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 \(J^{P} \in\left{0^{\pm},1^{\pm}\right}\), 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.