[show abstract][hide abstract] ABSTRACT: The study of the [Formula: see text] system at very low energies plays a key role for the understanding of the strong interaction between hadrons in the strangeness sector. At the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati we studied kaonic atoms with [Formula: see text] and [Formula: see text], taking advantage of the low-energy charged kaons from Φ-mesons decaying nearly at rest. The SIDDHARTA experiment used X-ray spectroscopy of the kaonic atoms to determine the transition yields and the strong interaction induced shift and width of the lowest experimentally accessible level (1s for H and D and 2p for He). Shift and width are connected to the real and imaginary part of the scattering length. To disentangle the isospin dependent scattering lengths of the antikaon-nucleon interaction, measurements of [Formula: see text] and of [Formula: see text] are needed. We report here on an exploratory deuterium measurement, from which a limit for the yield of the K-series transitions was derived: [Formula: see text] and [Formula: see text] (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium experiment is introduced.
Nuclear Physics A 06/2013; 907(100):69-77. · 1.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: The nuclear physics program of the ASACUSA experiment at the Antiproton Decelerator (AD) at CERN is concerned with the measurements of antiproton-nuclei cross-sections at low energies (from 5.3 MeV down to the 100 keV region). These measurements are expected to contribute to understand the dynamics of the annihilation process. We give here a full description of the experimental apparatus used for the measurements at 5.3 MeV.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2013; 711:12–20. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: The study of the KbarN system at very low energies plays a key role for the
understanding of the strong interaction between hadrons in the strangeness
sector. At the DAFNE electron-positron collider of Laboratori Nazionali di
Frascati we studied kaonic atoms with Z=1 and Z=2, taking advantage of the
low-energy charged kaons from Phi-mesons decaying nearly at rest. The SIDDHARTA
experiment used X-ray spectroscopy of the kaonic atoms to determine the
transition yields and the strong interaction induced shift and width of the
lowest experimentally accessible level (1s for H and D and 2p for He). Shift
and width are connected to the real and imaginary part of the scattering
length. To disentangle the isospin dependent scattering lengths of the
antikaon-nucleon interaction, measurements of Kp and of Kd are needed. We
report here on an exploratory deuterium measurement, from which a limit for the
yield of the K-series transitions was derived: Y(K_tot)<0.0143 and
Y(K_alpha)<0.0039 (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium
experiment is introduced.
[show abstract][hide abstract] ABSTRACT: We have performed an inclusive spectroscopy of 122Sn(d,
3He) reaction near the pion emission threshold at an incident
energy of Td = 250 MeV/nucleon. The first experiment aims as
devloping the high precision spectroscopy of pionic atoms at the RI beam
factory (RIBF) of RIKEN, which leads to a new project, pionic Atom
Factory project (piAF) to measure pionic atoms for a wide range of
elements. We report the analysis status of the pilot experiment.
[show abstract][hide abstract] ABSTRACT: We are going to perform an inclusive spectroscopy experiment of η′ mesic nuclei with the 12C(p,d) reaction to study in-medium properties of the η′ meson. In nuclear medium, the η′ meson mass may be reduced due to partial restoration of chiral symmetry. In case of sufficiently large mass reduction and small absorption width of η′ at normal nuclear density, peak structures of η′ mesic states in 11C will be observed near the η′ emission threshold even in an inclusive spectrum. The experiment will be carried out at GSI with proton beam supplied by SIS using FRS as a spectrometer. The detail of the experiment is described.
Few-Body Systems 10/2012; 54(7-10). · 1.05 Impact Factor
[show abstract][hide abstract] ABSTRACT: The eta' meson mass may be reduced due to partial restoration of chiral
symmetry. If this is the case, an eta'-nucleus system may form a nuclear bound
state. We plan to carry out a missing-mass spectroscopy with the 12C(p,d)
reaction at GSI-SIS. Peak structures corresponding to such a bound state may be
observed even in an inclusive measurement, if the decay width is narrow enough.
