No Arabic abstract
We report on a new measurement of the branching ratio B(KL->pi0 gamma gamma)using the KTeV detector. We reconstruct 1982 events with an estimated background of 608, that results in B(KL -> pi0 gamma gamma) = (1.29 +/- 0.03(stat) +/- 0.05(syst)) x 10**-6. We also measure the parameter, aV, which characterizes the strength of vector meson exchange terms in this decay. We find aV = -0.31 +/- 0.05(stat) +/- 0.07(syst). These results utilize the full KTeV data set collected from 1997 to 2000 and supersede earlier KTeV measurements of the branching ratio and aV.
We report on a new measurement of the branching ratio B(KL -> pi0 e+ e- gamma) using the KTeV detector. This analysis uses the full KTeV data set collected from 1997 to 2000. We reconstruct 139 events over a background of 14, which results in B(KL -> pi0 e+ e- gamma) = (1.62 +/- 0.14 (stat) +/- 0.09 (syst)) x 10^{-8}. This result supersedes the earlier KTeV measurement of this branching ratio.
We report on the first observation of the decay KL -> pi0 ee gamma by the KTeV E799 experiment at Fermilab. Based upon a sample of 48 events with an estimated background of 3.6 +/- 1.1 events, we measure the KL -> pi0 ee gamma branching ratio to be (2.34 +/- 0.35 +/- 0.13)x10^{-8}. Our data agree with recent O(p^6) calculations in chiral perturbation theory that include contributions from vector meson exchange through the parameter a_V. A fit was made to the KL -> pi0 ee gamma data for a_V with the result -0.67 +/- 0.21 +/- 0.12, which is consistent with previous results from KTeV.
We present new results on the related rare KL decay modes KL -> pi+ pi- gamma and KL -> pi+ pi- e+ e-. KTeV has performed the first direct measurement of the form factor for the direct emission component of KL -> pi+ pi- gamma decays, a quantity with ramifications for particular chiral models. In addition, the form factor and direct emission/inner bremsstrahlung branching ratio - also presented here - are important input parameters for the understanding of the planar-angle distribution of KL -> pi+ pi- e+ e- decays. Preliminary results indicating the presence of a T-violating asymmetry in the KL -> pi+ pi- e+ e- angular distribution are presented.
Signal of the rare radiative decay PHI--->ETA+PI0+GAMMA was observed in the SND experiment at VEPP-2M electron-positron collider.The result is based on the analysis of data, corresponding to a total integrated luminosity of 4 pb^{-1}, or 8x10^6 PHI mesons produced. The measured branching ratio of PHI--->ETA+PI0+GAMMA decay is equal to (0.83+-0.23)x10^{-4}.
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 eta gamma decays are measured: B(phi --> pi0 pi0 gamma ) = (1.1 +- 0.2) * 10^-4 (invariant mass (pi0 pi0) < 800 MeV), B(phi --> eta pi0 gamma ) = (1.3 +- 0.5) * 10^-4.