Search

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]

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. 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. [ABSTRACT FROM AUTHOR]

The development of mathematically complete and consistent models solving the so-called "measurement problem", strongly renewed the interest of the scientific community for the foundations of quantum mechanics, among these the Dynamical Reduction Models posses the unique characteristic to be experimentally testable. In the first part of the paper, an upper limit on the reduction rate parameter of such models will be obtained, based on the analysis of the X-ray spectrum emitted by an isolated slab of germanium and measured by the IGEX experiment. The second part of the paper is devoted to present the results of the VIP (Violation of the Pauli exclusion principle) experiment and to describe its recent upgrade. The VIP experiment established a limit on the probability that the Pauli Exclusion Principle (PEP) is violated by electrons, using the very clean method of searching for PEP forbidden atomic transitions in copper. [ABSTRACT FROM AUTHOR]

The positron annihilation lifetime spectroscopy was applied to the samples of the human uterine leiomyomas and the normal myometrium tissues taken from the selected place of the uterus during a surgery. The method indicated differences in values of the measured positron annihilation lifetime spectroscopy parameters (lifetimes and intensities) between healthy and diseased tissue samples. The additional measurements were performed either in darkness or in presence of visible light which influenced the free radicals present in both kind of tissues and, as a result, made changes in free annihilation and o-Ps decay lifetime and intensity values. [ABSTRACT FROM AUTHOR]

The AMADEUS collaboration has the goal to perform unprecedented measurements in the field of the low-energy charged kaons-nuclei interactions, by implementing the existing KLOE detector with a dedicated setup in the inner region. The KLOE detector at DA ΦNE represents a unique opportunity to perform a complete study of the Λ(1405) resonance through all its three Σπ decay channels. The importance of these measurements relies on the possibility to compare the different results for the various decay channels, investigating their contributions to the final resonance shape. In particular, one of the main differences between the neutral and charged Σπ channels is the presence of a second resonance, the Σ(1385), whose contribution to the final Λ(1405) spectra has to be evaluated and subtracted. Very promising preliminary results have been already obtained for the Σπ decay channel to which, for isospin selection rules, the Σ(1385) resonance can not decay, and for the Σπ decay channel analysis, and will be presented in this work. [ABSTRACT FROM AUTHOR]

We report on preliminary results of the J-PARC E15 experiment aiming to search for the simplest kaonic-nuclear bound-state, K-pp, via in-flight ³He(K-,n) reaction. The first physics data-taking was performed with 5 x 109 incident kaons on the ³He target, and 3 x 105 neutrons were collected by a forward neutron counter placed 15 m away from center of the target at 0 degrees. The semi-inclusive neutron spectrum shows clear peak structure composed of the quasi-elastic K-n → K-n and the charge exchange K- p → ... 0n reactions as expected. [ABSTRACT FROM AUTHOR]

The mass shift of the vector mesons in nuclei is known to be a powerful tool for investigating the mechanism of generating hadron mass from the QCD vacuum. The mechanism is known to be the spontaneous breaking of chiral symmetry. One of the approach to investigate spontaneous breaking of chiral symmetry in nuclear media is formation of meson nucleus bound state and measurring energy level of the state which will be a direct connection to the (...q) expectation value in nucleus. We propose the experiment to study in-medium mass modification of the φ meson using the formation of φ-meson bound state at J-PARC/Japan. We demonstrate that a clear missing-mass spectrum can be obtained efficiently by (..., φ) spectroscopy together with the Λ tagging, using the primary reaction channel ...p → φφ. A systematic study over several nuclear targets will yield a unique, definitive and precise determination of the in-medium mass modification of the vector meson φ(s...). This paper gives an overview of the physics motivation and the detector concept, and explains the direction of the initial research and development effort. [ABSTRACT FROM AUTHOR]

