True muonium resonant production at e + e − colliders with standard crossing angle

Abstract True muonium (TM) ( μ + μ − ) is the heaviest and smallest bound state not containing hadrons, after TM ( τ + τ − ) and mu-tauonium ( μ ± τ ∓ ). One of the proposed methods to observe the spin 1 fundamental state of TM, which has the smallest lifetime among TM spin 1 states, was to build an e + e − collider with a large crossing angle ( θ ∼ 30°) in order to provide TM with a large boost and detect its decay vertex in e + e − . The following paper will instead show that TM excited states can be observed in relatively large quantities ( O (10)/month) at a e + e − collider with standard crossing angle, after setting their center-of-mass energy to the TM mass (∼2 m μ = 211.4 MeV).