New high-statistics measurement of the $\ddot{I}{€}^0\to e^{+}{e}^{-}{\hat{I}}^3$ Dalitz decay at the Mainz Microtron

Abstract

The Dalitz decay $\ddot{I}{€}^0\to e^{+}{e}^{-}{\hat{I}}^3$ has been measured with the highest statistical accuracy obtained so far in the ${\hat{I}}^{3}p\to \ddot{I}{€}^{0}p$ reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value of the slope parameter for the $\ddot{I}{€}^0$ electromagnetic transition form factor, $a_{\ddot{I}}€=0.0315\pm 0.0026_{\mathrm{stat}}\pm 0.0010_{\mathrm{syst}}$, is obtained from the analysis of $2.4\times 10^6$ $\ddot{I}{€}^0\to e^{+}{e}^{-}{\hat{I}}^3$ observed decays. Within experimental uncertainties, it is in agreement with existing measurements and theoretical calculations, with its own uncertainty being smaller than previous results based on the analysis of $\ddot{I}{€}^0\to e^{+}{e}^{-}{\hat{I}}^3$ decays.

14 pages, 11 figures