Study of the process e+e− → K+K−η with the CMD-3 detector at the VEPP-2000 collider

Abstract The process e + e − → K + K − η has been studied in the center-of-mass energy range from 1.59 to 2.007 GeV using the data sample of 59.5 pb−1, collected with the CMD-3 detector at the VEPP-2000 e + e − collider in 2011, 2012 and 2017. The K + K − η final state is found to be dominated by the contribution of the ϕ ( 1020 ) η intermediate state. The cross section of the process e + e − → ϕ ( 1020 ) η has been measured with a systematic uncertainty of 5.1% on the base of 3009 ± 67 selected events. The obtained cross section has been used to calculate the contribution to the anomalous magnetic moment of the muon: a μ ϕ η ( E 1.8 GeV ) = ( 0.321 ± 0.015 stat ± 0.016 syst ) × 10 − 10 , a μ ϕ η ( E 2.0 GeV ) = ( 0.440 ± 0.015 stat ± 0.022 syst ) × 10 − 10 . From the cross section approximation the ϕ ( 1680 ) meson parameters have been determined with better statistical precision, than in previous studies.