By considering representations of SU(3), a 1971 paper by Gross and Wilczek predicted that there can be at most 16 of these properties for QCD to be asymptotically free. For 10 points each:
[10e] Name these properties that distinguish different varieties of quarks.
ANSWER: flavors
[10m] The same result demonstrated that there could be at most 2 fermions that are these representations of SU(3). Mesons containing only up, down, or strange quarks form this adjoint representation of SU(3).
ANSWER: octets [accept eight; accept eightfold way]
[10h] At low energies, QCD has a chirally broken approximate SU(2) symmetry, whose pseudo-Nambu–Goldstone modes are these particles, explaining their low mass.
ANSWER: pions
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