Abstract: The DAΦNE electron–positron collider at the Laboratori Nazionali di Frascati of INFN has made available a unique quality low-energy negative kaons “beam”, which is being used to unlock the secrets of the kaon–nucleon/nuclei interactions at low energies by the SIDDHARTA(-2) and the AMADEUS experiments. SIDDHARTA has already performed unprecedented precision measurements of kaonic atoms, and is being presently upgraded, as SIDDHARTA-2, to approach new frontiers. The AMADEUS experiment already started a data taking with a dedicated carbon target, plans to perform in the coming years precision measurements on kaon–nuclei interactions at low-energies, in particular to study the possible formation of kaonic nuclei and the . The two experiments are briefly presented in this paper. [Copyright &y& Elsevier]

The J-PARC E15 experiment has the aims to search for the simplest kaonic nuclear bound state, K pp, by the in-flight He( K, n) reaction. The exclusive measurement is performed by a simultaneous measurement of the missing mass using the knocked out neutron and the invariant mass via the expected decay, K pp → Λ p → pπ p. In this paper, an overview of the experiment and current data analysis of the engineering runs performed in February and June 2012 are presented. [ABSTRACT FROM AUTHOR]

The mass shift of the vector mesons in nuclei is known to be a powerful tool for investigating the mechanism of generating hadron mass from the QCD vacuum. The mechanism is known to be the spontaneous breaking of chiral symmetry. In 2007, KEK-PS E325 experiment reported about 3.4 % mass reduction of the ϕ meson in medium-heavy nuclei (Cu). This result is possibly one of the indications of the partial restoration of chiral symmetry in nuclei, however, unfortunately it is hard to make strong conclusions from the data. One of the ways to conclude the strength of the ϕ meson mass shift in nuclei will be by trying to produce only slowly moving ϕ mesons where the maximum nuclear matter effect can be probed. The observed mass reduction of the ϕ meson in the nucleus can be translated as the existence of an attractive force between ϕ meson and nucleus. Thus, one of the extreme conditions that can be achieved in the laboratory is indeed the formation of a ϕ-nucleus bound state, where the ϕ meson is 'trapped' in the nucleus. The purpose of the experiment is to search for a ϕ-nucleus bound state and measure the binding energy of the system. We will demonstrate that a completely background-free missing-mass spectrum can be obtained efficiently by $(\bar{p}, \phi)$ spectroscopy together with KΛ tagging, using the primary reaction channel $\bar{p} p \rightarrow \phi \phi$. This paper gives an overview of the physics motivation and the detector concept, and explains the direction of the initial research and development effort. [ABSTRACT FROM AUTHOR]

The data on the reactions K+Xe → K0 γX and K+Xe → K+ γX, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the Θ+(1540) baryon: Θ+ → K0 pγ and Θ+ → K+ nγ. No signals have been observed, and we derive the upper limits Γ(Θ+ → K0 pγ)/Γ(Θ+ → K0 p) < 0.032 and Γ(Θ+ → K+ nγ)/Γ(Θ+ → K+ nγ) < 0.041 which, using our previous measurement of Γ(Θ+ → KN) = 0.39 ± 0.10 MeV, translate to Γ(Θ+ → K0 pγ) < 8 keV and Γ(Θ+ → K+ nγ) < 11 keV at 90% confidence level. We have also measured the cross sections of K+-induced reactions involving emission of a neutral pion: σ( K+ n → K0 pπ0) = 68 ± 18 µb and σ( K+ N → K+ Nπ0) = 30 ± 8 µb for incident K+ momentum of 640 MeV. [ABSTRACT FROM AUTHOR]

The data on the charge-exchange reaction K+Xe → K0 pXe′, obtained with the bubble chamber DIANA, are reanalyzed using increased statistics and updated selections. Our previous evidence for formation of a narrow pK0 resonance with mass near 1538 MeV is confirmed. The statistical significance of the signal reaches some 8 (6) standard deviations when estimated as $$ {S \mathord{\left/ {\vphantom {S {\sqrt B \left( {{S \mathord{\left/ {\vphantom {S {\sqrt {B + S} }}} \right. \kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}}} \right. \kern-\nulldelimiterspace} {\sqrt B \left( {{S \mathord{\left/ {\vphantom {S {\sqrt {B + S} }}} \right. \kern-\nulldelimiterspace} {\sqrt {B + S} }}} \right)}} $$. The mass and intrinsic width of the Θ+ baryon are measured as m = 1538 ± 2 MeV and Γ = 0.39 ± 0.10 MeV. [ABSTRACT FROM AUTHOR]

