W Boson

Charged mediator of the weak force, responsible for radioactive beta decay and flavor change.

Core Principles & Analysis

• Discovered at CERN's Super Proton Synchrotron in 1983 by the UA1 and UA2 experiments.
• Mediates beta decay by transforming a down quark into an up quark.
• CDF's anomalous 2022 mass measurement was countered by 2024 CMS results agreeing with the Standard Model.

Specifications & Metrics

• MASS: 80.3625 ± 0.0077 GeV/c²
• SPIN: 1
• SYMBOL: W⁻ / W⁺
• DECAY WIDTH: 2.14 ± 0.05 GeV
• PDG ID: S043
• PDG EDITION: PDG 2026
• CHARGE: ±1 e

Principal Decay Modes

• W+ → lepton+ nu — 10.86 ± 0.09%
• W+ → e+ nu — 10.71 ± 0.16%
• W+ → mu+ nu — 10.63 ± 0.15%
• W+ → tau+ nu — 11.38 ± 0.21%
• W+ → hadrons — 67.41 ± 0.27%

Branching fractions: Particle Data Group, 2026 edition (CC BY 4.0).

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