Precision tau physics: Challenge for Theory, on and off the lattice

Abstract

$\tau$ is playing an important role in the current B-physics indications from experiments of lepton flavor universality violations(LFUV). This suggests it be given increasing attention theoretically in the coming years, given also the fact that Belle-II will have much larger data samples to study; similar comments also apply to LHCb as well as ATLAS and CMS. The fact that $\tau$ decays provide valuable information on its spin is an added advantage. This gains special significance if the current indications of new physics are upheld since naturalness arguments then strongly suggest that new physics should be accompanied by new CP-odd phase(s). Moreover, the fact that the $\tau$ mass is around 1.8 GeV,~{\it i.e} a lot less than the B-meson mass makes it much easier candidate for lattice studies in great detail and consequently very likely with greater precision. This should help us test the SM and or BSMs with greater precision as needed.