  The implications of the fourth generation quarks in the
B-->K_{1}(1270,1400)l^{+}l^{-} with l=mu, tau decays are studied, where the
mass eigenstates K_{1}(1270) and K_{1}(1400) are the mixture of ^{1}{P}_{1} and
^{3}{P}_{1} states with the mixing angle \theta_{K}. In this context, we have
studied various observables like branching ratio (BR), forward backward
asymmetry (A_{FB}) and longitudinal and transverse helicity fractions (f_{L,T})
of K_{1} meson in B-->K_{1}l^{+}l^{-} decays. To study these observables, we
have used the Light Cone QCD sum rules form factors and set the mixing angle
\theta_{K}=-34^{o}. It is noticed that the BR is suppressed for K_{1}(1400) as
a final state meson compared to that of K_{1}(1270). Same is the case when the
final state leptons are tauons rather than muons. In both the situations all
the above mentioned observables are quite sensitive to the fourth generation
effects. Hence the measurements of these observables at LHC, for the above
mentioned processes can serve as a good tool to investigate the indirect
searches for the existence of fourth generation quarks.
