Which of the following processes are allowed by the strong...

Which of the following processes are allowed by the strong interaction, the electromagnetic interaction, the weak interaction, or no interaction at all? (a) $\pi^{-}+\mathrm{p} \rightarrow 2 \eta$ (b) $\mathrm{K}^{-}+\mathrm{n} \rightarrow \Lambda^{0}+\pi^{-}$ (c) $\mathrm{K}^{-} \rightarrow \pi^{-}+\pi^{0}$ (d) $\Omega^{-} \rightarrow \Xi^{-}+\pi^{0}$ $(\mathrm{e}) \eta \rightarrow 2 \gamma$

Which of the following processes are allowed by the strong interaction, the electromagnetic interaction, the weak interaction, or no interaction at all?
(a) $\pi^{-}+\mathrm{p} \rightarrow 2 \eta$
(b) $\mathrm{K}^{-}+\mathrm{n} \rightarrow \Lambda^{0}+\pi^{-}$
(c) $\mathrm{K}^{-} \rightarrow \pi^{-}+\pi^{0}$
(d) $\Omega^{-} \rightarrow \Xi^{-}+\pi^{0}$
$(\mathrm{e}) \eta \rightarrow 2 \gamma$

Key Concepts

Strong Interaction

The strong force is the fundamental interaction responsible for binding quarks into hadrons and for holding the nucleus together. It is characterized by rapid, short-range interactions that conserve quantum numbers such as baryon number, isospin, and strangeness. Because of its high coupling strength, processes mediated by the strong interaction occur very quickly, and any violation of its conserved quantum numbers typically points to another interaction type.

Electromagnetic Interaction

The electromagnetic force acts on charged particles and is mediated by photons. It obeys conservation laws such as electric charge conservation and often governs processes that involve the emission or absorption of electromagnetic radiation. Although generally weaker than the strong interaction, its long-range nature allows it to play a key role in decays and scattering events where changes are mediated by photon exchange.

Weak Interaction

The weak interaction is responsible for processes in which particles change flavor, such as certain decays that cannot proceed via the strong or electromagnetic forces. It is characterized by its relatively low coupling strength and longer timescales compared to the strong interaction, and it permits violations of conservation laws (like strangeness) that are otherwise conserved in strong and electromagnetic processes. Additionally, the weak force is unique in its violation of parity symmetry.

Conservation Laws in Particle Physics

In analyzing particle interactions and decays, conservation laws play a critical role in determining which processes are allowed. These laws include, but are not limited to, conservation of energy, momentum, electric charge, baryon number, and lepton number. Specific interactions also impose additional conservation rules, such as the conservation of strangeness in strong and electromagnetic interactions, which provide important criteria for identifying the underlying interaction responsible for a given process.

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