The baryon (quark content ) is observed to decay as

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Particles, interactions and experiment

Particle Physics, Ch Quantum numbers, conservation laws and allowed reactions

Problem

The baryon

\Xi^-

(quark content

dss

) is observed to decay as

\Xi^- \to \Lambda + \pi^-

, with a measured mean lifetime of

1.639\times10^{-10}\,\mathrm{s}

. The

\Lambda

has quark content

uds

and the

\pi^-

d\bar u

. ((a)) Find the strangeness of

\Xi^-

\Lambda

and

\pi^-

from their quark content, and hence

\Delta S

for the decay. ((b)) Using

\Delta S

and the measured lifetime, state which interaction is responsible for this decay.

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