New physics contributions in $B\to\pi\tau\bar\nu$ and $B\to\tau\bar\nu$

TL;DR

This paper investigates potential new physics effects in specific B meson decays involving tau leptons using a model-independent approach, constraining new physics parameters with current data and projecting future experimental sensitivities.

Contribution

It provides a comprehensive analysis of new physics contributions in B to pi tau nu and B to tau nu decays using effective field theory and recent lattice QCD form factors, including current constraints and future prospects.

Findings

Constraints on Wilson coefficients from current data.

Predicted sensitivities for Belle II experiment.

Updated theoretical decay rate calculations.

Abstract

We study possible new physics contributions in $B\to\pi\tau\bar\nu $ and $B\to\tau\bar\nu$ employing the model-independent effective Lagrangian that describes the quark-level transition $b \to u \tau\nu$ at low energies. The decay rate of $B\to\pi\tau\bar\nu$ and its theoretical uncertainty are evaluated using the $B\to\pi$ form factors given by recent lattice QCD studies. Comparing theoretical results with the current experimental data, $\mathcal{B}(B\to\pi\tau\bar\nu)<2.5\times 10^{-4}$ and $\mathcal{B}(B\to\tau\bar\nu)=(1.14\pm 0.22)\times 10^{-4}$, we obtain constraints on the Wilson coefficients that quantify potential new physics. We also present the expected sensitivity of the SuperKEKB/Belle~II experiment.