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The interaction of antikaons with nucleons and nuclei in the low-energy regime represents an active research field in hadron physics with still many important open questions. The investigation of light kaonic atoms is, in this context, a unique tool to obtain precise information on this interaction. The most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium, were carried out by the SIDDHARTA Collaboration at the DAΦNE electron-positron collider of LNF-INFN, by combining the excellent quality kaon beam delivered by the collider with new experimental techniques, as fast and precise Silicon-Drift X-ray detectors. The measurement of kaonic deuterium will be realized in the near future by SIDDHARTA-2, a major upgrade of SIDDHARTA. [ABSTRACT FROM AUTHOR]

Recent results obtained by the AMADEUS Collaboration on the experimental investigation of the K-low-energy interaction with light nuclei are summarised. The step 0 of AMADEUS consists in the analysis of the data collected at the DAΦNE collider with the KLOE detector during the 2004/2005 data taking campaign. The low momentum K- particles (pK ~ 127 MeV/c) are absorbed in the light nuclei contained in the detector setup (H, 4He, 9Be and 12C) and hyperon-pion/hyperon-nucleons, emitted in the final state, are reconstructed. From the study of Aπ and Ap correlated production, important information on the KN strong interaction in the non-perturbative QCD regime are extracted. [ABSTRACT FROM AUTHOR]

The DAΦNE electron-positron collider of the Laboratori Nazionali di Frascati of INFN has made available a unique quality low-energy negatively charged kaons "beam", which is being used to study the kaon-nucleon/nuclei interactions by the SIDDHARTA-2 experiment and the AMADEUS Collaboration. The dynamics of the strong interaction processes in the non-perturbative regime is approached by lattice calculations and effective field theories (ChPT) which are still lacking experimental results in the low-energy regime, fundamental for their good understanding. The studies of kaonic atoms and of the kaonic nuclear processes performed by SIDDHARTA-2 and AMADEUS play in this context a key-role. [ABSTRACT FROM AUTHOR]

The AMADEUS experiment aims to provide unique quality data for K interaction with nucleons and light nuclei, both at-rest and in-flight (for K momenta of about 100 MeV). The goal is to solve longstanding open issues in the non-perturbative QCD in the strangeness sector, like the nature of the Λ(1405) state, the resonant versus non-resonant yield in nuclear K capture and the properties of kaonic nuclear clusters which are strongly related to the multi-nucleon absorption processes. We can take advantage of the DA ΦNE collider representing a unique source of monochromatic low-momentum kaons, whose nuclear interaction with the materials of the KLOE detector (used as an active target) furnish us excellent acceptance and resolution data for K capture on H, He, Be and 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 C nuclear captures at rest. For the future, new setups for various dedicated targets are under preparation. [ABSTRACT FROM AUTHOR]

SIDDHARTA collaboration performed the highest precision measurement of the shift and width of the kaonic hydrogen 1 s state induced by the strong interaction at the DAΦNE collider of Laboratori Nazionali di Frascati. The result provides vital constraints on the theoretical description of the low-energy $${\bar{K} N}$$ interactions. [ABSTRACT FROM AUTHOR]

With precision X-ray spectroscopy of kaonic hydrogen at the DAΦNE electron-positron collider at Laboratori Nazionali di Frascati the chiral symmetry breaking scenario in the strangeness sector will be investigated by studying the K-p s-wave interaction at threshold. This is possible by observing the strong interaction induced shift and width of the 1s state in kaonic hydrogen atoms. The results of the first measurement at LNF with DEAR (DAΦNE Exotic Atom Research) will be given and the new SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research with Timing Application) project will be described, which is aiming at a substantial improvement of the preceding DEAR result. [ABSTRACT FROM AUTHOR]

The DEAR experiment performed at the DAΦNE electron-positron collider (Frascati, Italy) studied the strong interaction shift and width of the 1 s state in kaonic hydrogen using X-ray spectroscopy. The repulsive character of the kaon-proton interaction at threshold was confirmed and the most precise values of the shift and width were obtained. However, high precision data at the percent level are highly requested to further develop the theories and thus our understanding of the low-energy antikaon-nucleon interaction. Therefore, a new series of precision experiments on kaonic hydrogen and kaonic deuterium are planned at LNF. [ABSTRACT FROM AUTHOR]

