= Radiative Sigma-to-Lambda transition
{title2=$\Sigma^0\to\Lambda^0\gamma$}
The neutral <Sigma baryon> and <Lambda baryon> both have valence content $uds$, but different spin-isospin couplings. An electromagnetic transition changes those internal couplings without changing any quark flavour. In the simple ground-state quark model, the nonzero magnetic transition is associated with the up- and down-quark electromagnetic currents; the strange-quark spin operator alone cannot change the $ud$ pair from spin one to spin zero. <Four-momentum conservation> gives photon energy $E_\gamma=(M_\Sigma^2-M_\Lambda^2)/(2M_\Sigma)$ in <natural units>.
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