New high-statistics measurement of the $\pi^0 \to e^+e^-\gamma$ Dalitz decay at the Mainz Microtron

TL;DR

This paper reports a high-statistics measurement of the $^0 o e^+e^- gamma$ decay, providing a precise determination of the transition form factor slope parameter, consistent with prior results and theory.

Contribution

It presents the most precise measurement to date of the $^0$ transition form factor slope parameter using a large dataset from the Mainz Microtron.

Findings

Measured the slope parameter $a_=0.0315\u00b1 0.0026_{ ext{stat}}.0010_{ ext{syst}}$

Analyzed $2.4 imes 10^6$ decay events

Results agree with previous measurements and theoretical predictions

Abstract

The Dalitz decay $\pi^0 \to e^+e^-\gamma$ has been measured with the highest statistical accuracy obtained so far in the $\gamma p\to \pi^0 p$ reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value of the slope parameter for the $\pi^0$ electromagnetic transition form factor, $a_\pi=0.0315\pm 0.0026_{\mathrm{stat}}\pm 0.0010_{\mathrm{syst}}$, is obtained from the analysis of $2.4\times10^6$ $\pi^0 \to e^+e^-\gamma$ 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 $\pi^0\to e^+e^-\gamma$ decays.