Abstract
The KLOE detector is operational since spring '99 at DAΦNE, the Frascati e+e- collider, a ϕ-factory running at 1.02 GeV c.m. energy. This detector has been designed and built with the primary goal of measuring Re(ε' / ε), the CP violation parameter in the kaon system, with a sensitivity of about one part in ten thousands. Apart from CP studies in the kaon system, KLOE has a rich scientific program that can be exploited with an integrated luminosity not far from the one which has already been collected, namely the study of ϕ decays into scalar and pseudoscalar mesons, the measurement of the hadronic cross-section up to 1 GeV, rare kaon decays, ϕ decays into three pions. Since the detector installation there have been three periods of stable data taking and a total amount of ~200 pb-1 has been collected by end of 2001, corresponding to ~6.7 · 108 ϕ mesons and to ~8.7 · 106 η mesons, being BR(ϕ → ηγ) = (1.297±0.033) · 10-2.
We present the results obtained, for a data sample of 17 pb-1 collected in the year 2000, for ϕ → ηγ and ϕ → η'γ: the ratio of these two BR's has been measured to be (5.3 ± 0.5 ± 0.4) · 10-3, leading to a very accurate determination of the mixing angle in the flavor basis φP = (40+7.5-1.5)° and to the most accurate determination of BR(ϕ → η'γ) to date; (6.8 ± 0.6 ± 0.5) · 10-5. From the ratio BR(ϕ → η'γ)/BR(ϕ → π0γ) we have extracted the value BR(ϕ → π0γ) = (1.377 ± 0.007 ± 0.05) · 10-3.
Export citation and abstract BibTeX RIS