Flavor-changing light bosons with accidental longevity

Understand

We consider a model with a complex scalar field that couples to $(e,\mu)$ or $(\mu,\tau)$ within the "longevity" window: $[|m_{l_1} - m_{l_2}|, m_{l_1} + m_{l_2}]$ in which $l_1$ and $l_2$ are the two different charged leptons.

• Within such a mass window, even a relatively large coupling (e.g.
• of the size commensurate with the current accuracy/discrepancy in the muon $g-2$ experiment) leads to long lifetimes and macroscopic propagation distance between production and decay points.
• We propose to exploit several existing neutrino experiments and one future experiment to probe the parameter space of this model.