= Down quark
{title2=$d$}
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The down quark $d$ is the first-generation down-type <quark>, with <electric charge> $-e/3$, <spin> $1/2$ and <baryon number> $1/3$. Together with the <up quark>, it supplies the net valence flavor content of ordinary <protons> and <neutrons>.<Quark Model in the 2024 Review of Particle Physics>[§15.2 and Table 15.1]{ref}
The minimal neutron content $udd$ has total <electric charge> zero and <baryon number> one. In <beta decay>, a down-to-up <weak charged current> can turn a <neutron> into a <proton>, accompanied by the required leptons. This is a flavor change, rather than an electron previously stored inside the neutron escaping. Additional quark pairs and <gluons> are part of the full hadron state.
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