Masses of Open-Flavour Heavy-Light Hybrids from QCD Sum-Rules

Abstract: We use QCD Laplace sum-rules to predict masses of open-flavour heavy-light hybrids where one of the hybrid's constituent quarks is a charm or bottom and the other is an up, down, or strange. We compute leading-order, diagonal correlation functions of several hybrid interpolating currents, taking into account QCD condensates up to dimension-six, and extract hybrid mass predictions for all $J<sup>P\in{0<sup>{\pm},\,1<sup>{\pm}}$, as well as explore possible mixing effects with conventional quark-antiquark mesons. Within theoretical uncertainties, our results are consistent with a degeneracy between the heavy-nonstrange and heavy-strange hybrids in all $J<sup>P$ channels. We find a similar mass hierarchy of $1^+$, $1<sup>{-}$, and $0^+$ states (a $1<sup>{+}$ state lighter than essentially degenerate $1<sup>{-}$ and $0<sup>{+}$ states) in both the charm and bottom sectors, and discuss an interpretation for the $0^-$ states. If conventional meson mixing is present the effect is an increase in the hybrid mass prediction, and we estimate an upper bound on this effect.