Study of the eta-->e+e-g Decay using WASA-at-COSY Detector System

TL;DR

This study analyzes the eta meson decay into an electron-positron pair and a photon using the WASA-at-COSY detector, providing insights into the meson's electromagnetic structure through the transition form factor.

Contribution

First measurement of the eta transition form factor and slope parameter using the eta-->e+e-g decay channel with the WASA-at-COSY detector.

Findings

Extraction of the eta transition form factor as a function of e+e- mass.

Calculation of the eta meson charge radius from the slope parameter.

Results contribute to understanding the electromagnetic structure of the eta meson.

Abstract

At the turn of October and November 2008, the WASA-at-COSY collaboration performed an experiment to collect data on the eta meson decays in pd-->3He eta reactions. This report presents results of a study of the eta-->e+e-g conversion decay. The desired feature of this decay is that the final state e+e- pairs come from the conversion of a virtual gamma quantum and, therefore, they constitute a rich source of knowledge about the electromagnetic structure of decaying meson. This is a very important characteristic when it comes to study of a short-lived neutral particle like the eta meson, because the classical methods of particle scattering are not applicable here. The analysis performed on one third of the p-d data sample collected using the WASA-at-COSY detector, lead to the extraction of the eta transition form factor as a function of the e+e- mass and to the calculation of the slope parameter, related to the charge radius of the eta meson.