Search for B^{-}→μ^{-}ν[over ¯]_{μ} Decays at the Belle Experiment.

Area of Science:

• Particle Physics
• High-Energy Physics
• Experimental Physics

Background:

• The Standard Model of particle physics predicts rare B meson decays.
• Understanding these decays provides insights into fundamental interactions.
• Previous searches for B meson leptonic decays have yielded limited results.

Purpose of the Study:

• To search for the purely leptonic decay of the B meson into a muon and neutrino (B⁻→μ⁻ν[over ¯]μ).
• To measure the branching fraction of this rare decay.
• To test predictions of the Standard Model.

Main Methods:

• Analysis of a large dataset (711 fb⁻¹) collected by the Belle detector at the KEKB collider.
• Selection of signal events based on high momentum muons and event topology.
• Reconstruction of missing energy and momentum to identify neutrino presence.

Main Results:

• Observed a 2.4 standard deviation excess above background.
• Measured branching fraction B(B⁻→μ⁻ν[over ¯]μ) = (6.46 ± 2.22 ± 1.60) × 10⁻⁷.
• Determined a 90% confidence level interval for the branching fraction of [2.9, 10.7] × 10⁻⁷.

Conclusions:

• The results provide evidence for the rare B⁻→μ⁻ν[over ¯]μ decay.
• The measured branching fraction is consistent with Standard Model predictions.
• This search contributes to the precise measurement of fundamental parameters in particle physics.