Investigation of the overlap of excited bottomonium states with hybrid operators

TL;DR

This paper investigates how excited bottomonium states overlap with hybrid operators using NRQCD and the variational method, providing insights into their couplings and state separations.

Contribution

It introduces a detailed analysis of bottomonium state overlaps with hybrid operators employing a variational approach within NRQCD up to order v^4.

Findings

Effective separation of mass eigenstates achieved

Demonstrates the utility of the variational method for excited states

Provides quantitative overlaps for bottomonium excitations

Abstract

We analyze the overlap of color-octet meson operators with the $\Upsilon$ and the $\eta_b$ and their 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.