Precision tests of CPT symmetry and quantum mechanics in the neutral kaon system

We present a systematic phenomenological analysis of the tests of CPT symmetry that are possible within an {\em open} quantum-mechanical description of the neutral kaon system that is motivated by arguments based on quantum gravity and string theory. We develop a perturbative expansion in terms of the three small CPT-violating parameters admitted in this description, and provide expressions for a complete set of K \rightarrow 2\pi, 3\pi and \pi\ell\nu decay observables to second order in these small parameters. We also illustrate the new tests of CPT symmetry and quantum mechanics that are possible in this formalism using a regenerator. Indications are that experimental data from the CPLEAR and previous experiments could be used to establish upper bounds on the CPT-violating parameters that are of order 10^{-19} GeV, approaching the order of magnitude that may be attainable in quantum theories of gravity.