Heavy hybrids in pNRQCD

TL;DR

This paper calculates the masses of heavy quarkonium hybrid states using a QCD-based Born-Oppenheimer approach, combining potential models and lattice QCD, revealing effects of $b5$--doubling and comparing with lattice data and experiments.

Contribution

It introduces a novel calculation of heavy hybrid masses in pNRQCD including $b5$--doubling effects, integrating potential and lattice QCD data.

Findings

Hybrid masses are affected by $b5$--doubling, breaking degeneracies.

Spin multiplets with mixed static energies have lower masses.

Results compare favorably with lattice calculations and experimental candidates.

Abstract

We report on the calculation of the Quarkonium Hybrid masses for the $cg\bar{c}$, $bg\bar{c}$ and $bg\bar{b}$ systems~\cite{hbrpaper}. A QCD analog of the Born-Oppenheimer approximation including the $\Lambda$--doubling terms has been used. The gluonic static energies are obtained combining the short range description from potential non--relativistic QCD (pNRQCD) and lattice QCD calculations. The effect $\Lambda$--doubling terms is to mix the contributions of the static energies to the hybrid states leading to the break of the degeneracy between spin symmetry multiplets with opposite parity. The spin symmetry multiplets with mixed contributions from different static energies have a lower mass with respect to the parity opposite that remains without mixed contributions. We compare with direct lattice calculations and discuss several experimental candidates.