Study of J/psi->eta phi pi+pi- at BESIII

Abstract

Based on a sample of $2.25\times 10^{8}J/\ddot{I}ˆ$ events taken with the BESIII detector at the BEPCII collider, we present the results of a study of the decay $J/\ddot{I}ˆ\to \hat{I}\cdot \ddot{I}•\ddot{I}{€}^{+}\ddot{I}{€}^{-}$. The $Y(2175)$ resonance is observed in the invariant mass spectrum of $\ddot{I}•f_0(980)$ with a statistical significance of greater than $10\ddot{I}ƒ$. The corresponding mass and width are determined to be $M=2200\pm 6(stat.)\pm 5(syst.)\mathrm{MeV}/c^2$ and $\hat{I}“=104\pm 15(stat.)\pm 15(syst.)$ MeV, respectively, and the product branching fraction is measured to be $\mathcal{B}(J/\ddot{I}ˆ\to \hat{I}\cdot Y(2175)$, $Y(2175)\to \ddot{I}•f_0(980)$, $f_0(980)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-})=(1.20\pm 0.14(stat.)\pm 0.37(syst.))\times 10^{-4}$. The results are consistent within errors with those of previous experiments. We also measure the branching fraction of $J/\ddot{I}ˆ\to \ddot{I}•f_1(1285)$ with $f_1(1285)\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and set upper limits on the branching fractions for $J/\ddot{I}ˆ\to \ddot{I}•\hat{I}\cdot (1405)$/$\ddot{I}•X(1835)$/$\ddot{I}•X(1870)$ with $\hat{I}\cdot (1405)$/$X(1835)$/$X(1870)\to \hat{I}\cdot \ddot{I}{€}^{+}\ddot{I}{€}^{-}$ at the 90\% confidence level.

11 pages, 11 figures