No Arabic abstract
A sample of 1.25x10^9 phi decays, collected with the KLOE detector at the Frascati phi-factory DAFNE at center of mass energy ~ Mphi, has been used to study the radiative decay phi to eta pi0 gamma. This decay is dominated by phi to a0(980) gamma. Two decay chains, corresponding to eta to gamma gamma and eta to pi+ pi- pi0, have been selected. We found respectively: Br(phi to eta pi0 gamma)=(6.92 +/- 0.10 (stat.) +/- 0.20 (syst.))x10^(-5) and (7.19 +/- 0.17 (stat.) +/- 0.24 (syst.))x 10 ^(-5). The eta pi0 invariant mass distributions have been fitted to obtain the relevant a0(980) parameters.
We have studied the phi->a_0(980) gamma process with the KLOE detector at the Frascati phi-factory DAPhNE by detecting the phi->eta pi^0 gamma decays in the final states with eta->gamma gamma and eta->pi^+ pi^- pi^0. We have measured the branching ratios for both final states: Br(phi->eta pi^0 gamma)=(7.01 +/- 0.10 +/- 0.20)x10^-5 and (7.12 +/- 0.13 +/- 0.22)x10^-5 respectively. We have also extracted the a_0(980) mass and its couplings to eta pi^0, K^+ K^-, and to the phi meson from the fit of the eta pi^0 invariant mass distributions using different phenomenological models.
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta --> gammagamma and 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +- 0.7)x10^-5.
We present a study of the reaction e+e- --> pi+pi-pi0 at the phi peak W=M(phi)=1019.4 MeV observed with the KLOE detector at Dafne. The reaction is dominated by phi production and decay, e+e- --> phi --> pi+pi-pi0. From a fit to the Dalitz plot density distribution we obtain the rho-meson parameters for its three charge states. We also find the relative amplitudes for phi --> rhopi and phi -> pi+pi-pi0 and the cross-section for e+e- --> omega pi0 with omega --> pi+pi-.
We have studied the vector to pseudoscalar conversion decay phi -> eta e+e-, with eta -> pi0pi0pi0, with the KLOE detector at DAPHNE. The data set of 1.7 fb-1 of e+e- collisions at sqrt(s)~Mphi contains a clear conversion decay signal of ~31,000 events from which we measured a value of BR(phi -> eta e+e-)=(1.075+-0.007+-0.038)x10-4. The same sample is used to determine the transition form factor by a fit to the e+e- invariant mass spectrum, obtaining b(phi eta) =(1.17 +- 0.10 + 0.07) GeV-2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations.
Using samples of 2.25*10^8 J/psi events and 1.06*10^8 psi events collected with the BES III detector, we study the f0(980) to a0(980) and a0(980) to f0(980) transitions in the processes J/psi --> phi f0(980) --> phi a0(980) and chi_c1 --> pi^0 a0(980) --> pi^0 f0(980), respectively. Evidence for f0(980) --> a0(980) is found with a significance of 3.4 sigma, while in the case of a0(980) --> f0(980) transition, the significance is 1.9 sigma. Measurements and upper limits of both branching ratios and mixing intensities are determined.