Lambda Baryon (Λ⁰)

First discovered hyperon: a three-quark baryon carrying a strange quark in place of a down quark.

Core Principles & Analysis

• Discovered in 1950 in cosmic-ray cloud-chamber photographs.
• Its up-down-strange composition made it a cornerstone of the quark-model classification.
• A Λ can replace a neutron inside a nucleus, forming exotic hypernuclei used to probe the strong force.

Specifications & Metrics

• SPIN: 1/2
• SYMBOL: Λ⁰
• CHARGE: 0 (neutral)
• MASS: 1115.683 ± 0.006 MeV/c²
• MEAN LIFE: 2.617 × 10⁻¹⁰ ± 1 × 10⁻¹² s
• PDG ID: S018
• PDG EDITION: PDG 2026

Principal Decay Modes

• Lambda → p pi- — 64.1 ± 0.5%
• Lambda → n pi0 — 35.9 ± 0.5%
• Lambda → n gamma — 0.083 ± 0.007%
• Lambda → p pi- gamma — 0.085 ± 0.014%
• Lambda → p e- nubar_e — 0.0834 ± 0.0014%

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

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