Explaining lepton-flavor non-universality and self-interacting dark matter with L_mu -L_tau

Abstract

Experimental hints for lepton-flavor universality violation in the muon’s magnetic moment as well as neutral- and charged-current B-meson decays require Standard-Model extensions by particles such as leptoquarks that generically lead to unacceptably fast rates of charged lepton flavor violation and proton decay. We propose a model based on a gauged U(1)_{L_mu -L_tau } that eliminates all these unwanted decays by symmetry rather than finetuning and efficiently explains (g-2)_mu , R_{K^{(*)}}, R_{D^{(*)}}, and neutrino masses. The U(1)_{L_mu -L_tau } furthermore acts as a stabilizing symmetry for dark matter and the light Z' gauge boson mediates velocity-dependent dark-matter self-interactions that resolve the small-scale structure problems. Lastly, even the Hubble tension can be ameliorated via the light Z' contribution to the relativistic degrees of freedom.