Couplings of hybrid operators to ground and excited states of bottomonia

Abstract

We analyze the overlap of local color-octet meson operators with the $\Upsilon$ and the $\eta_b$ and their low-lying excited states, especially the first radial excitations. Our analysis is based on NRQCD and includes all terms up to order $v^4$. We use a variety of source and sink operators as a basis for the variational method, which enables us to clearly separate the mass eigenstates and hence to extract the desired amplitudes. The results show the usefulness of the variational method for determining couplings to excited hadronic states.