New physics contributions in B → πτν and B → τν

We study possible new physics contributions in B → πτν and B → τν employing the model-independent effective Lagrangian that describes the quark-level transition b → uτν at low energies. The decay rate of B → πτν and its theoretical uncertainty are evaluated using the B → π form factors given by recent lattice QCD studies. Comparing theoretical results with the current experimental data, B(B → πτν) < 2.5 × 10-4 and B(B → τντ) = (1.14±0.22) × 10-4, we obtain constraints on the Wilson coefficients that quantify potential new physics. We also present the expected sensitivity of the SuperKEKB/Belle II experiment. © The Author(s) 2017. Published by Oxford University Press on behalf of the Physical Society of Japan1211Nsciescopu