The invariant mass spectra of e+e- pairs produced in 12 GeV proton-induced nuclear reactions are measured at the KEK Proton Synchrotron. On the low-mass side of the meson peak, a significant ...enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.
We report an analysis of the planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the Spitzer Space Telescope. The ground-based ...light curve indicates a low planet–host star mass ratio ofq=(6.9±0.2)×10−5, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. We estimate the host star and planet masses with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability of hosting the planet. The flux variation observed by Spitzer is marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should beΔfSpz<4 instrumental flux units yields a host mass of=-+MM0.37 host 0.210.35 and a planet mass of =-+ÅmM8.4p4.77.9. A Bayesian analysis including the full parallax constraint from Spitzer suggests smaller host star and planet masses of =-+MM0.091 host 0.0180.064 and =-+ÅmM2.1p0.41.5, respectively. Future high-resolution imaging observations with the Hubble Space Telescope or Extremely Large Telescope could distinguish between these two scenarios and help reveal the planetary system properties in more detail.
We developed a radiographic technique to image a subsurface conduit shape using cosmic‐ray muons. The test measurement was performed in Showa‐Shinzan lava dome located in Hokkaido, Japan as an ...example. A muon detector with an area of 6000 cm2 was set up at the foot of the lava dome. Muon tracks recorded in nuclear emulsion films in the detector were analyzed to determine the level of energy absorption along different ray paths through subsurface beneath the lava dome. A typical angular resolution of the muon detector of 10 mrad corresponds to a spatial resolution of 10 m at a distance of 1 km, which is difficult to be addressed with seismological technique. We mapped differentially absorbed cosmic‐ray muons, which depend upon the varying thickness and density beneath the dome. We successfully imaged the conduit shape and determined a conduit diameter of 102 ± 15 m, assuming the observed high absorption region beneath the dome is localized in the vent area.
We have developed a compact detector for measuring beam particles using plastic scintillators readout through Multi-Pixel Photon Counters, which is employed for hypernuclear measurements in the ...WASA-FRS experiment at GSI. The Time-of-Flight resolution of the newly-developed detector has been investigated in relation to the overvoltage with respect to the breakdown voltage, a maximum counting rate of approximately 3×106/s per segment, and a maximum beam charge of Z = 6. The evaluated Time-of-Flight resolutions between the neighboring segments of the detector range from 44.6±1.3 ps to 100.3±3.6 ps (σ) depending on the segment, overvoltage values, and beam intensity. It is also observed that the Time-of-Flight resolution is inversely correlated to the beam atomic charge (Z).
We present an experimental and theoretical investigation of the photon interaction with formic acid in the vacuum-ultraviolet energy range. The absolute absorption cross sections and ionization ...efficiencies were measured in the 11.2–21.4 and 13.5–21.4 eV ranges, respectively, using a double-ion chamber technique. Photoionization and neutral-decay cross sections were derived from these results. From the present ionization cross sections and previously reported ionic dissociative branching ratios, the partial cross sections for dissociating processes were obtained. Theoretically, the photoionization cross sections and the asymmetry parameters of the photoelectron angular distributions for ionization out of the six outermost valence orbitals (10a′, 2a″, 9a′, 1a″, 8a′, and 7a′) were obtained in the energy range from near-threshold to 35 eV. For that, the Padé approximant technique along with the single-center partial-wave expansion method was applied to solve the Lippmann-Schwinger equation in the static-exchange-polarization level of approximation. This is the first theoretical investigation concerning the determination of the asymmetry parameters and photoionization cross sections of formic acid in the vacuum-ultraviolet energy range. Comparison is made between our results and the previous ones.
The WASA-FRS project at GSI and its perspective Saito, T.R.; Achenbach, P.; Alfaki, H. Alibrahim ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
09/2023, Letnik:
542
Journal Article
Recenzirano
Odprti dostop
A novel technique to study bound states of exotic hadrons in subatomic nuclei, such as hypernuclei and mesic nuclei, has been developed by employing the Fragment Separator FRS and the WASA central ...detector at GSI. Two experiments, S447 for studying light hypernuclei, especially hypertriton and a Λnn bound state, and S490 for searching for η’ mesic-nuclei, were recently performed. Data analyses are currently in progress, and light charged particles such as protons and π± are clearly observed and identified in the both experiments. For S447, light nuclear fragments that can also be residual nuclei from decays of hypernuclei of interests have been analysed by the FRS, and a momentum resolution, Δp/p, of 5×10−4 has been achieved. Further data analyses are to be completed. The WASA-FRS project will be continued and extended with the FRS at FAIR Phase 0, and upgrading of the WASA magnet and detectors is currently in progress. Furthermore, construction of a larger detector system with the Super-FRS at FAIR Phase 1 is also under consideration.
Demonstration of a lightguide detector for liquid argon TPCs Bugel, L.; Conrad, J.M.; Ignarra, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2011, Letnik:
640, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We report demonstration of light detection in liquid argon using an acrylic lightguide detector system. This opens the opportunity for development of an inexpensive, large-area light collection ...system for large liquid argon time projection chambers. The guides are constructed of acrylic with TPB embedded in a surface coating with a matching index of refraction. We study the response to early scintillation light produced by a 5.3
MeV
α
. We measure coating responses from 7 to 8 PE on average, compared to an ideal expectation of 10 PE on average. We estimate the attenuation length of light along the lightguide bar to be greater than 0.5
m. The coating response and the attenuation length can be improved. As a benchmark of the present capability, we show a 30 paddle design meets the requirement of the MicroBooNE Experiment, which is efficient triggering on 40
MeV protons produced by neutrino neutral current elastic scatters.
Construction of a new primary beam line, called the B-line, started in 2013 at the J-PARC Hadron Experimental Facility. The B-line is branched at the middle of an existing primary proton beam line ...(A-line) in the beam switching yard (SY), which is the connecting tunnel between the Main Ring (MR) and the Hadron experimental hall (HD-hall). At the branching point, about 0.1% of the primary beam is kicked off at 5 degrees using a Lanbertson magnet and two septum magnets. The Lambertson magnet has a field free hole in its yoke. The proton beam that goes through a field region is separated from the A-line, and it is extracted to the B-line. The rest of the beam that goes through the field free hole is transported through the existing primary beam line. Since a significant beam loss as much as 420 W occurs at the edge of field free hole, the magnets near the Lambertson magnet are operated under a very high radioactive environment. We have developed a "mini-chimney system" regarding easy maintenance of those magnets. The mini-chimney means a vertical tower of approximately 1m in height. The tower is comprised of water pipes, power electrodes, and signal cables for safety interlock. Those can be easily connected and disconnected at the top of chimney on the ceiling iron shields. In this paper we summarize the maintenance scheme developed for the B-line, as well as the design of B-line.In May 2020, the first proton beam was successfully extracted to the B-line by means of the Lambertson and the septum magnets. Up to now, the 10 10 protons per 5.2 sec accelerator cycle shot have been available.
Abstract
Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the ...lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Λnn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.
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