Measurement of the branching ratio and search for a CP violating asymmetry in the η- π~+π~-e~+e~-(γ) decay at KLOE

摘要

We have studied the η -> π~+π~-e~+e~-(γ) decay using about 1.7 fb~(-1) collected by the KLOE experiment at the DAΦNE φ-factory. This corresponds to about 72 millions η mesons produced in φ radiative decays. We have measured the branching ratio, inclusive of radiative effects, with 4 accuracy: BR(η π~+π~-e~+e~-(γ)) = (26.8 ± 0.9_(Stat). ± 0.7_(Syst).) × 10~(-5). We have obtained the first measurement of the CP_odd ππ-ee decay planes angular asymmetry, A_φ = (-0.6 + 2.5_(Stat). ± 1.8_(Syst).) × 10~(-2).