CPT and Lorentz Tests in the Standard Model
  A general Lorentz-violating extension of the minimal SU(3) x SU(2) x U(1) standard model is described, including both CPT-even and CPT-odd terms. Some theoretical properties and experimental implications are given. The extension can be regarded as a low-energy limit of a physically relevant Lorentz-covariant fundamental theory in which spontaneous Lorentz violation occurs. 
Alan Kostelecky