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論文

Quantitative estimation of exposure inhomogeneity in terms of eye lens and extremity monitoring for radiation workers in the nuclear industry

吉富 寛; 古渡 意彦; 萩原 雅之*; 長畔 誠司*; 中村 一*

Radiation Protection Dosimetry, 184(2), p.179 - 188, 2019/08

To manage the equivalent doses for radiation workers, exposure inhomogeneity is an important factor in the decision-making process related to protection measures and additional monitoring. Our previous study proposed the methodology to evaluate the inhomogeneity of exposure quantitatively. In this study, we applied proposed method to five different types of actual exposure situations in the nuclear industry. Two of them were conventionally characterized as homogeneous exposure, but the other three as inhomogeneous exposure. The evaluation of homogeneity exposure was conducted using Monte Carlo calculations with two simplified models, which were then verified with phantom experiments. Consequently, all of the evaluations reproduced the experimental results, implying that our proposed method would be applicable for actual work conditions in the nuclear industry. Furthermore, the two presumed homogeneous exposure situations were found to be rather inhomogeneous because of the contribution of positrons and the limited source region. The investigation also implies that obtaining the information on the most probable posture of the exposed worker, as well as the existence of the weekly penetrating radiation such as $${beta}^{pm}$$ ray as a main source of exposure would be the key for more precise estimation.

論文

Possibility of a new narrow $$Lambda^*$$ resonance near the $$Lambda eta$$ threshold

谷田 聖

AIP Conference Proceedings 2130, p.040019_1 - 040019_6, 2019/07

Evidence for a narrow $$Lambda^*$$ resonance at a mass of about 1665 MeV (just above the combined mass of the $$Lambda$$ ground state plus the $$eta$$ meson) has been seen in the $$M(pK^-)$$ mass of the Dalitz plot for $$Lambda_c to pK^-pi^+$$ decay at the Belle experiment. Additional evidence for this resonance is found in the partial-wave analysis (PWA) of data on $$K^- p$$ reactions done independently by several groups, driven by angular distributions of the $$K^- p to Lambdaeta$$ reaction by the Crystal Ball collaboration. If a narrow $$Lambda^*$$ resonance exists at this mass, then the conventional quark model cannot explain it, and a possible explanation is that it is a crypto-exotic baryon with a dominant meson-baryon component to its wave function. Therefore we have proposed a definitive experiment for $$K^- p to Lambda eta$$, using the newly built hypTPC detector to establish the existence of the proposed narrow $$Lambda(1665)$$ and determine its spin and parity in just two weeks of beamtime at J-PARC (E72). We will discuss these evidences for the proposed $$Lambda^*$$ resonance and introduce the E72 experiment.

論文

Studies of extremely dense matter in heavy-ion collisions at J-PARC

佐甲 博之

Nuclear Physics A, 982, p.959 - 962, 2019/02

 パーセンタイル:100(Physics, Nuclear)

We aim to study extremely dense matter in heavy-ion collisions at 1-19 AGeV/c at a future project of J-PARC (JPARC-HI). We will search for the first order phase boundary and its critical end point in the QCD phase diagram. We also aim at studying the properties of dense matter related to neutron stars and neutron star mergers, in particular the equation of state (EOS). We expect to produce world's highest rate heavy-ion beams of $$10^{11}$$ with the ion species from p to U. We design spectrometers based on a large dipole magnet to measure hadrons, dimuons, and hypernuclei. We evaluate some of key performance of the spectrometers based on detailed simulations.

論文

"$$K^-pp$$", a $$bar K$$-meson nuclear bound state, observed in $$^3$$He($$K^-,Lambda p)n$$ reactions

橋本 直; 谷田 聖; 他67名*

Physics Letters B, 789, p.620 - 625, 2019/02

 パーセンタイル:100(Astronomy & Astrophysics)

