The K¯N system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series X-rays of kaonic hydrogen ...atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As X-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ϵ1s=−283±36(stat)±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy K¯N interaction.
Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in ...and out states required for a genuine test involving an antiunitary transformation implied by time-reversal is implemented exploiting the entanglement of K0K‾0 pairs produced at a ϕ-factory.
A data sample collected by the KLOE experiment at DAΦNE corresponding to an integrated luminosity of about 1.7 fb−1 is analysed to study the Δt distributions of the ϕ→KSKL→π+π−π±e∓ν and ϕ→KSKL→π±e∓ν3π0 processes, with Δt the difference of the kaon decay times. A comparison of the measured Δt distributions in the asymptotic region Δt≫τS allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method.
The Multi-Pixel Photon Counter (MPPC) detectors consist of hundreds of micro silicon Avalanche PhotoDiodes (APD) working in Geiger mode. The high gain and the small dimensions typical of these ...devices, together with their good performances in magnetic field, make them ideal readout devices for scintillating fibers as trigger detectors in particle and nuclear physics experiments like AMADEUS, where such a system is planned to be used to trigger on charged kaons. A prototype setup for this trigger system, consisting of 5 scintillating fibers readout by 10 MPPCs, was built and tested in laboratory and mounted inside the DAΦNE collider at LNF-Frascati to measure the back-to-back K+K− pairs emitted in the Φ-decay processes. The ad hoc readout electronics was designed and realized at Laboratori Nazionali di Frascati (INFN). A 64 channels setup, with a new dedicated electronics, was then built and characterized in the laboratory. The results of the tests are presented and discussed.
In the last decades huge theoretical effort was devoted to the development of consistent theoretical models, aiming to solve the so-called "measurement problem". Among these, the Dynamical Reduction ...Models possess the unique characteristic to be experimentally testable, thus enabling to set experimental upper bounds on the reduction rate parameter λ characterizing these models. By analysing the X-ray spectrum emitted by an isolated slab of Germanium, we set the most stringent limit on the λ parameter up to date.
Many experiments investigated the violation of the Pauli Exclusion Principle (PEP) since its discovery in 1925. The VIP (VIolation of the Pauli Principle) experiment tested the PEP by measuring the ...probability for an external electron to be captured and undergo a 2p to 1s transition during its cascading process, where the 1s state is already occupied by two electrons. This transition is forbidden by the Pauli Exclusion Principle. The VIP experiment resulted in a preliminary upper limit for the probability of the violation of the PEP of 4.7×10
−29
. Currently a setup for the follow-up experiment VIP 2 is under preparation. The goal of this experiment is to improve the upper limit for the violation of the PEP by two orders of magnitude, by different improvements like enhanced energy resolution of the X-ray detectors and by implementing an active shielding. Here we report currently ongoing performance tests of the new parts of the setup.
Many experiments investigated the possible violation of the Pauli Exclusion Principle (PEP) since its discovery in 1925. The VIP(Violation of the Pauli Principle) experiment tested the PEP by ...measuring the probability for an external electron to be captured and undergo a 2p to 1s transition during its cascading process, with the 1s state already occupied by two electrons. This transition is forbidden by the PEP. The VIP experiment resulted in an upper limit for the probability of PEP violation of 4.7 × 10−29. Currently a setup for the follow up experiment VIP2 is under preparation. The goal of this experiment is to improve the upper limit for the violation of the PEP by two orders of magnitude, by using new X-ray detectors and by implementing an active shielding. We then present the idea of using an analogous experimental technique to search for X rays as a signature of the spontaneous collapse of the wave function, predicted by the continuous spontaneous localization theories, and discuss some very encouraging preliminary results.
The AMADEUS experiment has the aim to perform studies of the low energy hadronic interactions of negatively charged kaons with nucleons and nuclei, which are fundamental to solve longstanding open ...questions in the non-perturbative QCD in the strangeness sector. The DAphiNE collider provides a unique source of monochromatic low-momentum kaons, whose nuclear interaction with the materials of the KLOE detector (used as an active target) provide us excellent acceptance and resolution data for K super(-) capture on H, super(4)He, super(9)Be and super(12)C, both at-rest and in-flight. AMADEUS step 0 consisted in the analysis of the 2004-2005 KLOE data. A second step consisted in the implementation in the central region of the KLOE detector of a pure graphite target, providing a high statistic sample of K super(-) super(12)C nuclear captures at rest. For the future, new setups for various dedicated targets are under preparation. The aim of such investigations is to face the major open questions in hadron nuclear physics in the strangeness sector, such as the nature of the E(1405) state and the resonant versus non-resonant yield in nuclear K super(-) capture, the possible existence of kaonic nuclear clusters, strongly related to a quantitative understanding of single versus multi-nucleon K super(-) absorption.
Low-energy QCD is still lacking experimental results, fundamental for reaching a good understanding of the strangeness sector. The information provided by the low energy kaon- nucleon/nuclei ...interaction is accessible through the study of kaonic atoms and kaonic nuclear processes. The lightest atomic systems, namely the kaonic hydrogen and the kaonic deuterium, provide the isospin dependent kaon-nucleon scattering lengths by measuring the X-rays emitted during their de-excitation to the 1s level. The most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium and of upper-level transitions in kaonic helium 3 and kaonic helium 4 were carried out at the DAΦNE collider by the SIDDHARTA collaboration. Presently, a significantly upgraded setup developped by the SIDDHARTA-2 collaboration is ready to perform a precise measurement of kaonic deuterium and, afterwards, of heavier exotic atoms. In parallel, the kaon-nuclei interaction at momenta below 130 MeV/c is studied by the AMADEUS collaboration, using the KLOE detector and a dedicated setup inserted in the central region, near the interaction point. Preliminary results of the study of charged antikaons interacting with nuclei are shown, including an analysis of the controversial Λ(1405).
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