[show abstract][hide abstract] ABSTRACT: A new spectrometer system was designed and constructed at the secondary beam
line K1.8BR in the hadron hall of J-PARC to investigate $\bar K N$ interactions
and $\bar K$-nuclear bound systems. The spectrometer consists of a high
precision beam line spectrometer, a liquid $^3$He/$^4$He/D$_2$ target system, a
Cylindrical Detector System that surrounds the target to detect the decay
particles from the target region, and a neutron time-of-flight counter array
located $\sim$15 m downstream from the target position. Details of the design,
construction, and performance of the detector components are described.
[show abstract][hide abstract] ABSTRACT: A liquid helium-3 target system was developed for experimental studies of
kaonic atoms and kaonic nuclei at J-PARC. helium-3 gas is liquefied in a heat
exchanger cooled below 3.2 K by decompression of liquid helium-4. To maintain a
large acceptance of the cylindrical detector system for decay particles of
kaonic nuclei, efficient heat transport between the separate target cell and
the main unit is realized using circulation of liquid helium-3. To minimize the
amount of material, a vacuum vessel containing a carbon fiber reinforced
plastic cylinder having an inside diameter of 150 mm and a thickness of 1 mm
was produced. A target cell made of pure beryllium and beryllium-aluminum alloy
was developed not only to minimize the amount of material but to obtain also
high x-ray transmission. During a cooling test, the target cell was kept at 1.3
K at a pressure of 33 mbar. The total estimated heat load to the components
including the target cell and heat exchanger cooled by liquid helium-4
decompression, was 0.21 W, and the liquid helium-4 consumption rate was 50
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2012; 687. · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Correlated Λp pairs with smaller invariant mass than the K- + 2p
threshold were observed by recent experiments with stopped K- absorption
in 4He and heavier nuclei, which may be related to the existence of
deeply-bound K-pp states. We discuss a possibility to investigate the
existence of K-pp states by an exclusive measurement with more simple
[show abstract][hide abstract] ABSTRACT: The present paper reviews theoretical and experimental studies of a new type of nuclear spectroscopy for the structure of deeply bound π−π− states and their formation processes through “pion-transfer” nuclear reactions. The calculated energy levels of deeply bound pionic states in heavy nuclei using the standard pion–nucleus optical potential are found to be narrow discrete states even for the 1s1s state in 208Pb. These hitherto unexpected results are caused by the repulsive pion–nucleus optical potential which pushes pionic wavefunctions outwards so that the nuclear absorption of the bound pions is weakened. Theoretical studies on pion-transfer reactions were carried out as a methodological guide to produce these deeply bound pionic states experimentally. In particular, various predictions were made on the pion-transfer proton-pickup reactions (n,d)(n,d) and (dd, 3He). Following these theoretical studies successful experiments on high-resolution spectroscopy of (dd, 3He) reactions were carried out at GSI. The experimental procedures and results together with their theoretical implications are also reviewed. The most important feature of deeply bound 1s1s states of π−π− in heavy nuclei is that it provides unique information on the ss-wave isovector π−Nπ−N interaction which is connected to reduction of chiral symmetry breaking in the nuclear medium. Recent experiments on Pb and Sn isotopes have yielded clear evidence for partial restoration of chiral symmetry in the nuclear medium.
[show abstract][hide abstract] ABSTRACT: A novel method is proposed to measure eta'(958) meson bound states in 11C
nuclei by missing mass spectroscopy of the 12C(p,d) reaction near the eta'
production threshold. It is shown that peak structures will be observed
experimentally in an inclusive measurement in case that the in-medium eta' mass
reduction is sufficiently large and that the decay width of eta' mesic states
is narrow enough. Such a measurement will be feasible with the intense proton
beam supplied by the SIS synchrotron at GSI combined with the good energy
resolution of the fragment separator FRS.
