Automation of etch pit analyses on solid-state nuclear track detectors with machine learning for laser-driven ion acceleration.

Solid-state nuclear track detectors (SSNTDs) are often used as ion detectors in laser-driven ion acceleration experiments and are considered to be the most reliable ion diagnostics since they are sensitive only to ions and measure ions one by one. However, ion pit analyses require tremendous time and effort in chemical etching, microscope scanning, and ion pit identification by eyes. From a laser-driven ion acceleration experiment, there are typically millions of microscopic images, and it is practically impossible to analyze all of them by hand. This research aims to improve the efficiency and automation of SSNTD analyses for laser-driven ion acceleration. We use two sets of data obtained from calibration experiments with a conventional accelerator where ions with known nuclides and energies are generated and from actual laser experiments using SSNTDs. After chemical etching and scanning the SSNTDs with an optical microscope, we use machine learning to distinguish the ion etch pits from noises. From the results of the calibration experiment, we confirm highly accurate etch-pit detection with machine learning. We are also able to detect etch pits with machine learning from the laser-driven ion acceleration experiment, which is much noisier than calibration experiments. By using machine learning, we successfully identify ion etch pits ∼105 from more than 10 000 microscopic images with a precision of ≳95%. A million microscopic images can be examined with a recent entry-level computer within a day with high precision. Machine learning tremendously reduces the time consumption on ion etch pit analyses detected on SSNTDs.

Mass-resolved ion measurement by particle counting analysis for characterizing relativistic ion beams driven by lasers.

Particle counting analysis is a possible way to characterize GeV-scale, multi-species ions produced in laser-driven experiments. We present a multi-layered scintillation detector to differentiate multi-species ions of different masses and energies. The proposed detector concept offers potential advantages over conventional diagnostics in terms of (1) high sensitivity to GeV ions, (2) realtime analysis, and (3) the ability to differentiate ions with the same charge-to-mass ratio. A novel choice of multiple scintillators with different ion stopping powers results in a significant difference in energy deposition between the scintillators, allowing accurate particle identification in the GeV range. Here, we report a successful demonstration of particle identification for heavy ions, performed at the Heavy Ion Medical Accelerator in Chiba. In the experiment, the proposed detector setup showed the ability to differentiate particles with similar atomic numbers, such as C6+ and O8+ ions, and provided an excellent energy resolution of 0.41%-1.2% (including relativistic effect, 0.51%--1.6%).

A multi-stage scintillation counter for GeV-scale multi-species ion spectroscopy in laser-driven particle acceleration experiments.

Particle counting analysis (PCA) with a multi-stage scintillation detector shows a new perspective on angularly resolved spectral characterization of GeV-scale, multi-species ion beams produced by high-power lasers. The diagnosis provides a mass-dependent ion energy spectrum based on time-of-flight and pulse-height analysis of single particle events detected through repetitive experiments. With a novel arrangement of multiple scintillators with different ions stopping powers, PCA offers potential advantages over commonly used diagnostic instruments (CR-39, radiochromic films, Thomson parabola, etc.) in terms of coverage solid angle, detection efficiency for GeV-ions, and real-time analysis during the experiment. The basic detector unit was tested using 230-MeV proton beam from a synchrotron facility, where we demonstrated its potential ability to discriminate major ion species accelerated in laser-plasma experiments (i.e., protons, deuterons, carbon, and oxygen ions) with excellent energy and mass resolution. The proposed diagnostic concept would be essential for a better understanding of laser-driven particle acceleration, which paves the way toward all-optical compact accelerators for a range of applications.

Monitoring the build-up of hydrogen polarization for polarized hydrogen-deuteride (HD) targets with nuclear magnetic resonance (NMR) at 17 T.

