Scouring meson decays for true muonium

TL;DR

This paper explores the potential to detect true muonium, a bound state of muons, through rare meson decays with branching ratios around 10^{-11}, analyzing specific decay channels and their experimental feasibility.

Contribution

It provides theoretical predictions for branching ratios of meson decays into true muonium and discusses experimental prospects for discovering this bound state.

Findings

Predicted branching ratios for $ ext{η'→(μ+μ−)γ}$ are around 4.8×10^{-10} and 3.7×10^{-11}.

Certain meson decay channels have branching ratios above 10^{-11}.

Discussion includes experimental detection prospects and background considerations.

Abstract

Rare meson decay experiments promise to measure branching ratios as small as $10^{-13}$. This presents an opportunity to discover the $\mu^+\mu^-$ bound state true muonium. We consider a set of possible channels, all with branching ratios above $\sim10^{-11}$. For the electromagnetic decays $\eta/\eta'\rightarrow(\mu^+\mu^-)\gamma$, theoretical and phenomenological form factors $F_{\eta/\eta'\gamma\gamma^*}(Q^2)$ allow predictions of $\mathcal{BR}(\eta'\rightarrow (\mu^+\mu^-) \gamma)\sim 4.8\times10^{-10}$ and $\mathcal{BR}(\eta'\rightarrow (\mu^+\mu^-) \gamma)\sim 3.7\times10^{-11}$ at the 5% level. Discussion of experimental prospects and potential backgrounds are made.