Heavy Hybrids from NRQCD

TL;DR

This paper reports a lattice QCD calculation of heavy hybrid bottomonium states, revealing a nearly degenerate band of states around 1.6 GeV above the ground state, with implications for experimental detection.

Contribution

It provides the first quenched lattice NRQCD calculation of the lowest lying $b ar b g$-hybrid states, demonstrating their energy levels and potential experimental signatures.

Findings

Existence of a nearly degenerate hybrid state band at ~1.6 GeV above ground state

Hybrid states lie near the $B ar B_J^*$-threshold, above the $B ar B$-threshold

Results align with phenomenological models and static limit lattice calculations

Abstract

We present a quenched lattice calculation for the lowest lying $b \bar b g$-hybrid states in the framework of NRQCD using the leading order Hamiltonian up to ${\cal O}(mv^2)$. We demonstrate the existence of a nearly degenerate rotational band of states with an excitation energy approximately 1.6 GeV above the $\Upsilon$ ground state. This lies around the $B \bar B_J^*$-threshold but well above the $B \bar B$-threshold. Therefore a heavy hybrid signal may well be detected if the centre-of-mass energy in B-factories is raised a few hundred MeV to coincide with other resonances above the 4S state. Our prediction is consistent with most phenomenological models and lattice calculations carried out in the static limit.