Charm is the number of charm quarks (c) minus the number of charm anti-quarks (
) that are present in a particle:
This makes charm quark to have a charm of +1 and anti-charm quark to have a charm of −1 (the charm sign agreeing with the quark charge sign).
As with other flavor-related quantum numbers, charm is preserved under strong and electromagnetic interaction, but not under weak interaction. For firt-order weak reactions, it holds that | ΔC | = 1.
See also
