  Top squark (stop) plays a crucial role in the naturalness of supersymmetry
(SUSY) models, which has been extensively searched for in the LHC experiments.
Due to the parity-violating couplings, top quark and chargino thus produced
from stop decay are expected to be polarized. We investigate the polarization
of top quark and chargino, from which we find that the mass differences between
neutralino and stop/chargino can affect the degree of polarization of top
quark/chargino in the stop decay. We then examine the top polarization effects
on kinematics of stop decay in natural SUSY (NSUSY) at the LHC and the results
show that several observables have the discriminating power for different
polarized top quark at the LHC, which may be useful for testing the nature of
stop couplings in NSUSY.
