The baryon (quark content

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Symmetry, groups and the quark model · Electroweak theory and the Standard Model

Particle Physics, Ch The Standard Model as a table you can predict from

Problem

The Σ+\Sigma^+ baryon (quark content uusuus, mass 1189.37 MeV/c21189.37\,\mathrm{MeV}/c^2, strangeness S=−1S=-1) can, on energy grounds, decay to pπ0p\pi^0 (proton 938.272 MeV/c2938.272\,\mathrm{MeV}/c^2, neutral pion 134.98 MeV/c2134.98\,\mathrm{MeV}/c^2, both S=0S=0). ((a)) Using the four questions, decide which interaction must supply the vertex for Σ+→pπ0\Sigma^+ \to p\pi^0, given that both the initial and final states are ordinary hadrons made of u,d,su,d,s quarks. ((b)) Commit to an order-of-magnitude lifetime band for the Σ+\Sigma^+, before looking up the measured value, by comparison with another strange baryon already met, the Λ0\Lambda^0 (2.6×10−10 s2.6\times10^{-10}\,\mathrm{s}). ((c)) The measured lifetime of the Σ+\Sigma^+ is τ=0.8018×10−10 s\tau = 0.8018\times10^{-10}\,\mathrm{s}. Check the prediction against this value.

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