Study of $e^{+}{e}^{-}\to \eta \varphi$ via Initial State Radiation at Belle

Abstract

Using $980f{b}^{-1}$ of data collected on and around the ${\rm Y}(nS)(n=1,2,3,4,5)$ resonances with the Belle detector at the KEKB collider, we measure the cross section of $e^{+}{e}^{-}\to \eta \varphi$ from threshold to $3.95\mathrm{GeV}/c^2$ via initial-state radiation. From a multi-parameter fit assuming $\varphi (2170)$ exists in the $\eta \varphi$ final state according to previous measurement by BESIII, the resonant parameters of $\varphi (1680)$ are determined to be $m_{\varphi (1680)}=(1683\pm 7\pm 9)\mathrm{MeV}/c^2$ (statistical and systematic errors, respectively), ${\Gamma }_{\varphi (1680)}=(149\pm 12\pm 13)\mathrm{MeV}$ and, depending on the possible presence of interfering resonances, ${\Gamma }_{\varphi (1680)}^{e^{+}{e}^{-}}\cdot \mathcal{B}[\varphi (1680)\to \eta \varphi ]=(122\pm 6\pm 13)\mathrm{eV}$, $(219\pm 15\pm 18)\mathrm{eV}$, $(163\pm 11\pm 13)\mathrm{eV}$ or $(203\pm 12\pm 18)\mathrm{eV}$. The branching fraction of $\varphi (1680)\to \eta \varphi$ decay is determined to be approximately 20%. Additionally, the branching fraction for $J/\psi \to \eta \varphi$ is measured to be $(7.1\pm 1.0\pm 0.5)\times 10^{-4}$. However, there is no significant observed $\varphi (2170)$ signal in the $\eta \varphi$ final states in this analysis, and correspondingly the upper limit for ${\Gamma }_{\varphi (2170)}^{e^{+}{e}^{-}}\cdot \mathcal{B}(\varphi (2170)\to \eta \varphi )$ is determined to be either $0.17\mathrm{eV}$ (for two fits), or $18.6\mathrm{eV}$ (remaining two fits), at 90% confidence level.

References in corpus (8)

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• X(2175) as a resonant state of the $\varphi K\bar{K}$ system
• New Hadron States
• Analysis of Y(2175) as a tetraquark state with QCD sum rules
• A Candidate for $1^{--}$ Strangeonium Hybrid
• Y(2175): Distinguish Hybrid State from Higher Quarkonium
• The Y(2175) State in the QCD Sum Rule
• Study of the process $e^{+}{e}^{-}\to \varphi \eta$ at center-of-mass energies between 2.00 and 3.08 GeV