Description
The first run of the Belle II experiment collected a 365 fb$^{-1}$ sample of $e^+ e^-\to B\bar{B}$ collisions at a centre-of-mass energy corresponding to the $\Upsilon(4S)$ resonance. These data, with low particle multiplicity, constrained initial state kinematics and excellent lepton identification, are an ideal environment to study lepton-flavour universality in semileptonic decays of the $B$ meson.
We present results on the ratios of semitauonic decay rates compared to those to light leptons in both exclusive and inclusive $B$ decay. These include new measurements of the ratios for exclusive $B\to D^{(*)}\ell \nu$ decays $R(D^{(*)})$ in events tagged by a semileptonic $B$ decay.
Author
Steven Robertson
(IPP / University of Alberta)
