Precision measurement of the η→π+π−π0 Dalitz plot distribution with the KLOE detector

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−π0 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 gX2Y term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.