Observation of overlapping spin-1 and spin-3 ${\bar{D}}^0{K}^{-}$ resonances at mass $2.86\mathrm{GeV}/c^2$

Abstract

The resonant substructure of $B_s^0\to {\bar{D}}^0{K}^{-}\ddot{I}{€}^{+}$ decays is studied using a data sample corresponding to an integrated luminosity of $3.0{\mathrm{fb}}^{-1}$ of $pp$ collision data recorded by the LHCb detector. An excess at $m({\bar{D}}^0{K}^{-})\approx 2.86\mathrm{GeV}/c^2$ is found to be an admixture of spin-1 and spin-3 resonances. Therefore the $D_{sJ}^{\ast }(2860{)}^{-}$ state previously observed in inclusive $e^{+}{e}^{-}\to {\bar{D}}^0{K}^{-}X$ and $pp\to {\bar{D}}^0{K}^{-}X$ processes consists of at least two particles. This is the first observation of a heavy flavoured spin-3 resonance, and the first time that any spin-3 particle has been seen to be produced in $B$ decays. The masses and widths of the new states and of the $D_{s2}^{\ast }(2573{)}^{-}$ meson are measured, giving the most precise determinations to date.

10 pages, 4 figures; updated for publication