  A combined analysis of the electromagnetic pion and kaon form factors in the
neighborhood of J/psi and psi(2S) and of the strong decay amplitude of these
resonances into kaons is presented. In the presence of a large relative phase
between strong and electromagnetic resonance amplitudes the branching ratio, as
measured in electron-positron annihilation, receives an additional contribution
from the interference between resonance and continuum amplitude neglected in
earlier papers. Our study is model independent and does not rely on the SU(3)
symmetry assumptions used in earlier papers. We note that the large relative
phase between strong and electromagnetic amplitudes observed in earlier
analyses is model dependent and relies critically on the specific assumptions
on SU(3) symmetry and breaking.
