks of the four-quark model and the model of the…
Starting from hyperbolic dispersion relations, we present a system of Roy--Steiner equations for pion Compton scattering that respects analyticity and unitarity requirements, gauge invariance, as well as crossing symmetry, and thus all…
A precision measurement of absolute pi+p and pi-p elastic differential cross sections at incident pion laboratory kinetic energies from T_pi= 141.15 to 267.3 MeV is described. Data were obtained detecting the scattered pion and recoil…
We study the excitation spectrum of light and strange mesons in diffractive scattering. We identify different hadron resonances through partial wave analysis, which inherently relies on analysis models. Besides statistical uncertainties,…
We carry out the semi--model analysis of existing data on the angular distributions of the $\gamma\gamma\rightarrow\pi^+ \pi^- ,\ \pi^0 \pi^0$ reactions with purpose to obtain S-wave cross section and D-wave's parameters. In the first time…
Roy's equations are used to check if scalar-isoscalar pi-pi amplitudes fitted to the ``up-flat'' and ``down-flat'' phase shift solutions fulfill crossing symmetry below 1 GeV. It is shown that the amplitude fitted to the ``down-flat''…