CPT Tests in the Neutral Kaon System

Fermilab experiment E773 has measured the phases Φ_+-0ex0ex=0ex0ex43.53^∘±0.97^∘ and ${{Φ}}₀₀{-}{{Φ}}_{+{-}}{{{0ex}{0ex}}={{0ex}{0ex}}0.62}^{{∘}}±{}{1.03}^{{∘}}$ of the $CP$ violating parameters ${{η}}_{+{-}}$ and ${{η}}₀₀$ from interference in the decay of neutral kaons into two charged or neutral pions from a pair of regenerators. New measurements of the ${K}L$- ${K}S$ mass difference and the ${K}S$ lifetime are also given. These results test $CPT$ symmetry and show no evidence for a violation.