Speaker
Description
BABAR, Belle, and LHCb measure the rates for the decays $B \to D^{(*)} \tau \nu$ and $B_c\to J/\psi \tau \nu$ to be higher than the SM expectations, with a combined discrepancy of $4.1 \sigma$ (for $B \to D^{(*)} \tau \nu$ only) or $\sim 4.3 \sigma$ (including all modes). In the coming years, Belle II and LHCb will greatly improve the measurement precision, to the level that systematic uncertainties associated with the background $B \to D^{**} \ell \nu$ become critical. We show how to utilize Belle II's high spatial resolution to obtain a model-independent handle on this background and improve the overall signal-backgroud. We also study the impact of vertexing on Belle II’s capability to perform this measurement with the decay $\tau \to 3 \pi \nu$, as already demonstrated by LHCb.
