e+e− → K+K−π+π−, K+K−π0π0 and K+K−K+K− cross sections measured with initial-state radiation

Abstract

We study the processes e + e − → K + K − π + π − γ , K + K − π 0 π 0 γ and K + K − K + K − γ , where the photon is radiated from the initial state. About 34 600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232 fb − 1 of BABAR data. The invariant mass of the hadronic final state defines the effective e + e − center-of-mass energy, so that the K + K − π + π − γ data can be compared with direct measurements of the e + e − → K + K − π + π − reaction; no direct measurements exist for the e + e − → K + K − π 0 π 0 or e + e − → K + K − K + K − reactions. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from e + e − → ϕ ( 1020 ) f 0 ( 980 ) and study its structure near threshold. In the charmonium region, we observe the J / ψ in all three final states and several intermediate states, as well as the ψ ( 2 S ) in some modes, and measure the corresponding branching fractions. We see no signal for the Y ( 4260 ) and obtain an upper limit of B Y ( 4260 ) → ϕ π + π − ⋅ Γ Y e e < 0.4 eV at 90% C.L.