Progress of Theoretical Physics 03/2012; · 2.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: We describe an experiment performed in the ATHENA apparatus in which there is evidence that the antiproton-proton bound state, protonium, has been produced at very low energies in vacuum following the interaction of cold antiprotons with a trapped cloud of molecular hydrogen ions. The latter were confined in a centrifugally separated belt outside a positron plasma used for antihydrogen formation. Studies have been performed at low positron plasma temperatures in which the protonium annihilation signal has been identified along with that from antihydrogen, and we discuss how their contributions can be disentangled. With the positron plasma heated to around 10000 K the ions become distributed in the positrons, and the majority of the annihilation signal can be explained in terms of protonium formation, as antihydrogen creation is heavily suppressed. In this case we compare the observed protonium formation rate with expectations from theory and find reasonable accord, when experimental systematics are taken into account. The effect on the annihilation signals of the passage of an electron current through a pre-loaded positron plasma has been studied in detail, and the results are presented here for the first time.
European Physical Journal Plus 01/2012; 127(124). · 1.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: The largest concern on the cesium-137 ((137)Cs) deposition and its soil contamination due to the emission from the Fukushima Daiichi Nuclear Power Plant (NPP) showed up after a massive quake on March 11, 2011. Cesium-137 ((137)Cs) with a half-life of 30.1 y causes the largest concerns because of its deleterious effect on agriculture and stock farming, and, thus, human life for decades. Removal of (137)Cs contaminated soils or land use limitations in areas where removal is not possible is, therefore, an urgent issue. A challenge lies in the fact that estimates of (137)Cs emissions from the Fukushima NPP are extremely uncertain, therefore, the distribution of (137)Cs in the environment is poorly constrained. Here, we estimate total (137)Cs deposition by integrating daily observations of (137)Cs deposition in each prefecture in Japan with relative deposition distribution patterns from a Lagrangian particle dispersion model, FLEXPART. We show that (137)Cs strongly contaminated the soils in large areas of eastern and northeastern Japan, whereas western Japan was sheltered by mountain ranges. The soils around Fukushima NPP and neighboring prefectures have been extensively contaminated with depositions of more than 100,000 and 10,000 MBq km(-2), respectively. Total (137)Cs depositions over two domains: (i) the Japan Islands and the surrounding ocean (130-150 °E and 30-46 °N) and, (ii) the Japan Islands, were estimated to be more than 5.6 and 1.0 PBq, respectively. We hope our (137)Cs deposition maps will help to coordinate decontamination efforts and plan regulatory measures in Japan.
Proceedings of the National Academy of Sciences 11/2011; 108(49):19530-4. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: We will measure the X‐rays from kaonic 3He3d → 2p transition with a precision below 2 eV. It can provide crucial information on the kaon‐nucleus strong interaction. The experiment (J‐PARC E17) will be performed as Day‐1, which is one of the first experiments in the J‐PARC hadron facility in the year 2011. An overview and the present status of the J‐PARC E17 experiment are described.
[show abstract][hide abstract] ABSTRACT: The KN system at rest makes a sensitive testing ground for low energy QCD. At the DAΦNE electron‐positron collider of Laboratori Nazionali di Frascati we study kaonic atoms, taking advantage of the low‐energy kaons from Φ‐mesons decaying nearly at rest. The DEAR (DAΦNE Exotic Atom Research) experiment at LNF delivered the most precise data on kaonic hydrogen up to now. DEAR and its follow‐up experiment SIDDHARTA (Silicon Drift Detector for Hadronic Atom Research by Timing Application) are using X‐ray spectroscopy of kaonic atoms to measure the strong interaction induced shift and width of the ground state. SIDDHARTA is the first experiment on kaonic helium‐3 and deuterium ever, and kaonic hydrogen was remeasured with improved precision.
