CPTTests in the Neutral Kaon System

Fermilab experiment E773 has measured the phases ${\Phi }_{+-}{=43.53\mathrm{}}^{\circ }\pm {0.97}^{\circ }$ and ${\Phi }_{00}-{\Phi }_{+-}{=0.62\mathrm{}}^{\circ }\pm {1.03}^{\circ }$ of the $\mathrm{CP}$ violating parameters ${\eta }_{+-}$ and ${\eta }_{00}$ 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 $\mathrm{CPT}$ symmetry and show no evidence for a violation.