# Portorož 2017: New physics at the junction of flavor and collider phenomenology

Apr 18 – 21, 2017
Europe/Zurich timezone

## Tau polarizations in $B\to D\tau\nu$ decays from final-state kinematics

Apr 19, 2017, 3:39 PM
23m
Plenary talk

### Speaker

Susanne Westhoff (Heidelberg University)

### 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.