Measurement of the transition form factor in

In this work we present a study of the Dalitz decay ϕ → ηe+e−, with η → π0π0π0, performed using 1.7 fb−1 of e+e− collisions collected at KLOE in the 2004-2005 data taking period. The resulting branching fraction is: BR(ϕ → ηe+e−) = (1.075 ± 0.007(stat.) ± 0.038(norm.)) × 10−4. We have also studied the invariant mass of the dilepton system, extracting the slope of the transition form factor: b ϕη =(1.17 ± 0.10 −0.11+0.07) GeV−2. The ϕ → π0e+e− rare decay is also being studied using the same data sample. The branching ratio will be measured, with a consistent reduction of the actual total uncertainty. The double off shell π0 Transition Form Factor will also be measured for the first time in the time-like region, with the momentum transfer given by the e+e− invariant mass