Measurement of the Differential Branching Fraction and Forward-Backward Asymmetry for B ---> K(*)l+l-

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 (A_FB) as functions of q^2 are reported. The fitted A_FB 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, R_K*=1.21+-0.25+-0.08, and R_K=0.97+-0.18+-0.06, respectively.

Note:

8 pages, 5 figures

13.20.He
13.25.Hw
electron positron: annihilation
B: pair production
B: semileptonic decay
isospin: asymmetry
angular distribution: asymmetry
K*(892): polarization
momentum transfer dependence
B: branching ratio

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Figures(7)

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