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

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 $2.4\times 10^6$ ${\pi }^0\to e^{+}{e}^{-}\gamma$ 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.

arXiv comment14 pages, 11 figures

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