Speaker
Description
The semileptonic decays $B\to D^{(\ast)}\tau\nu$ have received lots of attention recently, due to an observed discrepancy between standard-model predictions and measurements. Experimentally, these processes are challenging due the fast decay of the tau lepton, which is indirectly observed through its decay products. From a theory perspective, the tau lepton is exactly what makes $B\to D^{(\ast)}\tau\nu$ decays interesting: The massive lepton offers the possibility to probe its polarization states individually and thereby learn about the details of its production process. I will show how to extract the tau polarizations from kinematics of the visible decay products in $\tau\to\pi\nu$, $\tau\to\rho\nu$, and $\tau\to\ell\nu\bar\nu$ decays. These new observables provide us with an analytical framework to fully explore the properties of $B\to D^{(\ast)}\tau\nu$ decays at BELLE II and LHCb.
