The charm quark is the second-generation up-type quark, with electric charge , spin and baryon number . It is heavier than the strange quark and is commonly treated as a heavy quark.[ref]
A charm–charm antiquark pair supplies the minimal valence content of charmonium, while a charm quark bound with a light antiquark gives an open-charm meson. These systems probe different aspects of quantum chromodynamics: internal heavy-pair motion in the former and heavy–light dynamics in the latter. The approximate flavor classification that includes charm does not make charm and the light quarks equal in mass.
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