An antiquark is the antiparticle of a quark, with opposite electric charge, baryon number and additive flavor numbers, the same mass and spin, and the conjugate color representation. Thus an anti-up quark has charge , whereas an anti-down quark has charge .
A quark–antiquark pair can have zero net baryon number and combine into a color singlet, supplying the minimal valence content of a meson. Flavor cancellation is separate from electric-charge cancellation: has baryon number zero but electric charge . Antiquarks also occur in the nonvalence partonic content of hadrons, so their presence does not imply that the entire hadron is an antimatter counterpart of another one.
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