Observation of Y(2175) in $J/\psi\to \eta\phi f_0(980)$

TL;DR

This paper reports the observation of the Y(2175) resonance in $J/\psi$ decays, measuring its mass, width, and production rate, confirming its existence and properties consistent with previous observations by BABAR.

Contribution

First observation of Y(2175) in $J/\psi$ decays with detailed measurements of its mass, width, and production branching ratio, supporting its identification as a $1^{--}$ state.

Findings

Y(2175) observed at 2.186 GeV/$c^2$ with 5$\sigma$ significance.

Measured width of Y(2175) is approximately 0.065 GeV/$c^2$.

Branching ratio for $J/\psi o\eta Y(2175)$ with $Y(2175) o\phi f_0(980)$ is about $3.23 imes 10^{-4}$.

Abstract

The decays of $J/\psi\to \eta\phi f_0(980) (\eta\to \gamma\gamma, \phi \to K^+K^-, f_0(980)\to\pi^+\pi^-)$ are analyzed using a sample of $5.8 \times 10^{7}$ $J/\psi$ events collected with the BESII detector at the Beijing Electron-Positron Collider (BEPC). A structure at around $2.18 $GeV/$c^2$ with about $5\sigma$ significance is observed in the $\phi f_0(980)$ invariant mass spectrum. A fit with a Breit-Wigner function gives the peak mass and width of $m=2.186\pm 0.010 (stat)\pm 0.006 (syst) $GeV/$c^2$ and $\Gamma=0.065\pm 0.023 (stat)\pm 0.017 (syst) $GeV/$c^2$, respectively, that are consistent with those of Y(2175), observed by the BABAR collaboration in the initial-state radiation (ISR) process $e^+e^-\to\gamma_{ISR}\phi f_0(980)$. The production branching ratio is determined to be $Br(J/\psi\to\eta Y(2175))\cdot Br(Y(2175)\to\phi f_0(980))\cdot Br(f_0(980)\to\pi^+\pi^-)=(3.23\pm 0.75 (stat)\pm0.73 (syst))\times 10^{-4}$, assuming that the Y(2175) is a $1^{--}$ state.