Neutral kaons produced in the correlated pairs at the DAFNE phi-factory offer unique possibilities to perform fundamental tests of CPT invariance, as well as of the basic principles of quantum mechanics. The analysis of the data collected by the KLOE experiment allows to improve results on several parameters describing CPT violation and decoherence and to measure the regeneration cross section on the beam pipe materials.
Neutral kaon pairs produced in phi decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process phi->K_S K_L->pi+pi-pi+pi- based on 1.7 fb-1 of data collected by the KLOE experiment at the Frascati phi-factory DAFNE. The data are used to perform a measurement of the CPT-violating parameters Delta_amu for neutral kaons in the contest of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are: Delta_ao = (-6.0 +- 7.7_{stat} +- 3.1_{syst}) x 10^{-18} GeV Delta_ax = ( 0.9 +- 1.5_{stat} +- 0.6_{syst}) x 10^{-18} GeV Delta_ay = (-2.0 +- 1.5_{stat} +- 0.5_{syst}) x 10^{-18} GeV Delta_az = ( 3.1 +- 1.7_{stat} +- 0.5_{syst}) x 10^{-18} GeV These are presently the most precise measurements in the quark sector of the Standard Model Extension.
We briefly illustrate a few tests of quantum mechanics which can be performed with entangled neutral kaon pairs at a Phi-factory. This includes a quantitative formulation of Bohrs complementarity principle, the quantum eraser phenomenon and various forms of Bell inequalities.
Neutral kaons produced in correlated pairs at a phi-factory offer unique possibilities to perform fundamental tests of CPT invariance, as well as of the basic principles of quantum mechanics. The analysis of the data collected by the KLOE experiment at DAFNE is still ongoing with the aim of improving previous results and limits on several parameters describing CPT violation and decoherence. Ancillary measurements like the regeneration cross section on the beam pipe materials are also in progress and will be very useful to reduce the systematic uncertainties. Prospects on improvements at the KLOE-2 experiment, aiming at an increase of the integrated luminosity of about a factor of ten with an upgraded detector, will be also discussed.
The KLOE-2 experiment at the INFN Laboratori Nazionali di Frascati (LNF) completed its data-taking at the $e^+ e^-$ DA$Phi$NE collider, which implements an innovative collision scheme based on a crab-waist configuration, and achieved the integrated luminosity of more than 5 fb$^-1$. KLOE-2 represents the continuation of KLOE with an upgraded detector and an extended physics program which includes, among the main topics, neutral kaon interferometry and test of discrete symmetries . Entangled neutral kaon pairs produced at DA$Phi$NE are a unique tool to test discrete symmetries and quantum coherence at the utmost sensitivity, strongly motivating the experimental searches of possible CPT violating effects, which would constitute an unambiguous signal of New Physics. The status of the test of Time reversal and CPT simmetry in $phi to mbox{K}_S mbox{K}_L to pi u,3pi^0,(2pi)$ decays with KLOE and KLOE-2 data will be discussed.
In this paper we present a novel CPT symmetry test in the neutral kaon system based, for the first time, on the direct comparison of the probabilities of a transition and its CPT reverse. The required interchange of in $leftrightarrow$ out states for a given process is obtained exploiting the Einstein-Podolsky-Rosen correlations of neutral kaon pairs produced at a $phi$-factory. The observable quantities have been constructed by selecting the two semileptonic decays for flavour tag, the $pipi$ and $3pi^0$ decays for CP tag and the time orderings of the decay pairs. The interpretation in terms of the standard Weisskopf-Wigner approach to this system, directly connects CPT violation in these observables to the violating $Redelta$ parameter in the mass matrix of $K^0$-$bar{K^0}$, a genuine CPT violating effect independent of $Delta Gamma$ and not requiring the decay as an essential ingredient. Possible spurious effects induced by CP violation in the decay and/or a violation of the $Delta S= Delta Q$ rule have been shown to be well under control. The proposed test is thus fully robust, and might shed light on possible new CPT violating mechanisms, or further improve the precision of the present experimental limits. It could be implemented at the DA$Phi$NE facility in Frascati, where the KLOE-2 experiment might reach a statistical sensitivity of $mathcal{O}(10^{-3})$ on the newly proposed observable quantities.