In the Standard Model Extension (SME) for neutral kaons, CPT violation manifests to lowest order only in the mixing parameter delta (e.g. vanish at first order in the decay amplitudes), and exhibits a dependence on the 4-momentum of the kaon.
The analysis of the data of the KLOE experiment already yielded the most precise measurement of the CPT violating parameters in the quark sector of the minimal SME. A re-analysis of the same data in addition with the analysis of the data collected by the KLOE-2 experiment could yield the first measurement of the new violation parameters in the much less restrictive context of the non-minimal SME incorporating the Standard Model of particle physics and General Relativity.
The subject of the project falls into the category of basic research and its cultural and scientific impact is relevant.
As already said the KLOE/KLOE-2 data sample is unique and is expected to remain such for the next years (or decade) to come. Its full exploitation is mandatory as a legacy of the KLOE/KLOE-2 experiment.
At present CPT symmetry seems to be the only exact discrete symmetry in nature. This experimental fact has a solid theoretical basis in the famous CPT theorem, which ensures an exact invariance for CPT symmetry for any quantum field theory formulated on a flat space-time assuming (1) Lorentz invariance, (2) locality, and (3) unitarity (ie conservation of probability). Therefore, testing the validity of CPT invariance (reaching a level of precision close to the interesting Planck scale region), is equivalent to probe with extreme precision the validity of the most fundamental assumptions underlying the present theory of elementary particles and their interactions (Standard Model) or its possible extensions. A possible discovery of any CPT symmetry violation would have a revolutionary impact on our current theoretical framework and would certainly constitute an unambiguous sign of new physics beyond the Standard Model, opening completely new scenarios for the understanding of the currently open problems in fundamental physics and cosmology.
The attempt to reconcile the quantum theory with Einstein's theory of relativity, that is the quantum gravity, constitutes a formidable challenge from a theoretical point of view, as the two theories are apparently highly irreconcilable. The hope of having a solid guide from experiments is thwarted by the extremely small scale (the Planck scale) to which the characteristic effects of quantum gravity are expected to occur. The measurements of some of the parameters of violation of the CPT symmetry in the K meson system constitute a very rare exception with their high precision and offer a unique field of investigation to be fully exploited. The proposed research will widen the boundaries of knowledge, in the hope that the study of these phenomena with different observables and improved precisions could reveal new effects.