We have measured the Balmer-series x-rays of kaonic 4He atoms using large-area silicon drift x-ray detectors (SDDs) in order to study the low-energy $\bar{K}$-nucleus strong interaction. The energy of the 3d → 2p transition was determined to be 6467 ± 3(stat) ± 2(syst) eV. The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment. [ABSTRACT FROM AUTHOR]

We have continued our investigation of the charge-exchange reaction K +Xe → K 0 pXe’ in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation of a narrow pK 0 resonance with mass of 1537 ± 2 MeV/ c 2 is observed in the elementary transition K + n → K 0 p on a neutron bound in the xenon nucleus. The visible width of the peak is consistent with being entirely due to instrumental resolution and allows one to place an upper limit on its intrinsic width: Γ < 9 MeV/ c 2. A more precise estimate of the resonance intrinsic width, Γ = 0.36 ± 0.11 MeV/ c 2, is obtained from the ratio between the numbers of resonant and nonresonant charge-exchange events. The signal is observed in a restricted interval of incident K + momentum that is consistent with smearing of a narrow pK 0 resonance by Fermi motion of the target neutron. The statistical significance of the signal is some 7.3, 5.3, and 4.3 standard deviations for the estimators $$S/\sqrt B ,S/\sqrt {S + B} $$ and $$S/\sqrt {S + 2B} $$ , respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of a pentaquark baryon with positive strangeness in the charge-exchange reaction K + n → K 0 p on a bound neutron. [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]

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 J-PARC E15 experiment aims to search for the lightest kaonic nuclear states, namely K-pp, using in-flight (K-, n) reaction on 3He. In this experiment, the missing mass in the (K-, n) reaction and the invariant mass of the decay such as K-pp → Λp → pπ-p will be measured simultaneously. In this article, the experimental feature and the present status are presented. [ABSTRACT FROM AUTHOR]

In this paper we report the reflection efficiency measurements of the VOXES Von Hamos (VH) spectrometer, based on HAPG mosaic crystals, together with ray tracing simulation results. Von Hamos spectrometers are widely used in several fields, ranging from fundamental physics to various practical applications. These types of Bragg spectrometers are usually used in high rate–high resolution experiments, where the typical source size can be as low as a few tens of microns. The VOXES collaboration at the INFN Laboratories of Frascati recently developed a VH spectrometer, making use of HAPG mosaic crystals and optimized X-ray beam optics, which could be used for source sizes up to a few mm in the Bragg plane and some tens of mm in the sagittal plane. Such a spectrometer may open a new era in the field of exotic (kaonic) atom precision measurements, delivering data with unprecedented precision to the nuclear physics community. In order to plan the use of this spectrometer the capabilities in terms of signal collection efficiency need to be checked, reliable ray tracing simulations have to be developed and consistency between data and simulations has to be verified. In this paper, we present this crosscheck for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1,2 and FeKα1,2 XRF lines. For both of them, the experimental results and the simulations are found to be in good agreement within the errors. [ABSTRACT FROM AUTHOR]

J-PET is the first positron-emission tomograph (PET) constructed from plastic scintillators. It was optimized for the detection of photons from electron-positron annihilation. Such photons, having an energy of 511 keV, interact with electrons in plastic scintillators predominantly via the Compton effect. Compton scattering is at most probable at an angle orthogonal to the electric field vector of the interacting photon. Thus registration of multiple photon scatterings with J-PET enables to determine the polarization of the annihilation photons. In this contribution we present estimates on the physical limitation in the accuracy of the polarization determination of 511 keV photons with the J-PET detector. [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]