Precision measurement of the $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ Dalitz plot distribution with the KLOE detector

Abstract

Using $1.6$ fb${}^{-1}$ of $e^{+}{e}^{-}\to \ddot{I}•\to \hat{I}\cdot {\hat{I}}^3$ data collected with the KLOE detector at DA$\hat{I}¦$NE, the Dalitz plot distribution for the $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ decay is studied with the world's largest sample of $\sim 4.7\cdot 10^6$ 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 $g{X}^{2}Y$ term. The statistical uncertainty of all parameters is improved by a factor two with respect to earlier measurements.

11 pages, 9 figures, supplement: an ascii table