Decay Rate Asymmetry of Top Squark

We discuss a decay rate asymmetry of the top squark, which is induced by a new source of CP violation intrinsic in the supersymmetric standard model. Although new sources of CP violation in this model are severely constrained from the electric dipole moment of the neutron, an unsuppressed CP-violating phase can still coexist with a top squark whose mass is accessible by near-future colliders. Then the dominant decay mode of the top squark has a width different from its CP conjugate process. The magnitude of this $CP$ asymmetry becomes of order $10^{-3}$.