Lepton polarization asymmetry in B-->K(*)l+l-

We investigate the longitudinal lepton polarization asymmetry in the exclusive processes B → Kℓ + ℓ − and B → K ∗ ℓ + ℓ − . We include both short and long-distance contributions to the asymmetry in our discussions. We find that average values of the polarization asymmetries of the muon and tau for B → K ( ∗ ) µ + µ − and B → K ( ∗ ) τ + τ − are − 0 . 8 ( − 0 . 7) and − 0 . 2 ( − 0 . 5), respectively.