Measurement of the ω → π 0 e + e − and η → e + e − γ Dalitz decays with the A2 setup at the Mainz Microtron

Abstract

The Dalitz decays η → e+e−γ andω → π0e+e− have been measured in the γp → ηp and γp → ωp reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron. The value obtained for the slope parameter of the electromagnetic transition form factor of η, −2 η = (1.97 ± 0.11tot) GeV−2 , is in good agreement with previous measurements of the η → e+e−γ and η → μ+μ−γ decays. The uncertainty obtained in the value of −2 η is lower than in previous results based on the η → e+e−γ decay. The value obtained for the ω slope parameter, −2 ωπ0 = (1.99 ± 0.21tot) GeV−2 , is somewhat lower than previous measurements based on ω → π0μ+μ−, but the results for the ω transition form factor are in better agreement with theoretical calculations, compared to earlier experiments