Improved measurement of the electroweak penguin process B{yields}X{sub s}l{sup +}l{sup -}

We present an improved measurement of the branching fraction for the electroweak penguin process B{yields}X{sub s}l{sup +}l{sup -}, where l is an electron or a muon and X{sub s} is a hadronic system containing an s-quark. The measurement is based on a sample of 152x10{sup 6} {upsilon}(4S){yields}BB events collected with the Belle detector at the KEKB energy asymmetric e{sup +}e{sup -} collider. The X{sub s} hadronic system is reconstructed from one K{sup {+-}} or K{sub S}{sup 0} 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 B(B{yields}X{sub s}l{sup +}l{sup -})=(4.11{+-}0.83(stat){sub -0.81}{sup +0.85}(syst))x10{sup -6} for M{sub l{sup +}}{sub l{sup -}}>0.2 GeV/c{sup 2}.