Evidence for B- → τ- ν(τ) with a hadronic tagging method using the full data sample of Belle

Area of Science:

• Particle Physics
• High-Energy Physics
• Quantum Chromodynamics

Background:

• The B- meson system is a crucial laboratory for testing the Standard Model of particle physics.
• Understanding B-meson decays, particularly rare modes like B- → τ- ν(τ), provides insights into fundamental interactions and potential new physics.

Purpose of the Study:

• To measure the branching fraction of the B- → τ- ν(τ) decay.
• To search for evidence of this rare B-meson decay mode.

Main Methods:

• Analysis of a large dataset of 772×10^6 BB pairs collected by the Belle detector at the KEKB asymmetric-energy e+e- collider.
• Tagging of B-meson pairs by reconstructing one B meson into hadronic final states.
• Detection of B- → τ- ν(τ) candidates in the recoil of tagged B mesons.

Main Results:

• Evidence for the decay B- → τ- ν(τ) was found with a significance of 3.0 standard deviations.
• The branching fraction was measured as B(B- → τ- ν(τ)) = [0.72(-0.25)(+0.27)(stat) ± 0.11(syst)] × 10^-4.

Conclusions:

• The measurement provides evidence for the rare decay B- → τ- ν(τ).
• The obtained branching fraction can be used to constrain theoretical models and search for new physics beyond the Standard Model.