  Upcoming fixed-target experiments designed to search for new sub-GeV forces
will also have sensitivity to the never before observed True Muonium atom, a
bound state of a muon and anti-muon. We describe the production and decay
characteristics of True Muonium relevant to these experiments. Importantly, we
find that secondary production mechanisms dominate over primary production for
the long-lived 2S and 2P states, leading to total yields an order of magnitude
larger than naive estimates previously suggested. We present yield estimates
for True Muonium as a function of energy fraction and decay length, useful for
guiding future experimental studies. Discovery and measurement prospects appear
very favorable.
