Mass spectrum of heavy quarkonium hybrids

Abstract

We have extended the calculation of the correlation functions of heavy quarkonium hybrid operators with various J P C quantum numbers to include QCD condensates up to dimension six. In contrast to previous analyses which were unable to optimize the QCD sum-rules for certain J P C , recent work has shown that inclusion of dimension six condensates stabilizes the hybrid sum-rules and permits reliable mass predictions. In this work we have investigated the effects of the dimension six condensates on the remaining channels. After performing the QCD sum-rule analysis, we update the mass spectra of charmonium and bottomonium hybrids with exotic and non-exotic quantum numbers. We identify that the negative-parity states with J P C = (0, 1, 2) −+ , 1 −− form the lightest hybrid supermultiplet while the positive-parity states with J P C = (0, 1) +− , (0, 1, 2) ++ belong to a heavier hybrid supermultiplet, confirming the supermultiplet structure found in other approaches. The hybrid with J P C = 0 −− has a much higher mass which may suggest a different excitation of the gluonic field compared to other channels. In agreement with previous results, we find that the J P C = 1 ++ charmonium hybrid is substantially heavier than the X(3872), which seems to preclude a pure charmonium hybrid interpretation for this state.

Born-Oppenheimer approximation for theXYZmesons

“…The highest-mass state identified in Ref. [49] had the exotic quantum numbers 0 −− . In the Born-Oppenheimer approach, the lowest 0 −− quarkonium hybrid could be a spin-triplet state in the first orbital-angular-momentum excitation of the Σ − g hybrid potential.…”

“…A global analysis of the pattern of XY Z states predicted by QCD sum rules would be more useful. Such an analysis has been carried out for charmonium hybrids and bottomonium hybrids by Chen et al [49]. They identified a total of 10 hybrid states, with the same pattern of masses for charmonium hybrids and bottomonium hybrids.…”

The hidden-charm pentaquark and tetraquark states

“…The mass of the charmonium hybrid meson was also studied in QCD sum rules in Ref. [737,738,739,740,741,742,743,744].…”

Exploring the spectrum of heavy quarkonium hybrids with QCD sum rules

“…[23], the 1 ++ channel was also updated, confirming previous results [18][19][20] for this channel. A comprehensive QSR study of these and all remaining channels was performed in [24], thereby providing updated mass predictions for the spectra of charmonium hybrids and bottomonium hybrids. The remainder of this article will discuss the QSR analysis performed in Ref.…”

“…The remainder of this article will discuss the QSR analysis performed in Ref. [24] and its implications for …”