We report on the frozen-spin polarized hydrogen-deuteride (HD) targets for photoproduction experiments at SPring-8/LEPS. Pure HD gas with a small amount of ortho-H2 (∼0.1%) and a very small amount of para-D2 (∼0.001%) was liquefied and solidified by liquid helium. The temperature of the produced solid HD was reduced to about 30 mK with a dilution refrigerator. A magnetic field (17 T) was applied to the HD to grow the polarization with the static method. After the aging of the HD at low temperatures in the presence of a high-magnetic field strength for three months, the polarization froze. Almost all ortho-H2 molecules were converted to para-H2 molecules. Most remaining para-D2 molecules were converted to ortho-D2 molecules. The para-H2 and ortho-D2 molecules exhibited weak spin interactions with the HD. If the concentrations of the ortho-H2 and para-D2 were reduced appropriately at the beginning of the aging process, the aging time can be shortened. We have developed a new nuclear magnetic resonance (NMR) system to measure the relaxation times (T1) of the 1H and 2H nuclei with two frequency sweeps at the respective frequencies of 726 MHz and 111 MHz and succeeded in the monitoring of the polarization build-up at decreasing temperatures from 600 mK to 30 mK at 17 T. Automatic NMR measurements with the frequency sweeps enabled us to omit the use of a manual tuning circuit and to remove magnetic field sweeps with eddy current heat. This technique enables us to optimize the concentration of the ortho-H2 and to efficiently polarize the HD target within a shortened aging time.

Differential Cross Section and Photon-Beam Asymmetry for the γ[over →]p → π

Differential cross sections and photon-beam asymmetries for the γ[over →]p→π^{-}Δ^{++}(1232) reaction have been measured for 0.7

Interference Effect between ϕ and Λ(1520) Production Channels in the γp→K

The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrt[s]=2.1 GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

Spin-density matrix elements for γp→K*0Σ+ at Eγ=1.85-3.0 GeV with evidence for the κ(800) meson exchange.

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.

Near-threshold Lambda(1520) production by the gamma(p)-->K{+}Lambda(1520) reaction at forward K+ angles.

Differential cross sections and photon-beam asymmetries for the gamma(p)-->K{+}Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6or=5/2 or by a new reaction process, for example, an interference effect with the phi photoproduction having a similar bump structure in the cross sections.

Near-threshold photoproduction of Lambda(1520) from protons and deuterons.

Photoproduction of Lambda(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K+/0 angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K+ angles.

Cross sections and beam asymmetry for K;{+}Sigma;{*-} photoproduction from the deuteron at E_{gamma}=1.5-2.4 GeV.

The Sigma(1385) resonance, or Sigma;{*}, is well known as part of the standard baryon decuplet with spin J=3/2. Measurements of the reaction gammap-->K;{+}Sigma;{*0} are difficult to extract due to overlap with the nearby Lambda(1405) resonance. However, the reaction gamman-->K;{+}Sigma;{*-} has no overlap with the Lambda(1405) due to its charge. Here we report the first measurement of cross sections and beam asymmetries for photoproduction of the Sigma;{*-} from a deuteron target. The cross sections at forward angles range from 0.4 to 1.2 mub, with a broad maximum near E_{gamma} approximately 1.8 GeV. The beam asymmetries are negative, in contrast with positive values for the gamman-->K;{+}Sigma;{-} reaction.

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV.

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Near-threshold diffractive psi-meson photoproduction from the proton.

Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV.

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Dipole excitation of alpha clusters in (6)Li and (7)Li.

Dipole excitations in highly excited energy regions of (6)He and (7)He nuclei were investigated via the ((7)Li,(7)Be) reaction with an incident energy of 65A MeV at forward scattering angles. The resonances at Q approximately equal to -30 MeV observed commonly for both (6)Li and (7)Li targets were found to be excited via both spin-flip and spin-nonflip transitions with DeltaL = 1. Based on the observed excitation energy, width, and cross section of each resonance, the relevant resonances are inferred to be analogs of the dipole resonances of alpha clusters in the (6)Li and (7)Li nuclei.

Production of (4)(double Lambda)H hypernuclei.

