Chiral multiplets of heavy-light mesons

The recent discovery of a narrow resonance in $D_s{\pi }^0$ by the BaBar Collaboration is consistent with the interpretation of a heavy $J^P{(0\mathrm{}}^{+}{,1\mathrm{}}^{+})$ spin multiplet. This system is the parity partner of the ground state ${(0\mathrm{}}^{-}{,1\mathrm{}}^{-})$ multiplet, which we argue is required in the implementation of ${\mathrm{SU}\left(3\right)\mathrm{}}_L\times {\mathrm{SU}\left(3\right)\mathrm{}}_R$ chiral symmetry in heavy-light meson systems. The ${(0\mathrm{}}^{+}{,1\mathrm{}}^{+})\to {(0\mathrm{}}^{-}{,1\mathrm{}}^{-})+\pi$ transition couplings satisfy a Goldberger-Treiman relation, $g_{\pi }=\Delta {M/f}_{\pi },$ where $\Delta M$ is the mass gap. The BaBar resonance fits the $0^{+}$ state, with a kinematically blocked principal decay mode to $D+K.\mathrm{}$ The allowed $D_s+\pi ,$ $D_s+2\mathrm{}\pi ,$ and electromagnetic transitions are computed from the full chiral theory and found to be suppressed, consistent with the narrowness of the state. This state establishes the chiral mass difference for all such heavy-quark chiral multiplets, and precise predictions exist for the analogous $B_s$ and strange doubly heavy baryon states.