Constraining Muon Internal Bremsstrahlung as a Contribution to the MiniBooNE Low Energy Excess

Using a cleanly tagged data sample of $ u_mu$ charged current events, it is demonstrated that the rate at which such events are mis-identified as $ u_e$s is accurately simulated in the MiniBooNE $ u_mu to u_e$ analysis. Such mis-identification, which could arise from muon internal bremsstrahlung, is decisively ruled out as a source of the low energy electron-like events reported in the MiniBooNE search for $ u_mu to u_e$ oscillations. This refutes the conclusions of a recent paper which postulates that hard bremsstrahlung could form a substantial background to the MiniBooNE $ u_e$ sample.