; Lue, Cai-Dian
; Wang, Wei] Inst High Energy Phys, Beijing 100049, Peoples R China
; [Li, Run-Hui] Shandong Univ, Sch Phys, Jinan 250100, Peoples R China
; [Lue, Cai-Dian] Theoret Phys Ctr Sci Facil, Beijing 100049, Peoples R China
Using the B -> K-1 form factors evaluated in the perturbative QCD approach, we study semileptonic B -> K-1(1270)l(+)l(-) and B -> K-1(1400)l(+)l(-) decays, where K-1(1270) and K-1(1400) are mixtures of K-1A and K-1B which are P-3(1) and P-1(1) states, respectively. Using the technique of helicity amplitudes, we express the decay amplitudes in terms of several independent and Lorentz invariant pieces. We study the dilepton invariant mass distributions, branching ratios, polarizations, and forward-backward asymmetries of B -> K(1)l(+)l(-) decays. The ambiguity in the sign of the mixing angle will induce very large differences to branching ratios of semileptonic B decays: branching ratios without resonant contributions either have the order of 10(-6) or 10(-8). But the polarizations and the forward-backward asymmetries are not sensitive to the mixing angles. We find that the resonant contributions will dramatically change the dilepton invariant mass distributions in the resonant region. We also provide the angular distributions of B -> K(1)l(+)l(-)->(K pi pi)l(+)l(-) decays.