$$^{3}{rm He}(K^-, , Lambda p)n$$における$$Lambda p$$不変質量分布において$$m_K + 2m_p$$、つまり$$K^-$$が2つの陽子に束縛する質量閾値以下に顕著なピークを観測した。$$q$$ = 350$$sim$$650MeV/$$c$$という比較的大きな運動量移行領域を選ぶことで、準弾性散乱($$overline{K}N rightarrow overline{K}N$$)に続いて残りの2各紙に吸収される反応($$overline{K}NN rightarrow Lambda N$$)をはっきり分離することができる。観測したピークの単純なフィットによってBreit-Wignerポール位置$$B_{rm {it Kpp}} = 47 pm 3 , (stat.) ,^{+3}_{-6},(sys.)$$ MeV、幅$$Gamma_{rm {it Kpp}} = 115 pm 7 , (stat.),^{+10}_{-20} ,(sys.)$$ MeV、そして$$S$$波ガウス形状因子パラメータ$$Q_{rm {it Kpp}} = 381 pm 14 , (stat.),^{+57}_{-0} ,(sys.)$$MeV/$$c$$という値が"$$K^-pp$$"というストレンジネスを含む新しい原子核束縛システムについて得られた。

論文

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

江川 弘行; 足利 沙希子; 長谷川 勝一; 橋本 直; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 金原 慎二*; 七村 拓野; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02

A double-$$Lambda$$ hypernucleus, $${}_{LambdaLambda}mathrm{Be}$$, was observed by the J-PARC E07 collaborationin nuclear emulsions tagged by the $$(K^{-},K^{+})$$ reaction. This event was interpreted as a production and decay of $$ {}_{LambdaLambda}^{;10}mathrm{Be}$$,$${}_{LambdaLambda}^{;11}mathrm{Be}$$, or $${}_{LambdaLambda}^{;12}mathrm{Be}^{*}$$ via $$Xi^{-}$$ capture in $${}^{16}mathrm{O}$$.By assuming the capture in the atomic 3D state, the binding energy of two $$Lambda$$ hyperons$$,$$($$B_{LambdaLambda}$$)of these double-$$Lambda$$ hypernuclei are obtained to be$$15.05 pm 0.11,mathrm{MeV}$$, $$19.07 pm 0.11,mathrm{MeV}$$, and $$13.68 pm 0.11,mathrm{MeV}$$, respectively. Based on the kinematic fitting, $${}_{LambdaLambda}^{;11}mathrm{Be}$$ is the most likely explanation for the observed event.

論文

First determination of the level structure of an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; et al.

Physical Review Letters, 120, p.132505_1 - 132505_5, 2018/03

 被引用回数:1 パーセンタイル:49.95(Physics, Multidisciplinary)

We report on the first observation of $$gamma$$ rays emitted from an $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F. The energy spacing between the ground state doublet, $$1/2^+$$ and $$3/2^+$$ states, of $$^{19}_{Lambda}$$F is determined to be $$315.5pm0.4({rm stat.})^{+0.6}_{-0.5}({rm syst.})$$ keV by measuring the $$gamma$$-ray energy of the $$M1(3/2^+ to 1/2^+)$$ transition. In addition, three $$gamma$$-ray peaks are observed and assigned as $$E2(5/2^+ to 1/2^+)$$, $$E1(1/2^- to 1/2^+)$$, and $$E1(1/2^- to 3/2^+)$$ transitions. The excitation energies of the $$5/2^+$$ and $$1/2^-$$ states are determined to be $$895.2pm0.3({rm stat.})pm0.5({rm syst.})$$ keV and $$1265.6pm1.2({rm stat.})^{+0.5}_{-0.7}({rm syst.})$$ keV, respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing $$s$$- and $$p$$-shell hypernuclear data.

論文

Studies of the QCD phase diagram with heavy-ion collisions at J-PARC

佐甲 博之

JPS Conference Proceedings (Internet), 20, p.011051_1 - 011051_5, 2018/01

At J-PARC, a future project with heavy-ion collisions to study high baryon density region of the QCD phase diagram is planned. In very high energy heavy-ion collisions at RHIC and LHC, quark-gluon plasma was discovered at high temperature but very low baryon density. On the other hand, little is known about properties of high baryon density matter which can be explored with lower-energy heavy-ion collisions at J-PARC. We will discuss physics to study QCD phase structures and an experimental plan at J-PARC.

