The phenomenology of the exotic hybrid nonet with $\pi_1(1600)$ and $\eta_1(1855)$

TL;DR

This paper investigates the decay properties of the hybrid nonet with exotic quantum numbers, using a flavor-invariant Lagrangian and experimental data to estimate decay widths and coupling strengths.

Contribution

It provides a detailed analysis of the decay widths and coupling constants of the hybrid nonet, including predictions for the widths of the isoscalar states, linking them to experimental observations.

Findings

The hybrid kaon can be as broad as the $ ext{π}_1(1600)$.

The light isoscalar hybrid is predicted to be narrow.

The heavy isoscalar width matches the observed $ ext{η}_1(1855)$.

Abstract

We study the decays of the $J^{PC}=1^{-+}$ hybrid nonet using a Lagrangian invariant under the flavor symmetry, parity reversal, and charge conjugation. We use the available experimental data, the lattice predictions, and the flavor constraints to evaluate the coupling strengths of the $\pi_1(1600)$ to various two-body mesonic states. Using these coupling constants, we estimate the partial widths of the two-body decays of the hybrid pion, kaon and the isoscalars. We find that the hybrid kaon can be nearly as broad as the $\pi_1(1600)$. Quite remarkably, we find also that the light isoscalar must be significantly narrow while the width of the heavy isoscalar can be matched to the recently observed $\eta_1(1855)$.