# W Boson Decay

#### Ajihood

Hey Guys,

Just a quick question. Can a W boson decay to a u and anti s or does it have to decay to a quark and anti-quark of the same generation?

Thanks!

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#### fzero

The weak couplings are determined by the CKM matrix, which mixes the down type quarks between generations. So the $$W^+$$ can decay to $$u\bar{d}$$, $$u\bar{s}$$, $$u\bar{b}$$, as well as the corresponding channels involving the charm quark.