Strange Particle

strange particle [′strānj ′pard·ə·kəl]

(particle physics)

A hadron whose strangeness number is not zero, for example, aK-meson or a Σ-hyperon.

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Strange Particle 

a hadron—that is, a strongly interacting particle—whose strangeness number 5 is not zero. By contrast, S = 0 for ordinary, or nonstrange particles (pions, protons, and neutrons). Kaons, hyperons, and some resonances are strange particles.

All strange particles are unstable. Strange resonances decay very rapidly through strong interactions and have lifetimes of the order of 10^–23 sec. Since strangeness is conserved in strong interactions, the total strangeness of the decay products is equal to the strangeness of the original particle. The other strange particles are quasi-stable and decay relatively slowly through weak interactions. The lifetimes of such particles are of the order of 10^–8–10^–10 sec. The decay products in this case may be leptons, nonstrange particles, or strange particles of lesser strangeness. The total strangeness of the decay products here differs from the strangeness of the original particle by 1.

Strange particles can be produced with high probability in collisions of ordinary hadrons. In this case, however, they must be produced in pairs (or in larger quantities) so that their total strangeness is equal to zero. Strange particles decay into ordinary particles with a very low probability. This “strangeness” in the behavior of the particles is the reason for their name.

A. A. KOMAR