Neutrons and protons are spin-1/2 fermions and baryons

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It turns out that calling protons and neutrons "triquarks" is a little dangerous, as there are combinations of 3 quarks that describe particles that are not just spin-1/2, so intermediate abstract blocks have been introduced: SpinHalfBaryon extends TriQuarkBaryon, with the editorial stereotype «?» applied to the Generalization, because it is not yet clear whether every SpinHalfBaryon is made of three quarks.

Anybody thinking of pentaquarks?

UML/SysML is able to handle the multiplicities of the valence quarks nicely, where valenceQuark:Quark is a subset of quark:Quark (as the snippets imply that somehow 'valence quarks' are special).

(Later, we'll learn that protons and neutrons are both nucleons, but since no treated snippets mention that yet it is not included yet.)

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