Probing New Physics in $B\to K^{(\ast )}{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decays

We study the exclusive decays of $B\to K^{(\ast )}{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ by the results in the perturbative QCD with the heavy quark effective theory and lattice calculations. We obtain the form factors for the $B\to K^{(\ast )}$ transitions in the whole allowed region. Our predictions on the branching ratios of $B\to K \ell^{+} \ell^{-}$,$B\to K^{} e^{+}e^{-}$,and$B\to K^{} \mu^{+} \mu^{-}$are$0.53\pm 0.05 ^{+0.10}{-0.07}$,$1.68\pm 0.17^{+0.14}{-0.09}$,and$1.34\pm 0.13 ^{+0.11}_{-0.06}\times 10^{-6}$, where the errors are from the quark mixing elements and hadronic effects, respectively. We also find that our definitions of the T-odd observable and the up-down asymmetry of the $K$ meson in $B\to K^{\ast }{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}\to K\pi {\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ can be used to probe new physics.