Two-photon formation of the η in the reaction e+e- e+e- η e+e- π+ π- γ has been studied for nearly real and virtual photons at an e +e - center-of-mass energy of 29 GeV. The γγ width of the η is found to be 4.5±0.3(stat.)±0.7(syst.) keV. The measured dependence of this yy width upon the photon four-momentum squared in the range 0-5 GeVJ agrees with predictions both from QCD and from ρ dominance. A spin analysis results in a strong preference for a spin-zero, relative to a spin-two, assignment for the η. No evidence for C-parity violation is founc in this η π+ π- γ decay mode.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)