Couplings of hybrid operators to ground and excited states of bottomonia

TL;DR

This paper investigates how local color-octet meson operators overlap with ground and excited bottomonium states using NRQCD, demonstrating the effectiveness of the variational method in separating states and extracting couplings.

Contribution

It applies the variational method with a basis of operators to analyze couplings of hybrid operators to bottomonium states up to order v^4 in NRQCD, including excited states.

Findings

Variational method effectively separates mass eigenstates.

Clear identification of couplings to excited bottomonium states.

Demonstrates the utility of operator basis in spectral analysis.

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.