New paper “Irreducible Bhabha background in the detection of muonium-antimuonium conversion” [arXiv:2510.25828]

Published a new paper with FSU theory colleagues: Prof. Takemichi Okui, Mitrajyoti Ghosh (postdoc), and Kevin Liguori (Okui’s student).
[arXiv:2510.25828] Phys.Rev.D 113 (2026) 056014

Experiments such as MACS and the proposed MACE look for muonium-antimuonium conversion using the energies of the final-state electron and positron. In this paper, we point out that the electron and positron can exchange their energies by hard Bhabha scattering, so that a muonium decay fakes an antimuonium decay signal.

1. Compute the rate of this background.
2. It is negligible for MACE, but becomes larger than the signal for conversion probabilities below 10^-18.
3. Measuring the helicity of the electron reduces this to 10^-22.