論文

Prospect of heavy-ion collision experiments at J-PARC

佐甲 博之

Proceedings of Science (Internet), 311, 10 Pages, 2018/01

In order to explore phase structures in high-baryon density regime of the QCD phase diagram and study dense quark/hadronic matter which may exist in the core of neutron stars, we proposed a heavy-ion program at J-PARC (J-PARC-HI). In heavy-ion collisions at J-PARC (1-19 AGeV/c), the maximum baryon density reaches 5-10 times the normal nuclear density. We designed heavy-ion acceleration scheme at J-PARC. A heavy-ion beam will be produced in a new heavy-ion injector (a linac and a booster ring) and accelerated in the existing 3-GeV and 50-GeV synchrotrons (Rapid-Cycling Synchrotron and Main Ring). We designed a multi-purpose large acceptance Toroidal magnet spectrometer for lepton, photon, and hadron measurements. We also designed a spectrometer which measures hadrons and nuclei only around beam rapidity region to search for various hypernuclei and strangelets. The latter spectrometer could accept the full beam intensity of J-PARC. In this talk, physics goals, experimental design of the spectrometers, and expected physics results will be discussed.

論文

Spectroscopy of nuclei with multi-strangeness by using new S-2S spectrometer at J-PARC

後神 利志*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; et al.

JPS Conference Proceedings (Internet), 18, p.011031_1 - 011031_6, 2017/11

The missing mass spectroscopy of $$Xi^-$$ hypernuclei is planned at the Japan Proton Accelerator Research Complex (J-PARC) by using the $$(K^-,K^+)$$ reaction. We are constructing a new magnetic spectrometer, S-2S, which has a better momentum resolution [$$Delta p/p = 5 times 10^{-4}$$ (FHWM)] than that of an existing spectrometer (SKS) at J-PARC. S-2S would give us an opportunity to confirm the existence of $$Xi^-$$ hypernuclei as a peak structure owing to both the high momentum resolution and its reasonably large solid angle. Brief descriptions of our experiment and of its preparation status are presentedin this article.

論文

Study of baryon excited states in $$(pi,2pi)$$ reactions at J-PARC

佐甲 博之

JPS Conference Proceedings (Internet), 17, p.063004_1 - 063004_2, 2017/07

N*, $$Delta *$$のバリオン励起状態は長年研究されているが、依然として多くの高質量の励起状態が見つかっていない。最近の理論研究で$$pipi N$$が高質量バリオン励起状態の崩壊チャンネルとして大きな寄与を持っていることが分かってきた。このため、$$(pi,2pi)$$生成反応を測定する実験(J-PARC E45)を提案した。本発表ではこの実験の概要と検出器の開発状況について発表する。

論文

$$gamma$$-ray spectroscopy of hypernuclei; Recent results and prospect at J-PARC

田村 裕和*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.011004_1 - 011004_11, 2017/07

The present status and future prospects of precision $$gamma$$-ray spectroscopy of $$Lambda$$ hypernuclei are described. A new experiment (J-PARC E13) has been performed at the J-PARC K1.8 line employing a newly-developed germanium (Ge) detector array, Hyperball-J, via the $$(K^-,pi^-)$$ reaction on $$^4$$He and $$^{19}$$F targets. This is the first study of $$s$$-shell and $$sd$$-shell $$Lambda$$ hypernuclei with Ge detectors. The $$^4$$He target spectrum exhibited a $$gamma$$-ray peak of $$^4_{Lambda}{rm He}(1^+to 0^+)$$ at $$1.406 pm 0.002 pm 0.002$$ MeV. Compared with the energy ($$1.09 pm 0.02$$ MeV) of the corresponding transition for the mirror hypernucleus, $$^4_{Lambda}{rm H}(1^+to 0^+)$$, the present result clearly indicates a large charge symmetry breaking (CSB) effect. This decisive data for CSB allows a stringent test of baryon-baryon interaction models. As for the $$^{19}$$F target run, a preliminary spectrum shows several $$gamma$$-ray peaks assigned to $$^{19}_{Lambda}{rm F}$$ transitions. Future plans of $$gamma$$-ray spectroscopy are also discussed.

論文

Search for excited state of $$Sigma$$ hypernucleus in the J-PARC E13 experiment

中川 真菜美*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012009_1 - 012009_4, 2017/07

One of the main items of the J-PARC E13 experiment is the search for excited states of the $$^4_{Sigma}$$He hypernucleus via the $$^4$$He$$(K^-,pi^-)$$ reaction at 1.5 GeV/c. The missing-mass spectrum of the $$^4$$He$$(K^-,pi^-)X$$ reaction was obtained in an angular range from 0 to 20 degrees. We show the count-base spectrum of the missing-mass in the angular range from 2 to 14 degrees. The ground state of $$^4_{Lambda}$$He and $$^4_{Sigma}$$He were clearly observed in the missing-mass spectrum. We also show three missing-mass spectra divided by the reaction angle.

