Here's something about for list members. In the Lepton sector all decays
conserved a kind of "family" number. That is we can define family lepton
number as L_1, L_2, L_3 one for each family. So we get
muon= electron + anti electron neutrino + muon neutrino
L_2 = L_1 -L_1 + L_2
Of course we know this global charge is not conserved in neutrino flavor
oscillations.
But in the quark sector we always get decays via the weak channel and there
is no family number to be conserved. So for example we do see
C= d + W(+)
But we never see
C= U + { dbar + s} = U+ K(0)bar
Which would, as in the lepton decay above, conserve a kind of quark
family number. Given that
M_c= 1100 Mev U= 4.2 Mev and K(0)bar= 497.7 Mev
There would seem to be no barrier to this decay channel. But we never see
it. Now quark masses are very tricky, so masses are really not pinned down
this well and actually the effective quark masses are much higher due the
balance between localization energy and the color force seeking a minimum
potential. Obviously the lack of this decay mode should relate to the
complexities of QCD. Any thought or comments on this?