Abstract
An experimental study of the decay has been conducted with the best up-to-date statistical accuracy, by measuring mesons produced in the reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The results obtained for the standard parametrization of the matrix element are consistent with the most recent results for decays, but have smaller uncertainties. The available statistics and experimental resolution allowed, for the first time, an observation of a structure below the mass threshold, the magnitude and sign of which, checked within the framework of the nonrelativistic effective-field theory, demonstrated good agreement with the cusp that was predicted based on the scattering length combination, , extracted from decays.
1 More- Received 13 September 2017
DOI:https://doi.org/10.1103/PhysRevD.98.012001
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society