Speaker
Description
Recent improvements of the Large Hadron Collider luminosity and the beginning of Belle II experiment will increase the sensitivity to tau lepton-flavour violating modes. In particular, it has been claimed by Pham in hep-ph/9810484 that $BR(\tau \to 3 \mu)$ could be as large as $10^{−14}$ in the Standard Model with massive neutrinos, contradicting earlier predictions for $BR(\mu \to 3e)$. If this were to be true, this limit could be reached experimentally in the near future (with further upgrades).
In this talk, we present a new calculation of these branching ratios in full generality within the Standard Model including massive neutrinos. By making use of the method of regions, we determine the rates as a double expansion in $m_\nu/m_\tau$ and $m_\tau/M_W$. We also report some discrepancies with previous predictions.
