The hyperon has 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^- hyperon has quark content ddsdds, mass 1197.45 MeV/c21197.45\,\mathrm{MeV}/c^2, baryon number B=1B=1 and strangeness S=−1S=-1. A candidate decay is Σ−→n π−\Sigma^- \to n\,\pi^-, where the neutron has mass 939.57 MeV/c2939.57\,\mathrm{MeV}/c^2 and strangeness S=0S=0, and the π−\pi^- has mass 139.57 MeV/c2139.57\,\mathrm{MeV}/c^2 and strangeness S=0S=0. ((a)) Check charge, baryon number and strangeness for Σ−→n π−\Sigma^- \to n\,\pi^-. State whether the strong or electromagnetic interaction can drive it, and if not, name the interaction and the quark-level vertex that does. ((b)) State what CPT invariance requires for the lifetime of the antiparticle Σˉ+\bar\Sigma^+ (quark content dˉdˉsˉ\bar d\bar d\bar s) compared with Σ−\Sigma^-. ((c)) Using the interaction identified in part (a), predict the order-of-magnitude band for the Σ−\Sigma^- lifetime, and compare it with the measured value τ=1.479×10−10 s\tau = 1.479\times10^{-10}\,\mathrm{s}.

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