Abstract
Using 1.6 fb−1 of e + e − → ϕ → ηγ data collected with the KLOE detector at DAΦNE, the Dalitz plot distribution for the η → π + π − π 0 decay is studied with the world’s largest sample of ∼ 4.7 · 106 events. The Dalitz plot density is parametrized as a polynomial expansion up to cubic terms in the normalized dimensionless variables X and Y . The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX 2 Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.
Highlights
NNLO result depends on the values of a large number of the coupling constants of the chiral lagrangian which are not known precisely
The experiment is sensitive to all charge conjugation conserving terms of the expansion, including a gX2Y term
In the first approach the reliability of the calculations could be verified by a comparison with the experimental Dalitz plot data
Summary
The KLOE detector at the DAΦNE e+e− collider in Frascati consists of a large cylindrical Drift chamber (DC) and an electromagnetic calorimeter (EMC) in a 0.52 T axial magnetic field. Cluster energy is obtained from the signal amplitude and has a resolution of σ(E)/E = 5.7%/ E(GeV). The cluster position along the fibers is obtained from time differences of the signals. The trigger conditions are chosen to minimize beam background In this analysis, events are selected with the calorimeter trigger, requiring two energy deposits with E > 50 MeV for the barrel and E > 150 MeV for the endcaps. The interaction time is obtained event by event from the data exploiting the excellent timing performances of the calorimeter (230 ps for 50 MeV photons). The simulations of the background channels used in this analysis correspond to the integrated luminosity of the experimental data set, while the signal simulation corresponds to ten times larger luminosity
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