Measurement of the Electroweak Penguin ProcessB→Xsℓ+ℓ−

We report the first measurement of the branching fraction for the inclusive decay B → X s l + l - , where l is either an electron or a muon, and X s is a hadronic recoil system that contains an s quark. We analyzed a data sample of 65.4 x 10 6 B meson pairs collected with the Belle detector at the KEKB e + e - asymmetric-energy collider. We find B(B → X s l + l - ) = [6.1 ′ 1.4(stat) + 1 . 4 - 1 . 1 (syst)] × 10 - 6 for dilepton masses greater than 0.2 GeV/c 2 .