The goal of the research program of the Pionic Hydrogen Collaboration at the Paul Scherrer Institute is a precise determination of the shift and width of the pionic hydrogen ground state induced by strong interaction. A crystal spectrometer is used to measure the X-ray transitions to the ground state in order to extract the strong interaction shift and width with a precision of ∼0.2% and ∼1% respectively. The improvement in the precision of the width will amount to almost an order of magnitude compared to the most precise former experiment. The isospin-dependent pion-nucleon scattering lengths can be determined from the shift and width. The high intensity pion beam available at PSI, a cyclotron trap and a high resolution crystal spectrometer provide optimal experimental conditions. For determining the resolution function of the crystal spectrometer the Bragg crystals are characterized using the high intensity X-rays from He-like ions produced in an electron cyclotron resonance ion trap. Measurements of X-ray de-excitation in muonic hydrogen - an exotic atom without strong interaction - were performed to study the effect of Doppler broadening due to Coulomb transition within the electromagnetic cascade which is an important systematic effect in pionic hydrogen and has to be understood in detail. This will allow the determination of the strong interaction width with unsurpassed accuracy, thus resulting in a precise value of the isovector pion-nucleon scattering length. The present status of the experiment and the preliminary results on the strong interaction shift and width are presented. [Copyright &y& Elsevier]

The Pauli Exclusion Principle (PEP) represents one of the fundamental principles of the modern physics and our comprehension of the surrounding matter is based on it. Even if today there are no compelling reasons to doubt its validity, it still spurs a lively debate on its limits, as testified by the abundant contributions found in the literature and in topical conferences. We present a method of searching for possible small violations of PEP for electrons, through the search for "anomalous" X-ray transitions in copper atoms, produced by "fresh" electrons which can decay in a Pauli-forbidden transition to the 1s level, already occupied by two electrons. The VIP Experiment has the scientific goal to improve by four orders of magnitude the present limit on the probability of PEP violation for electrons, bringing it into the 10-30–10-31 region. Preliminary results, together with future plans, are presented. [ABSTRACT FROM AUTHOR]

The Pauli Exclusion Principle is a basic principle of Quantum Mechanics, and its validity has never been seriously challenged. However, given its fundamental standing, it is very important to check it as thoroughly as possible. Here we describe the VIP (VIolation of the Pauli exclusion principle) experiment, an improved version of the Ramberg and Snow experiment (E. Ramberg and G. Snow, Phys. Lett. B238, 438 (1990)); VIP has just completed the installation at the Gran Sasso underground laboratory, and aims to test the Pauli Exclusion Principle for electrons with unprecedented accuracy, down to β2/2 ≈ 10-30 - 10-31. We report preliminary experimental results and briefly discuss some of the implications of a possible violation. [ABSTRACT FROM AUTHOR]

The DEAR (DAΦNE Exotic Atom Research) experiment1 measured the energy of X-rays emitted in the transitions to the ground states of kaonic hydrogen. The shift ∊ and the width Γ of the 1s state are sensitive quantities for tests of the current understanding of the low energy antikaon-nucleon interaction. We obtain ∊1s=-193±37 (stat.)±6 (syst.) and Γ1s=249±112 (stat.)±30 (syst.). [ABSTRACT FROM AUTHOR]

We study kaonic deuterium, the boundK- dstate AK d. Within a quantum field-theoretic and relativistic covariant approach we derive the energy level displacement of the ground state of kaonic deuterium in terms of the amplitude ofK- dscattering for arbitrary relative momenta. Near threshold our formula reduces to the well-known DGBT formula. TheS-wave amplitude ofK- dscattering near threshold is defined by the resonances ?(1405), S(1750) and a smooth elastic background, and the inelastic channelsK- d?NYandK- d?NYp, whereY= S±,S{0} and ?{0}, where the final-state interactions play an important role. The Ericson-Weise formula for theS-wave scattering length ofK- dscattering is derived. The total width of the energy level of the ground state of kaonic deuterium is estimated using the theoretical predictions of the partial widths of the two-body decaysAKd ?NYand experimental data on the rates of theNYpair production in the reactionsK- d?NY. We obtain G{1s} = (630±100)eV. For the shift of the energy level of the ground state of kaonic deuterium we predict e{1s} = (325±60)eV. [ABSTRACT FROM AUTHOR]

