Prospects for observing the lowest-lying odd-parity Sigma_c and Sigma_b baryons

There exist candidates for the negative-parity states $\Lambda_{c,b}(1/2^-, 3/2^-)$ consisting of an isospin-zero, spin-zero light diquark $[ud]$ with one unit of orbital angular momentum with respect to a $c,b$ quark. However, there exists only one candidate for the orbital excitations of the $\Sigma_c(1/2^+)$ and $\Sigma_c^*(3/2^+)$, and none for the orbital excitations of $\Sigma_b(1/2^+)$ or $\Sigma_b^*(3/2^+)$. We extend a previous discussion of odd-parity $\Lambda_{c,b}$ states and explore some patterns of the odd-parity $\Sigma_{c,b}$ baryons consisting of a light isospin-one nonstrange diquark $(uu,ud,dd)$ in a state of $L=1$ with respect to the spin-1/2 heavy quark $(c,b)$.