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

الأصل · EN

We study B->K(*)l+l- decays (l=e,mu) based on a data sample of 657 million BB pairs collected with the Belle detector at the KEKB e+e- collider. We report the differential branching fraction, isospin asymmetry, K* polarization, and the forward-backward asymmetry (AFB) as functions of q² = Mll²*c². The fitted AFB spectrum exceeds the Standard Model expectation by 2.7 standard deviations. The measured branching fractions are B(B->K*l+l-)=(10.7+1.1-1.0+-0.9)*10-7 and B(B->Kl+l-)=(4.8+0.5-0.4+-0.3)*10-7, where the first errors are statistical and the second are systematic, with the muon to electron ratios Rₖ*=0.83+-0.17+-0.05 and Rₖ=1.03+-0.19+-0.06, respectively.