Observation of $e^+ e^- \to \eta Y(2175)$ at center-of-mass energies above 3.7$\sim$GeV

TL;DR

This paper reports the first observation of the $Y(2175)$ resonance in the process $e^+ e^- o ext{eta} Y(2175)$ at energies above 3.7 GeV, measuring its properties and cross sections with high significance.

Contribution

It provides the first observation and detailed measurements of the $Y(2175)$ in this specific process, expanding understanding of its production and decay.

Findings

$Y(2175)$ observed with >10σ significance

Mass and width of $Y(2175)$ measured as ($2135 ext{±}8 ext{±}9$) MeV/$c^2$ and ($104 ext{±}24 ext{±}12$) MeV

Production cross section at several hundred femtobarns

Abstract

The state $Y(2175)$ is observed in the process $e^+ e^- \to \eta Y(2175)$ at center-of-mass energies between 3.7 and 4.6$\sim$GeV with a statistical significance larger than $10\sigma$ using data collected with the BESIII detector operating at the BEPCII storage ring. This is the first observation of the $Y(2175)$ in this process. The mass and width of the $Y(2175)$ are determined to be ($2135\pm 8\pm 9$)~MeV/$c^2$ and ($104\pm 24\pm 12$)~MeV, respectively, and the production cross section of $e^+ e^- \to \eta Y(2175)\to \eta\phi f_{0}(980)\to \eta\phi \pi^+ \pi^-$ is at a several hundred femtobarn level. No significant signal for the process $e^+ e^- \to \eta' Y(2175)$ is observed and the upper limit on $\sigma(e^+ e^- \to \eta' Y(2175))/\sigma(e^+ e^- \to \eta Y(2175))$ is estimated to be 0.43 at the 90\% confidence level. We also search for $\psi(3686) \to \eta Y(2175)$. No significant signal is observed, indicating a strong suppression relative to the corresponding $J/\psi$ decay, in violation of the "12\% rule."