Resonances in J/ψ→ϕπ+π− and ϕK+K−

Abstract A partial wave analysis is presented of J / ψ → ϕ π + π − and ϕ K + K − from a sample of 58M J / ψ events in the BES II detector. The f 0 ( 980 ) is observed clearly in both sets of data, and parameters of the Flatte formula are determined accurately: M = 965 ± 8 ( stat ) ± 6 ( syst ) MeV / c 2 , g 1 = 165 ± 10 ± 15 MeV / c 2 , g 2 / g 1 = 4.21 ± 0.25 ± 0.21 . The ϕ π π data also exhibit a strong ππ peak centred at M = 1335 MeV / c 2 . It may be fitted with f 2 ( 1270 ) and a dominant 0 + signal made from f 0 ( 1370 ) interfering with a smaller f 0 ( 1500 ) component. There is evidence that the f 0 ( 1370 ) signal is resonant, from interference with f 2 ( 1270 ) . There is also a state in ππ with M = 1790 −30 +40 MeV / c 2 and Γ = 270 −30 +60 MeV / c 2 ; spin 0 is preferred over spin 2. This state, f 0 ( 1790 ) , is distinct from f 0 ( 1710 ) . The ϕ K K ¯ data contain a strong peak due to f 2 ′ ( 1525 ) . A shoulder on its upper side may be fitted by interference between f 0 ( 1500 ) and f 0 ( 1710 ) .