Measurements of the observed cross sections for exclusive light hadron production in e+e− annihilation at s=3.773 and 3.650 GeV

By analyzing the data sets of 17.3 pb−1 taken at s=3.773 GeV and 6.5 pb−1 taken at s=3.650 GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in e+e− annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for ψ(3770) decay to these final states at 90% C.L.