Exclusive hadronic tau decays as probes of non-SM interactions

Abstract

We perform a global analysis of exclusive hadronic tau decays into one and two mesons using the low-energy limit of the Standard Model Effective Field Theory up to dimension six, assuming left-handedneutrinos. A controlled theoretical input on the Standard Model hadronic form factors, based on chiralsymmetry, dispersion relations, data and asymptotic QCD properties, has allowed us to set bounds on theNew Physics effective couplings using the present experimental data. Our results highlight the importanceof semileptonic τ decays in complementing the traditional low-energy probes, such nuclear β decays orsemileptonic pion and kaon decays, and the high-energy measurements at LHC scales. This makes yetanother reason for considering hadronic tau decays as golden modes at Belle-II.