Complementarity of μTRISTAN and Belle II in searches for charged-lepton flavour violation

Abstract

We analyse the potential of the proposed μ+μ+ and μ+e− collider μTRISTAN to complement the searches for charged-lepton flavour-violation (CLFV) that can be carried out by Belle II. μTRISTAN offers the possibility of directly producing and studying new resonances that could mediate CLFV for a certain range of masses. In addition, we find that it can produce competitive bounds to those from Belle II for cases where the new resonance lies beyond direct reach. We illustrate these points with three Z3 “lepton triality” models, where we also find an example that can only be probed by μTRISTAN. These three models feature doubly-charged scalars, denoted k1,2,3 respectively, that induce both CLFV and..