Improved Measurement of the Electroweak Penguin Process B->Xsll

Abstract

We present an improved measurement of the branching fraction for the electroweak penguin process B->Xsll, where l is an electron or a muon and Xs is a hadronic system containing an s-quark. The measurement is based on a sample of 152*10^6 Upsilon(4S) -> BB events collected with the Belle detector at the KEKB energy asymmetric e+e- collider. The Xs hadronic system is reconstructed from one K^{+-} or K^{0}_{S} and up to four pions, where at most one pion can be neutral. Averaging over both lepton flavors, the inclusive branching fraction is measured to be Br(B->Xsll)=(4.11+-0.83(stat)+0.85-0.81(syst))*10^{-6} for M_ll > 0.2GeV/c2.