= Up quark
{title2=$u$}
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The up quark $u$ is the first-generation up-type <quark>, with <electric charge> $+2e/3$, <spin> $1/2$ and <baryon number> $1/3$. It is a light quark, and the <up quark> and <down quark> together account for the net valence flavor content of ordinary nuclei.<Quark Model in the 2024 Review of Particle Physics>[§15.2 and Table 15.1]{ref}
The minimal <proton> content $uud$ has total charge $2(2e/3)-e/3=e$ and <baryon number> one. The proton's <mass> is not simply the sum of three free-quark masses: its interacting quark and <gluon> fields carry most of its <energy>. The <quark model> organizes the flavor content, while <quantum chromodynamics> describes the dynamics needed to compute hadron properties.
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