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

TL;DR

This study measures Dalitz decays of eta and omega mesons using the A2 setup at MAMI, providing precise transition form factor parameters that align well with theoretical models and improve upon previous experimental uncertainties.

Contribution

The paper presents new measurements of the eta and omega transition form factors with reduced uncertainties, enhancing the understanding of meson electromagnetic structure.

Findings

Eta transition form factor slope parameter Lambda^{-2}_eta = 1.97±0.11 GeV^{-2}

Omega transition form factor slope parameter Lambda^{-2}_omega_pi^0 = 1.99±0.21 GeV^{-2}

Results agree with theoretical calculations and improve precision over previous measurements.

Abstract

The Dalitz decays eta -> e^+e^-g and omega -> pi^0 e^+e^- have been measured in the g p -> eta p and g p -> omega p 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 eta, Lambda^{-2}_eta=(1.97+/-0.11_tot) GeV^{-2}, is in good agreement with previous measurements of the eta -> e^+e^-g and eta -> mu^+mu^-g decays. The uncertainty obtained in the value of Lambda^{-2}_eta is lower than in previous results based on the eta -> e^+e^-g decay. The value obtained for the omega slope parameter, Lambda^{-2}_omega_pi^0 = (1.99+/-0.21_tot) GeV^{-2}, is somewhat lower than previous measurements based on omega -> pi^0 mu^+mu^-, but the results for the omega transition form factor are in better agreement with theoretical calculations, compared to earlier experiments.