論文

High statistics $$Sigma p$$ scattering experiment using high intensity pion beams at J-PARC

三輪 浩司*; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 近藤 恭弘; 成木 恵; 佐甲 博之; 佐藤 進; 杉村 仁志; et al.

JPS Conference Proceedings (Internet), 17, p.041002_1 - 041002_6, 2017/07

In order to test theoretical frameworks of the Baryon-Baryon ($$BB$$) interactions and to confirm the "Pauli effect between quarks" for the first time, we have proposed an experiment (J-PARC E40) to measure low-energy hyperon-proton scattering cross sections of the $$Sigma^+ p$$, $$Sigma^- p$$ elastic scatterings and the $$Sigma^- p to Lambda n$$ inelastic scattering in the momentum range of $$400 < p ; ({rm MeV}/c) < 700$$ in the laboratory system. Experimentally, we detect two successive reactions of the $$Sigma$$ production $$(pi^{pm}p to K^+Sigma^{pm})$$ and the $$Sigma p$$ scattering ($$Sigma p to Sigma p$$) in the same liquid hydrogen target. The former is measured with two magnetic spectrometers, and the latter with a scattered proton detector (CATCH). By using a high intensity $$pi$$ beam, we estimate that more than 10000 scattering events can be identified. In this experiment, we aim to provide good quality scattering data to test the theoretical models of the $$BB$$ interaction.

論文

Kaonic-atom X-ray spectroscopy with superconducting microcalorimeters

橋本 直; 谷田 聖; 他45名*

JPS Conference Proceedings (Internet), 17, p.072001_1 - 072001_4, 2017/07

We will measure kaonic helium X-rays using transition-edge-sensor microcalorimeters, TES, in the JPARC hadron experimental facility. To demonstrate the feasibility of the experiment, we performed a measurement of pionic carbon X-rays at PSI, where an excellent FWHM energy resolution of 7 eV at 6.4 keV was achieved. We also evaluated the expected TES performance in the kaon beam at J-PARC. The simulation results show that the TES spectrometer would work with a good energy resolution, and clear peaks of kaonic helium X-rays would be observed on a reasonably suppressed background.

論文

Spectroscopic study of hyperon resonance below $$bar{K}N$$ threshold via the $$d(K^-,n)$$ reaction

井上 謙太郎*; 橋本 直; 谷田 聖; 他69名*

JPS Conference Proceedings (Internet), 17, p.072003_1 - 072003_4, 2017/07

We have taken the data of the $$(K^-,n)$$ reaction on the $$D_2$$ target in May, 2015. In this reaction, it is expected that the $$K^-$$ kicks a neutron and produces the $$Lambda(1405)$$ in a backward angle. We identify the final state of $$K^- d to npi^+pi^-n$$ by detecting the forward neutron, $$pi^+$$ and $$pi^-$$ and obtain the $$d(K^-,n)pi^{mp}Sigma^{pm}$$ spectrum excluded $$K^0$$ and forward-going $$Sigma$$ productions. We observed few hundred events in the region below the $$bar{K}N$$ threshold.

論文

The First gamma-ray spectroscopic study of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F

Yang, S. B.*; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 17, p.012004_1 - 012004_4, 2017/07

The first $$gamma$$-ray spectroscopy of $$sd$$-shell hypernucleus, $$^{19}_{Lambda}$$F, is performed in June, 2015 at the J-PARC K1.8 beam line (J-PARC E13). Precise energy levels of $$^{19}_{Lambda}$$F can be revealed by measured $$gamma$$ rays in this experiment. Especially, the strength of $$Lambda N$$ spin-spin interaction in $$sd$$-shell hypernucleus is obtained through the energy spacing of the ground-state doublet of the hypernucleus. By comparing its strength between the $$s$$, $$p$$, and $$sd$$-shell hypernuclei, a radial dependence $$Lambda N$$ interaction is investigated. The hypernucleus is produced through the $$(K^-,pi^-)$$ reaction with the beam momentum of 1.8 GeV/c. In very preliminary results, we observed two $$gamma$$ rays, and their energies are $$315.8 pm 0.4$$ keV and $$ 895.3 pm 0.3$$ keV where the uncertainties are only statistical.

