Importance of the Breit interaction for electron-positron pair production in bound-bound muon transitions

We explored a distinct mechanism for matter creation via electron-positron pair production during bound-bound transitions in the deexcitation of muonic atoms. For ions with nuclear charges Z ≥ 24, transitions from low-lying excited states to the 1s-muon state can lead to the production of electronpositron pairs. We show that the Breit interaction determines the transition probabilities for states with nonzero orbital momentum. We show that the pair production arises mainly from the decay of the 2p states. Thus, the Breit interaction governs electron-positron pair production in bound-bound muon transitions. This process offers a unique opportunity to explore quantum electrodynamics in strong fields, as well as a class of nonradiative transitions involving electron-positron pair production.