Study of the Reactions e⁺e^-→π⁺π^-<i>π</i>^π<i>π</i>^π<i>π</i>^π<i>π</i>^π and <i>π</i>⁺<i>π</i>^-<i>π</i>^π<i>π</i>^π<i>π</i>^πη at Center-of-Mass Energies from Threshold to 4.5 GeV Using Initial-State Radiation

Abstract

We study the processes e+e−→ π+π−π0π0π0π0γ and π+π−π0π0π0ηγ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 7300 and 870 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb−1. The invariant mass of the hadronic final state defines the effective e+e− center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the e+e− → π+π−π0π0π0π0 and the e+e− → π+π−π0π0π0η cross sections are performed. The contributions from ωπ0π0π0, ηπ+π−π0, ωη, and other intermediate states are presented. We observe the J=ψ and ψ(2S) in most of these final states and measure the corresponding branching fractions, many of them for the first time.