Bounds on CPT and Lorentz Violation from Experiments with Kaons

Possible signals for indirect CPT violation arising in experiments with neutral kaons are considered in the context of a general CPTand Lorentz-violating standard-model extension. Certain CPT observables can depend on the meson momentum and exhibit sidereal variations in time. Any leading-order CPT violation would be controlled by four parameters that can be separately constrained in appropriate experiments. Recent experiments bound certain combinations of these parameters at the level of about 10 GeV. Experiments using neutral-meson oscillations can place constraints of remarkable precision on possible violations of CPT invariance. For kaons, recent results [1, 2, 3] bound the CPT figure of merit rK ≡ |mK −mK |/mK to less than a part in 10. Other experiments [4, 5, 6] are expected to improve this bound in the near future. Experiments with neutral-B mesons [7, 8] have also placed high-precision constraints on possible CPT violation, and the B and charm factories should produce additional bounds on the heavy neutral-meson systems. A purely phenomenological treatment of possible CPT violation in the kaon system has been known for some time [9]. In this approach, a complex phenomenological parameter δK allowing for indirect CPT violation is introduced in the standard relationships between the physical meson states and the strong-interaction eigenstates. No information about δK itself can be obtained within this framework. However, over the past ten years a plausible theoretical framework allowing the possibility of CPT violation has been developed. It involves the notion of spontaneous breaking of CPT and Lorentz symmetry in a fundamental theory [10], perhaps arising at the Planck scale from effects in a quantum theory of gravity or string theory, Invited talk at KAON ’99, Chicago, Illinois, June 1999 Physics Department, Indiana University, Bloomington, IN 47405, U.S.A.