Measurement of the Differential Branching Fraction and Forward-Backward Asymmetry for B->K(*)l+l-
Abstract
We study B->K(*)l+l- decays based on a large data sample of 657 million BB pairs collected with the Belle detector at the KEKB e+e- collider. The differential branching fraction, the isospin asymmetry, the K* polarization, and the forward-backward asymmetry (AFB) as functions of q2 are reported. The fitted AFB spectrum tends to be shifted toward the positive side from the SM expectation. The measured branching fractions and lepton flavor ratios (electron/muon) are B(B->K*l+l-)=(10.8+1.1-1.0+-0.9)*10-7, B(B->Kl+l-)=(4.8+0.5-0.4+-0.3)*10-7, RK*=1.21+-0.25+-0.08, and RK=0.97+-0.18+-0.06, respectively.
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