[show abstract][hide abstract] ABSTRACT: We are preparing Silicon Drift Detecters (SDDs) for a precision spectroscopy of kaonic helium-3 3d→2p x-rays (~6.2 keV) at J-PARC (E17, DAY-1). Since we need to operate SDDs and their preamplifiers in a cryogenic system, their low-temperature behavior was investigated. The optimal operational temperatures were found to be 110 - 130 K and over 270 K for SDDs and preamplifiers, respectively. In such condition, energy resolution is around 150 eV (FWHM) with 5.9 keV x-rays and time resolution is around 400 ns (FWHM). We also investigated the effect of different incident angles to verify our calibration method in E17. Although response function depends on incident angle, Mn Ka peak positions differ at most 0.5 eV equivalent. Further basic studies of SDDs are ongoing toward the physics run planned in 2011.
Journal of Physics Conference Series 09/2011; 312(5):052009.
[show abstract][hide abstract] ABSTRACT: Physical laws are believed to be invariant under the combined transformations of charge, parity and time reversal (CPT symmetry). This implies that an antimatter particle has exactly the same mass and absolute value of charge as its particle counterpart. Metastable antiprotonic helium (pHe(+)) is a three-body atom consisting of a normal helium nucleus, an electron in its ground state and an antiproton (p) occupying a Rydberg state with high principal and angular momentum quantum numbers, respectively n and l, such that n ≈ l + 1 ≈ 38. These atoms are amenable to precision laser spectroscopy, the results of which can in principle be used to determine the antiproton-to-electron mass ratio and to constrain the equality between the antiproton and proton charges and masses. Here we report two-photon spectroscopy of antiprotonic helium, in which p(3)He(+) and p(4)He(+) isotopes are irradiated by two counter-propagating laser beams. This excites nonlinear, two-photon transitions of the antiproton of the type (n, l) → (n - 2, l - 2) at deep-ultraviolet wavelengths (λ = 139.8, 193.0 and 197.0 nm), which partly cancel the Doppler broadening of the laser resonance caused by the thermal motion of the atoms. The resulting narrow spectral lines allowed us to measure three transition frequencies with fractional precisions of 2.3-5 parts in 10(9). By comparing the results with three-body quantum electrodynamics calculations, we derived an antiproton-to-electron mass ratio of 1,836.1526736(23), where the parenthetical error represents one standard deviation. This agrees with the proton-to-electron value known to a similar precision.
[show abstract][hide abstract] ABSTRACT: We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p¯3He+. Due to the helium nuclear spin, p¯3He+ has a more complex hyperfine structure than p¯4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton.
Physics Letters B 05/2011; 700(1):1-6. · 4.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: ALPHA is an experiment at CERN, whose ultimate goal is to perform a precise test of CPT symmetry with trapped antihydrogen atoms. After reviewing the motivations, we discuss our recent progress toward the initial goal of stable trapping of antihydrogen, with some emphasis on particle detection techniques.
[show abstract][hide abstract] ABSTRACT: In this work we describe the latest results for the measurements of the
hyperfine structure of antiprotonic helium-3. Two out of four measurable
super-super-hyperfine SSHF transition lines of the (n,L)=(36,34) state of
antiprotonic helium-3 were observed. The measured frequencies of the individual
transitions are 11.12548(08) GHz and 11.15793(13) GHz, with an increased
precision of about 43% and 25% respectively compared to our first measurements
with antiprotonic helium-3 [S. Friedreich et al., Phys. Lett. B 700 (2011)
1--6]. They are less than 0.5 MHz higher with respect to the most recent
theoretical values, still within their estimated errors. Although the
experimental uncertainty for the difference of 0.03245(15) GHz between these
frequencies is large as compared to that of theory, its measured value also
agrees with theoretical calculations. The rates for collisions between
antiprotonic helium and helium atoms have been assessed through comparison with
simulations, resulting in an elastic collision rate of gamma_e = 3.41 +- 0.62
MHz and an inelastic collision rate of gamma_i = 0.51 +- 0.07 MHz.
Journal of Physics B Atomic Molecular and Optical Physics 03/2011; · 2.03 Impact Factor