We study kaonic hydrogen, the bound K-p state AKp. Within a quantum field theoretic and relativistic covariant approach we derive the energy level displacement of the ground state of kaonic hydrogen in terms of the amplitude of K-p scattering for arbitrary relative momenta. The amplitude of low-energy Kp scattering near threshold is defined by the contributions of three resonances Λ(1405), Λ(1800) and Σ0(1750) and a smooth elastic background. The amplitudes of inelastic channels of low-energy K-p scattering fit experimental data on the near-threshold behaviour of the cross-sections and the experimental data by the DEAR Collaboration. We use the soft-pion technique (leading order in Chiral Perturbation Theory) for the calculation of the partial width of the radiative decay of pionic hydrogen Aπp → n + γ and the Panofsky ratio. The theoretical prediction for the Panofsky ratio agrees well with experimental data. We apply the soft-kaon technique (leading order in Chiral Perturbation Theory) to the calculation of the partial widths of radiative decays of kaonic hydrogen AKp → Λ0 + γ and AKp → Σ0 + γ. We show that the contribution of these decays to the width of the energy level of the ground state of kaonic hydrogen is less than 1%. [ABSTRACT FROM AUTHOR]

The objective of DEAR (DAΦNE Exotic Atom Research) is the measurement of the Kα line shift and width, due to the strong interaction, in kaonic hydrogen and a similar measurement - the first one - in kaonic deuterium. The aim is a precision determination of the antikaon-nucleon isospin dependent scattering lengths in order to obtain the kaon nucleon sigma terms. In a first phase, dedicated to the calibration and optimization of the setup, the experiment collected data on kaonic nitrogen: for the first time a complex of three transitions (7 → 6 at 4.6 keV, 6 → 5 at 7.6 keV and 5 → 4 at 14 keV) was measured, and the corresponding yields obtained. The kaonic hydrogen measurement was performed for a total integrated luminosity of about 60 pb-1 in the last months of the 2002 year. Data analyses are in progress, preliminary results being hereby presented, together with those on kaonic nitrogen. [ABSTRACT FROM AUTHOR]

The DA ΦNE electron-positron collider at the Frascati National Laboratories has made available a unique “beam" of negative kaons providing unprecedented conditions for the study of the low-energy kaon-nucleon interaction, a field still largely unexplored. The DEAR (DA ΦNE Exotic Atom Research) experiment at DA ΦNE and its successor SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) aim at a precision measurement of the strong-interaction shift and width of the fundamental 1 s level, via the measurement of the X-ray transitions to this level, for kaonic hydrogen and kaonic deuterium. The aim is to extract the isospin-dependent antikaon-nucleon scattering lengths and to contribute to the understanding of aspects of chiral symmetry breaking in the strangeness sector. [ABSTRACT FROM AUTHOR]

The determination of low-energy cross sections and branching ratios of the K - multi-nucleon absorption processes in Λ p and Σ 0 p final states performed by the AMADEUS collaboration is presented. Low momentum K - ( p K ≃ 127 MeV / c ) produced at the DA Φ NE collider are impinged on a Carbon target within the KLOE detector and the two and three nucleon absorption processes are disentangled by comparing the experimental data to phenomenological calculations. The Λ p spectra are interpreted in terms of K - multi-nucleon absorption processes; the possible contribution of a K - pp bound state is demonstrated to overlap with the two nucleon capture process, its absolute yield thus resulting indistinguishable. [ABSTRACT FROM AUTHOR]

