The dynamics of the strong interaction processes in the non-perturbative regime is currently approached by lattice calculations and effective field theories (ChPT), still lacking several experimental ...results, fundamental for a good understanding of the strangeness sector. Among these, the information provided by the low-energy kaon nucleon/nuclei interaction, accessible through the study of kaonic atoms and kaonic nuclear processes, plays a key-role. The lightest atomic systems, the kaonic hydrogen and the kaonic deuterium, deliver, in a model-independent way, the isospin-dependent kaon-nucleon scattering lengths, through the X- ray spectroscopy of the exotic atoms de-exciting to the fundamental level. The most precise kaonic hydrogen measurement to-date, together with an exploratory measurement of kaonic deuterium, were carried out in 2009 at the DAΦNE collider, by the SIDDHARTA collaboration. Nowadays, an upgraded setup was built, for a precise measurement of kaonic deuterium and, eventually, of heavier exotic atoms. A correlated study of the kaon-nuclei interaction at momenta below 130 MeV/c is carried out by the AMADEUS collaboration, using the KLOE detector and dedicated targets inserted near the collider interaction point. Preliminary results of the study of charged antikaons interacting with nuclei are shown, including a discussion of the still controversial Λ(1405).
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.
We present the idea of searching for X-rays as a signature of the mechanism inducing the spontaneous collapse of the wave function. Such a signal is predicted by the continuous spontaneous ...localization theories, which are solving the “measurement problem” by modifying the Schrödinger equation. We will show some encouraging preliminary results and discuss future plans and strategy.
Large-area silicon drift detectors (SDDs) were used for the first time in the background condition of a collider for precision spectroscopy of the kaonic atom X-rays in the SIDDHARTA experiment for ...the study of the strong interaction in a low-energy regime. The measurements were performed at the
DA
Φ
NE
electron–positron collider (LNF, Italy), using gas targets of hydrogen, deuterium, helium-3, and helium-4. A test measurement using the kaonic
4He X-rays showed an excellent performance of the SDD devices under the beam conditions, and a good background suppression capability using the time correlation between the kaonic atom X-rays and the back-to-back correlated K
+K
− pairs produced by
φ
decays.
The strong interaction of antikaons (K−) with nucleons and nuclei in the low-energy regime represents an active research field connected intrinsically with few-body physics. There are important open ...questions like the question of antikaon nuclear bound states - the prototype system being K−pp. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DAΦNE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound K−p atom leading to a hadronic shift ϵ1s and a hadronic broadening Γ1s of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering lengths have been calculated constrained by the SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent scattering lengths a measurement of the hadronic shift and width of kaonic deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic deuterium are in preparation (SIDDHARTA2). Many improvements in the experimental setup will allow to measure kaonic deuterium which is challenging due to the anticipated low X-ray yield. Especially important are the data on the X-ray yields of kaonic deuterium extracted from a exploratory experiment within SIDDHARTA.
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 exotic atoms where one atomic 1s electron is replaced by a K−, the strong interaction between the K− and the nucleus introduces an energy shift and broadening of the low-lying kaonic atomic ...levels which are determined by only the electromagnetic interaction. By performing X-ray spectroscopy for Z = 1,2 kaonic atoms, the SIDDHARTA experiment determined with high precision the shift and width for the 1s state of K− p and the 2p state of kaonic helium-3 and kaonic helium-4. These results provided unique information of the kaon-nucleus interaction in the low energy limit.
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