Radiative production and decays of the exotic $\eta_1^\prime(1855)$ and its siblings

TL;DR

This paper investigates the radiative production and decay channels of exotic hybrid mesons, especially the $ ext{eta}_1^ ext{'}(1855)$, proposing experimental avenues and analyzing their decay patterns and branching ratios.

Contribution

It introduces a flavor symmetric Lagrangian approach to study hybrid meson production and decay, predicting new decay channels and their sensitivities, and estimates their branching fractions.

Findings

Some decay channels have large branching ratios, comparable to or exceeding known channels.

The $ ext{gamma} ext{eta}f_1(1285)$ channel is promising for detecting the $ ext{eta}_1^{hyb}(1660)$.

Hybrid mesons do not radiatively decay into $I=0$ pseudoscalars, but their vector channels are sensitive to strangeness content.

Abstract

We study the production of the light $J^{PC}=1^{-+}$ hybrid isoscalars $\eta_1^\prime(1855)$ and the yet undiscovered $\eta_1^{hyb}(1660)$ as intermediate states in the radiative decays of the charmonium ($J/\psi$) to two conventional mesons using a flavor symmetric Lagrangian. For this purpose, we use the $J/\psi\to\gamma\eta_1^\prime(1855)\to\gamma\eta\eta^\prime$ process as the reference. We find that some of the decay channels have branching ratios similar to or larger than that of the $\gamma\eta\eta^\prime$ channel and are sensitive to the mixing between the hybrid isoscalars. We propose that relatively stable $\gamma\eta f_1(1285)$ channel be explored for the presence of the light hybrid isoscalar $\eta_1^{hyb}(1660)$. We also exploit the strong decay channels containing at least one vector meson to study the radiative decays of the whole hybrid nonet $\{\pi_1(1600),K_1^{hyb}(1750),\eta_1^{hyb}(1660),\eta_1'(1855)\}$. We find that the hybrids cannot radiatively decay into the $I=0$ pseudoscalars. Furthermore, the vector decay channels ($(\rho/\omega/\phi)\gamma$) of the hybrid isoscalars are sensitive to the strangeness content of the hybrids. We also provide estimates for the branching fractions for the radiative production and partial widths for the radiative decays of the hybrids.