Someone argues: "The baryon octet diagram shows only one point at

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

Particle Physics, Ch SU(3) flavour and the hadron multiplets

Problem

(I_3,Y)=(0,0)

, so the

\Sigma^0

and

\Lambda

baryons, which both have quark content

uds

and both sit there, must be the same particle observed under two names." ((a)) State the measured masses of

\Sigma^0

(

1192.6\,\mathrm{MeV}/c^2

) and

\Lambda

(

1115.7\,\mathrm{MeV}/c^2

) and their difference. ((b)) Explain, using isospin, how two distinct particles can occupy the same point on the

(I_3,Y)

plane. ((c)) Identify the error in the quoted argument.

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