Just over two-thirds of the time, a $W$ boson decays into quarks, usually an up quark and a down antiquark... Right?
Since quarks hate being alone, what happens next?
Does the up quark pull a single other quark (or, rather, antiquark) from the 'sea' and become a meson, that then decays?
And, then, the down antiquark does the same thing?
Is there any chance a proton or neutron is created?