Measurement of the omega-> pi 0 e+ e-and eta-> e+ e-g Dalitz decays with the A2 setup at MAMI

The Dalitz decays η → e
+e
−γ and ω → π
0
e
+e
− have been measured in the γp → ηp and
γp → ωp reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron, MAMI.
The value obtained for the slope parameter of the electromagnetic transition form factor of η,
Λ
−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 Λ−2
η is lower than in previous
results based on the η → e
+e
−γ decay. The value obtained for the ω slope parameter, Λ−2
ωπ0 =
(1.99±0.21tot ) GeV−2
, is somewhat lower than previous measurements based on ω → π
0µ
+µ
−, but
the results for the ω transition form factor are in better agreement with theoretical calculations,
compared to earlier experiments.