Observation of the exclusive reaction e+e− → ϕη at √-s = 10.58 GeV

Abstract

We report the observation of e + e − → ϕ η near √ s = 10.58 GeV with 6.5 σ significance in the K + K − γ γ final state in a data sample of 224 fb − 1 collected by the BABAR experiment at the PEP-II e + e − storage rings. We measure the restricted radiation-corrected cross section to be σ ( e + e − → ϕ η ) = 2.1 ± 0.4 ( stat ) ± 0.1 ( syst ) fb within the range | cos  θ ∗ | < 0.8 , where θ ∗ is the center-of-mass polar angle of the ϕ meson. The ϕ meson is required to be in the invariant mass range of 1.008 < m ϕ < 1.035 GeV / c 2 . The radiation-corrected cross section in the full cos  θ ∗ range is extrapolated to be 2.9 ± 0.5 ( stat ) ± 0.1 ( syst ) fb .