Search for lepton-flavor-violating $\tau$ decays into a lepton and a vector meson using the full Belle data sample

Charged-lepton-flavor-violation is predicted in several new physics scenarios. We update the analysis of $\tau$ lepton decays into a light charged lepton ($\mathrm{\ell }$ = $e^{\pm }$ or ${\mu }^{\pm }$) and a vector meson ($V^0$ = ${\rho }^0$, $\phi$, $\omega$, $K^{\ast 0}$, or $\bar{K}{}^{\ast 0}$) using 980 fb${}^{-1}$ of data collected with the Belle detector at the KEKB collider. No significant excess of such signal events is observed, and thus 90% credibility level upper limits are set on the $\tau \to \mathrm{\ell }{V}^0$ branching fractions in the range of (1.7–$4.3)\times {10}^{-8}$. These limits are improved by 30% on average from the previous results.