1. What are Hyperons?
Hyperons are a class of baryons that contain one or more strange quarks (s). They are heavier than nucleons (proton and neutron) and are produced mainly in high-energy particle interactions.
2. Quark Composition
Like all baryons, hyperons consist of three quarks. The presence of at least one strange quark distinguishes them from nucleons.
| Hyperon | Symbol | Quark Content | Charge |
|---|---|---|---|
| Lambda | Λ⁰ | uds | 0 |
| Sigma | Σ⁺, Σ⁰, Σ⁻ | uus, uds, dds | +1, 0, −1 |
| Xi (Cascade) | Ξ⁰, Ξ⁻ | uss, dss | 0, −1 |
| Omega | Ω⁻ | sss | −1 |
3. Strangeness Quantum Number
Hyperons possess a non-zero strangeness (S) quantum number. Each strange quark contributes:
• s quark → S = −1
• s̄ antiquark → S = +1
Example:
Λ⁰ (uds) → S = −1
Ω⁻ (sss) → S = −3
4. Properties of Hyperons
| Property | Description |
|---|---|
| Baryon Number | +1 |
| Spin | 1/2 or 3/2 |
| Mass | Greater than nucleons |
| Lifetime | ~10⁻¹⁰ seconds |
| Stability | Unstable |
5. Decay of Hyperons
Hyperons decay via the weak interaction because strangeness is conserved in strong interactions but not in weak interactions.
Λ⁰ → p + π⁻
The relatively long lifetime of hyperons compared to strongly decaying particles is a key experimental signature of weak decay.
6. Classification of Hyperons
- Lambda (Λ) – isospin 0
- Sigma (Σ) – isospin 1
- Xi (Ξ) – double strange baryons
- Omega (Ω) – triple strange baryon
7. Importance of Hyperons
The study of hyperons has played a crucial role in:
- Discovery of the strange quark
- Development of the quark model
- Understanding weak interactions
- Exploring dense nuclear matter (neutron stars)
8. Key Points for Exams
🔹 All hyperons are baryons
🔹 Hyperons decay via weak interaction
🔹 Ω⁻ discovery confirmed quark model predictions