An experiment demonstrating the production of double-Lambda hypernuclei in (K(-),K(+)) reactions on (9)Be was carried out at the D6 line in the BNL alternating-gradient synchrotron. The technique was the observation of pions produced in sequential mesonic weak decay, each pion associated with one unit of strangeness change. The results indicate the production of a significant number of the double hypernucleus (4)(double Lambda)H and the twin hypernuclei (4)(Lambda)H and (3)(Lambda)H. The relevant decay chains are discussed and a simple model of the production mechanism is presented. An implication of this experiment is that the existence of an S = -2 dibaryon more than a few MeV below the double Lambda mass is unlikely.

Observation of spin-orbit splitting in lambda single-particle states.

The spin-orbit splitting of Lambda single-particle states in (13)(Lambda)C was measured. The 13C(K-,pi(-))(13)(Lambda)C reaction was used to excite both the 1/2(-) and 3/2(-) states simultaneously, which have predominantly 12C(0(+)) x p(Lambda) configuration. gamma rays from the states to the ground state were measured in coincidence with the pi(-)'s, by which ls splitting was found to be 152+/-54(stat)+/-36(syst) keV. The value is 20-30 times smaller than exhibited by the ls splitting in the nuclear shell model. This value gives us new insight into the YN interaction.

Soft dipole resonance in the neutron-skin nucleus 6He

A candidate for a soft dipole resonance, a dipole oscillation mode between a core cluster and a neutron skin, was observed at Ex = 4+/-1 MeV and with a width of 4+/-1 MeV in 6He via the 6Li( 7Li, 7Be) reaction at an incident energy of 65A MeV and forward scattering angles including 0 degrees. Its cross section is deduced to be sigma(0 degrees ) = 0.9+/-0.2 mb/sr. This value is comparable to that of the giant dipole resonance simultaneously measured.

Water extract of defatted rice bran suppresses visceral fat accumulation in rats.

Rice bran has been reported to inhibit pancreatic lipase activity in vitro. This action shows that administration of rice bran may result in a decrease in plasma triglyceride levels and suppress accumulation of fat in vivo. We administered water extract of defatted rice bran (WED-rice bran) to rats to determine its effects. Single administration of WED-rice bran at a dose of 1 g/kg body weight caused a decrease in plasma triglyceride levels in fat emulsion induced hypertriglyceridemic rats. Four week administration of WED-rice bran suppressed accumulation of visceral fat and body weight gain without influencing food consumption, liver function, and renal function. These results indicate that a reduction of plasma triglycerides and suppression of visceral fat accumulation may be induced by pancreatic lipase inhibition caused by administration of WED-rice bran.

Amitriptyline-induced constipation in cynomolgus monkeys is beneficial for the evaluation of laxative efficacy.

In an attempt to create an animal model of constipation in monkeys, amitriptyline was administered to cynomolgus monkeys at doses of 10-160 mg/kg body weight via a nasogastric tube. Normal control monkeys excreted feces frequently throughout the day. Monkeys treated with amitriptyline at doses of 10-40 mg/kg showed delays in feces excretion. The 60 mg/kg treated monkeys for the most part did not excrete feces during the 24 h after amitriptyline administration. The 80 and 120 mg/kg treated monkeys did not excrete feces until 24 h from administration of amitriptyline, and also showed prolonged crouching and lethargy. On the other hand, 160 mg/kg treated monkeys died within 24 h after administration. We therefore felt that the optimal dose for creating constipation in the monkeys was 60 mg/kg. We tested the appropriateness of this amitriptyline-induced constipated monkey model by observing the effects of a new laxative, the herbal medicine ND-10 and the commercially available laxative bisacodyl. Control monkeys (those not receiving ND-10 or bisacodyl) treated with 60 mg/kg amitriptyline did not excrete feces up to 32 h after amitriptyline administration in 2 of 3 monkeys. However, all monkeys treated with one tablet of ND-10 excreted feces. Also, in 4 monkeys administrated with bisacodyl, 3 excreted feces. In this study, we confirmed that constipation can be caused in cynomolgus monkeys by oral administration of amitriptyline. This model may also be useful for the evaluation of laxatives.