Distinguishing charged lepton flavor violation scenarios with inelastic µ → e conversion*

The forthcoming Mu2e and COMET experiments will search for electrons produced via the neutrinoless conversion of muons captured onto the atomic nucleus ^27­Al, improving existing limits on charged lepton flavor violation (CLFV) by roughly four orders of magnitude and probing new physics at scales in excess of 10,000 TeV. If a positive signal is observed, additional information will be required in order to determine the precise nature of the new physics responsible. Further constraints can be obtained by varying the nuclear target, requiring a series of experimental campaigns.  Conventionally,  conversion experiments are optimized to detect electrons originating in transitions where the nucleus remains in the ground state. We demonstrate that inelastic transitions to low-lying nuclear excited states can modify the near-endpoint spectrum of conversion electrons, providing complementary constraints on the underlying CLFV operators and potentially enabling experimentalists to distinguish between new physics scenarios using a single nuclear target.