We report the measurement of K − absorption processes in the Σ 0 p final state and the first exclusive measurement of the two nucleon absorption (2NA) with the KLOE detector. The 2NA process without further interactions is found to be 9% of the sum of all other contributing processes, including absorption on three and more nucleons or 2NA followed by final state interactions with the residual nucleons. We also determine the possible contribution of the ppK − bound state to the Σ 0 p final state. The yield of ppK − / K stop − is found to be ( 0.044 ± 0.009 stat − 0.005 + 0.004 syst ) ⋅ 10 − 2 but its statistical significance based on an F-test is only 1 σ . [ABSTRACT FROM AUTHOR]

Abstract: The PANDA experiment at the planned FAIR facility at GSI, Darmstadt, aims at measuring hadronic final states with unprecedented precision and luminosity. Superior particle identification of charged and neutral particles is mandatory to fulfil PANDA''s physics aims. DIRC (Detection of Internally Reflected Cherenkov light) counters are foreseen for charged particle identification. A barrel DIRC will cover the central region while a disc DIRC will provide particle identification in the forward region. Three DIRC concepts differing in the radiator geometry and method for dispersion correction are studied. The barrel DIRC uses a novel imaging system and aims at exploiting a 3D reconstruction to mitigate dispersion effects. Two concepts are investigated for the forward disc DIRC. One concept employs passive dispersion correction and focussing light guides for image reconstruction. Alternatively, time-of-propagation measurements and a wave-length dependent photon detection system are investigated. The three detector designs share common developments such as investigating radiator properties and photon detection systems, and use the same test beam facilities. [Copyright &y& Elsevier]

Abstract: The powerful particle identification detection system of the (antiProton ANihilations at DArmstadt) experiment contains three Cherenkov detectors. In the forward direction a conventional RICH detector is planned. In the high solenoid field of the target spectrometer thin Cherenkov detectors using the DIRC principle are mandatory and are envisaged in the form of a barrel and a vertical disc. The combination of the time of arrival of the photons with their spatial image determines not only the particle velocity, but also the wavelength of the photons. Therefore dispersion corrections on the lower and upper detection threshold is possible. Investigations concerning the development of a 3D-Barrel-DIRC are discussed as well as two different studies realizing a new Disc-DIRC for the forward angles. One is based on the Time of Propagation (ToP) method the other on the readout with focusing light guides. [Copyright &y& Elsevier]

Abstract: The Pauli exclusion principle (PEP) is one of the basic principles of modern physics and, even if there are no compelling reasons to doubt its validity, it is still debated today because an intuitive, elementary explanation is still missing, and because of its unique stand among the basic symmetries of physics. The present Letter reports a new limit on the probability that PEP is violated by electrons, in a search for an anomalous line in copper: the presence of this line in the soft X-ray copper fluorescence would signal a transition to a ground state already occupied by 2 electrons. The obtained value, , improves the existing limit by almost two orders of magnitude. [Copyright &y& Elsevier]

Abstract: The goal of the DEAR (DAΦNE exotic atom research) experiment is the precise determination of the isospin dependent antikaon–nucleon scattering lengths. The experiment accurately measures the Kα line shift and broadening, due to the strong interaction, in kaonic hydrogen and, for the first time, in kaonic deuterium. A precision measurement of kaonic hydrogen tests chiral symmetry breaking in systems with strangeness. An initial analysis of the DEAR experiment yields a shift and a width , which is more precise than the previous kaonic X-ray experiment KpX at KEK, and allows for the first time to disentangle the full pattern of the kaonic hydrogen K-series line Kα, Kβ and Kγ. [Copyright &y& Elsevier]

The first measurement of the yields of three kaonic nitrogen X-ray transitions, using the DEAR (DAΦNE Exotic Atom Research) setup at the DAΦNE collider of Frascati, is reported. The yields are 41.5±8.7(stat.)±4.1(sys.)% for the n=7→6 transition, 55.0±3.9(stat.)±5.5(sys.)% for the n=6→5 transition and 57.4±15.2(stat.)±5.7(sys.)% for the n=5→4 transition at a density ρ=3.4ρNTP. By using the experimental yields in an atomic cascade calculation, a 1 to 3% K-shell electron population in the n=6 level was deduced. [Copyright &y& Elsevier]