The KLOE experiment at DAFNE, the Frascati Phi-factory, and its successor KLOE-2, collected the largest existing data sample in the world at an e+e- collider running at the phi-resonance peak energy, corresponding to ~8 fb1 of integrated luminosity, i.e. ~2.4 x 10^10 phi mesons produced.
This unique data sample is very rich in Physics and very prolific in the number of analysis flourishing from it, which is continuously growing.
This partially reflects the truly general purpose concept behind the design of the KLOE/KLOE-2 detector, which is in this respect extremely beneficial.
In this proposal we would like to investigate a peculiar character of neutral kaons, i.e. what is called "strange entanglement", which is specific to two neutral kaon systems in a coherent quantum state with all the interconnections with their properties as single particles: (i) strangeness oscillations (ii) large difference in lifetimes of the physical states (iii) T and CP symmetries violation (iv) extreme sensitivity to CPT violation effects.
A new approach will be adopted in both the theoretical and experimental studies of strange entanglement, not only exploiting this unique quantum phenomenon to perform very fundamental symmetry tests, but also studying and deepening the understanding of the entanglement itself with very different possibilities with respect to other physical systems, as entangled photons, for instance.
The present measurements are far from being exhaustive, and the future analysis and full exploitation of the KLOE/KLOE-2 data will constitute a unique opportunity to deeply explore this field.
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 both for typology and statistical relevance and is very prolific in the number of analysis flourishing from it. At the moment this data sample is expected to remain unique for the next years (or decade) to come and its exploitation is mandatory. In a broad sense it can be considered the legacy of the KLOE/KLOE-2 experiment.
Concerning the strange entanglement and the possibilities it opens to test the fundamental discrete symmetries of Nature, it has to be reminded that 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 in some cases the 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 quantum coherence tests performed using the strange entanglement, i.e. with the entangled neutral K mesons, are the most precise ever made with "massive" systems and involve the non-local aspects of quantum mechanics, among the most bizarre and counterintuitive of the theory, on which the well-known EPR paradox and the formulation of the famous Bell's inequality are founded, verified so far only in entangled photon systems. Therefore a possible observation of decoherence effects would constitute a violation of the laws of quantum mechanics and would have equally revolutionary consequences of the violation of CPT symmetry. 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. As explained above, the measurements of some of the parameters of decoherence and 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.
Here it is worth mentioning that strange entanglement and test of discrete symmetries with transitions could also open up a new possibility to test direct CP violation (epsilon'), trying to shed light on the controversy between experimental results and theory predictions, which might reveal signals of New Physics beyond the Standard Model.
It has also to be noted that the fundamental infrastructure for this research is provided by the only Italian particle collider, the result of years of studies and investments that finds in this project one of its best realization. The proposed frontier research allows KLOE-2 and DAFNE to compete with other major international projects in the effort to discover hints of new physics beyond the Standard Model.
Finally, concerning the applicative and technological potentialities of the proposed research, these are in general indirect and not immediate, as to be expected for all the basic researches that involve the construction of large systems and infrastructures. In this sense, the technological innovation introduced by the realization of the KLOE-2 new detectors and of the DAFNE collider are many, and ranges from the crystal calorimeter technology (CCALT), also used in medical diagnostics applications such as PET, to the innovative Cylindrical GEM technology, adopted in other experiments like BES-III, to the implementation of new techniques for the realization of high-intensity beams, just to name a few.