論文

Missing-mass spectroscopy with the $$^6$$Li$$(pi^-,K^+)X$$ reaction to search for $$^6_Lambda$$H

本多 良太郎*; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 杉村 仁志; et al.

Physical Review C, 96(1), p.014005_1 - 014005_23, 2017/07

AA2017-0465.pdf:1.08MB

 被引用回数:5 パーセンタイル:23.71(Physics, Nuclear)

We searched for the bound state of the neutron-rich $$Lambda$$-hypernucleus $$^6_Lambda$$H, using the $$^6$$Li$$(pi^-,K^+)X$$ double charge-exchange reaction at a $$pi^-$$ beam momentum of 1.2 GeV/$$c$$ at J-PARC. A total of $$1.4 times 10^{12}$$ $$pi^-$$ was driven onto a $$^6$$Li target of 3.5 g/cm$$^2$$ thickness. No event was observed below the bound threshold, i.e., the mass of $$^4_Lambda$$H+$$2n$$, in the missing-mass spectrum of the $$^6$$Li$$(pi^-,K^+)X$$ reaction in the $$2^{circ} < theta_{pi K} <20^{circ}$$ angular range. Furthermore, no event was found up to 2.8 MeV/c$$^2$$ above the bound threshold.

論文

Beamline test of a transition-edge-sensor spectrometer in preparation for kaonic-atom measurements

橋本 直*; 谷田 聖; 他49名*

IEEE Transactions on Applied Superconductivity, 27(4), p.2100905_1 - 2100905_5, 2017/06

We are developing a new technique to apply transition-edge sensors (TESs) to X-ray spectroscopy of exotic atoms, especially of kaonic atoms. To demonstrate the feasibility of this pioneering project, performance of a TES-based X-ray detector was evaluated in pion- and kaon-beam environments at particle accelerators. We successfully observed X-rays from pionic-carbon atoms with a resolution as good as 7 eV FWHM at 6 keV. Also at a kaon beamline, we confirmed that the TES spectrometer will be able to achieve our resolution goal, 6 eV, in our first scientific campaign to measure X-rays from kaonic-helium atoms.

論文

Observation of $$Xi$$ bound states in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$ in J-PARC

永江 知文*; 江川 弘行; 長谷川 勝一; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 谷田 聖; et al.

Proceedings of Science (Internet), 7 Pages, 2017/05

We have carried out a pilot data taking of the J-PARC E05 experiment to search for the bound state peaks of $$^{12}_{Xi}$$Be in the $$^{12}$$C$$(K^-,K^+)X$$ reaction at 1.8 GeV/$$c$$. The measurement was performed at the K1.8 beam line of the J-PARC hadron experimental hall with a typical $$K^-$$ beam intensity of $$6 times 10^5$$ every six seconds. So far the best energy resolution of about 6 MeV FWHM was achieved with the existing SKS spectrometer. With a reasonable statistics, we have succeeded to observe peak structures in the bound region, which seems to suggest that the potential depth of $$Xi$$ would be deeper than 14 MeV estimated in the previous measurements.

論文

Study of the $$overline{K}$$-nucleus interaction by using the $$^{12}$$C(K$$^{-}$$, p) reaction at J-PARC

市川 裕大; 江川 弘行; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; 佐藤 進; et al.

JPS Conference Proceedings (Internet), 13, p.020007_1 - 020007_5, 2017/02

これまで反K中間子と原子核の間の相互作用はK中間子原子(K-中間子と原子核の電磁相互作用による束縛状態)のX線を用いて研究が行われてきた。しかし、このK中間子原子のX線測定では理論モデルの種類によって結果が大きく依存するという問題がため、X線測定だけでは相互作用を決定することが困難である。そこで、われわれは$$^{12}$$C(K$$^{-}$$, p)反応におけるエネルギースペクトルを測定し、理論計算と比較する手法を用いて反K中間子と原子核の間の相互作用を決定しようとしている。この手法は既にKEK E548実験で行われているが、実験セットアップ上の問題点が指摘されているため、過去の高エネルギー加速器研究機構での実験では不十分である。そこで、われわれはJ-PARCにおいて再実験を行い、正しく$$^{12}$$C(K$$^{-}$$, p)のスペクトルを取得することに成功した。

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