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 $J^P\in \{0^{\pm },1^{\pm }\}$, 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 $J^P$ channels. We find a similar mass hierarchy of $1^{+}$, $1^{-}$, and $0^{+}$ states (a $1^{+}$ state lighter than essentially degenerate $1^{-}$ and $0^{+}$ 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.

24 pages, 8 figures. Mass predictions updated from previous version to reflect corrected sign error in sum rule analysis. Mixing analysis and examination of higher weight sum-rules added. To be published in JHEP