Parity Doublets in Quark Physics
A. P. Balachandran, Sachindeo Vaidya · Physical Review Letters · 1997
There are numerous examples of very nearly degenerate states of opposite parity in molecular physics. The ammonia maser is based on one such doublet. Theory shows that these parity doublets can occur if the nuclear shape in the molecule is reflection asymmetric because the time scales of the shape and the electronic cloud are well separated. Parity doublets occur in nuclear physics as well for odd $A\ensuremath{\sim}219--229$. We discuss the theoretical foundation of these doublets and on that basis suggest that parity doublets should occur in particle physics too. In particular they should occur among baryons composed of $\mathrm{cbu}$ and $\mathrm{cbd}$ quarks.