Tests of CPT with CPLEAR

Measurements of K/sup 0//K/sup 0/ time dependent asymmetries in pionic and semileptonic decays with the CPLEAR detector enabled a complete determination of CPT violation parameters in the neutral kaon system. A global fit using the Bell-Steinberger relation yielded values for the CPT violation parameter in K/sup 0/ mixing Im( delta ) =(2.4+or-5.0)*10/sup -5/ and Re( delta )=(2.4+or-2.8)*10/sup -4/, the determination of the latter relying essentially on CPLEAR measurements. In addition, CPT violation parameters in semileptonic decays Re(y) and Re(x/sub -/) could be measured for the first time. From these results, the equality of K/sup 0/ and K/sup 0/ masses and lifetimes is tested at the 10/sup -18/ GeV level. Assuming CPT conservation in decays, the 90% C.L. limit on m(K/sup 0/)-m(K/sup 0 /) can be pushed down to 5*10/sup -19/ GeV. CPT violation amplitudes in I=0 and I=2 decays into two pions were excluded at the level of 10 /sup -4/ of the corresponding CPT conserving decay amplitudes. (8 refs).