09-17-2021-0006 - charm isospin lepton electric charge X quantum

 Charm (symbol C) is a flavour quantum number representing the difference between the number of charm quarks (

c
) and charm antiquarks (
c
) that are present in a particle:

By convention, the sign of flavour quantum numbers agree with the sign of the electric chargecarried by the quarks of corresponding flavour. The charm quark, which carries an electric charge (Q) of +2⁄3, therefore carries a charm of +1. The charm antiquarks have the opposite charge(Q = −2⁄3), and flavour quantum numbers (C = −1).

As with any flavour-related quantum numbers, charm is preserved under strong and electromagnetic interaction, but not under weak interaction (see CKM matrix). For first-order weak decays, that is processes involving only one quark decay, charm can only vary by 1 (ΔC= ±1,0). Since first-order processes are more common than second-order processes (involving two quark decays), this can be used as an approximate "selection rule" for weak decays.

https://en.wikipedia.org/wiki/Charm_(quantum_number)

https://en.wikipedia.org/wiki/Isospin

https://en.wikipedia.org/wiki/Weak_isospin

https://en.wikipedia.org/wiki/Lepton_number

https://en.wikipedia.org/wiki/Electric_charge

https://en.wikipedia.org/wiki/X_(charge)

https://en.wikipedia.org/wiki/Hypercharge

https://en.wikipedia.org/wiki/Baryon_number

https://en.wikipedia.org/wiki/Weak_hypercharge