Measurement of $B^+\to \tau^+\nu_\tau$ branching fraction with a hadronic tagging method at Belle II

Sumitted to PubDB: 2026-04-08

Category: Phd Thesis

Tags:

Principal Authors	Giovanni Gaudino
Date	2026-02-18
Belle II Number	BELLE2-PTHESIS-2026-003
Abstract	I present a measurement of the branching fraction of $B^+ \to \tau^+ \nu_\tau$ decays using $(387 \pm 6)\times10^6~\Upsilon(4S)$ events collected between 2019 and 2022 with the Belle II detector at the SuperKEKB $e^+e^-$ collider. We reconstruct the accompanying $B^-$ meson using the hadronic tagging method, while $B^+ \to \tau^+ \nu_\tau$ candidates are identified in the recoil. We find evidence for $B^+ \to \tau^+ \nu_\tau$ decays at 3.0 standard deviations, including systematic uncertainties. The measured branching fraction is $\mathcal{B}(B^+ \to \tau^+ \nu_\tau) = [1.24 \pm 0.41~(\mathrm{stat}) \pm 0.19~(\mathrm{syst})]\times10^{-4}$.
Institute	Napoli