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Baryons are made of three quarks, in the form $\vert qqq \rangle$. If we consider just the isospin doublet $u$ and $d$, there are 8 total possibilities:

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Now, the first 4 are respectively $\Delta^{++}, \Delta^+, \Delta^0$ and $ \Delta^-$. But what about the other 4?

Qmechanic
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ric.san
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1 Answers1

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  1. In OP's table the first 4 rows (=the isospin quadruplet) are the $\Delta$ particles, which sit inside a spin-$3/2$ $uds$ baryon decuplet.

  2. The 4th and 3rd last rows are the proton and neutron, respectively, which form an isospin duplet, and which sit inside a spin-$1/2$ $uds$ baryon octet.

  3. The last 2 rows (=the second isospin duplet) are absent in the standard model, cf. e.g. this related Phys.SE post.

Qmechanic
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