Particle Physics - FSU Physics Department

color charge
problem with quark model
• Quarks have spin ½, i.e. are fermions ⇒ must obey Pauli
principle
• Ω - = sss, has spin 3/2; spins of 3 s quarks must be
aligned, i.e. Ω - has 3 quarks in identical state ---
forbidden
• similarly for Δ ++ = uuu, spin 3/2
way out: quarks have additional hidden property – “color
charge”
• 3 colors: green, red, blue
• each quark can carry one of three colors
o red blue green
• antiquarks carry anticolor
o anti-red anti-blue anti-green
• observed particles are “color-neutral”;
• only colorless (“white”) combinations of
quarks and antiquarks can form particles:
• qqq
• qq
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