= Quark Model in the 2024 Review of Particle Physics
{c}
{title2=2024}
Official review: https://pdg.lbl.gov/2024/reviews/rpp2024-rev-quark-model.pdf
Section 15.3 discusses <mesons>; section 15.5.2, printed p. 19, explains that adding the <charm quark> gives flavour $SU(4)$, which is strongly broken by the large <charm quark> <mass> but remains useful for classification. This supports distinguishing an approximate flavour symmetry from the existence of a four-flavour <quark model>.
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