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論文

Search for the 6$$alpha$$ condensed state in $$^{24}$$Mg using the $$^{12}$$C+$$^{12}$$C scattering

Fujikawa, Y.*; Kawabata, T.*; Adachi, S.*; 廣瀬 健太郎; 牧井 宏之; 西尾 勝久; Orlandi, R.; 洲嵜 ふみ; 他13名*

Physics Letters B, 848, p.133834_1 - 133834_6, 2024/01

We searched for the 6$$alpha$$-condensed state in $$^{24}$$Mg by measuring the $$^{12}$$C+$$^{12}$$C scattering with the SAKRA Si detector array. By using the invariant-mass method for the detected 3$$alpha$$ particles, the inclusive cross sections for the $$^{12}$$C+$$^{12}$$C $$rightarrow$$ $$^{12}$$C(0$$^{+}_{2}$$) + X and $$^{12}$$C(3$$^{-}_{1}$$) + X reactions were determined. In both the inclusive $$^{12}$$C(0$$^{+}_{2}$$) + X channel and the exclusive $$^{12}$$C(0$$^{+}_{2}$$) + $$^{12}$$C(0$$^{+}_{1}$$) channel, the cross section peaked at E$$_{cm}$$ = 19.4 MeV, which correspond to the excitation energy of E$$_{x}$$ = 33.3 MeV in $$^{24}$$Mg. This 19.4-MeV state is a candidate for the 6$$alpha$$-condensed state

論文

Evolution of nuclear structure in the neutron-rich $$^{96,97,99}$$Nb isotopes; Evidence for shape coexistence in $$N$$=58 $$^{99}$$Nb

Kumar, V.*; Chapman, R.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; 他13名*

Physical Review C, 108(4), p.044313_1 - 044313_19, 2023/10

The nuclear structure of neutron-rich niobium isotopes $$^{96,97,98}$$Nb were studied at the Legnaro National Laboratories using $$gamma$$-ray spectroscopy. The isotopes were produced in two different experiments, either using multi-nucleon transfer reactions of $$^{96}$$Zr 530-MeV beam onto a $$^{124}$$Sn target, or via fusion-fission of $$^{36}$$S on $$^{176}$$Yb. The level schemes of these isotopes were extended respectively up to excitation energies of 4545, 5409, and 3814 keV. The structure of the low-lying states in these isotopes was interpreted and discussed in the context of shell-model calculations. In particular, for the $$^{99}$$Nb isotope ($$Z$$=41, $$N$$=58), the results indicate the presence of shape-coexistence at low-energies, which was observed for the first time in this isotope.

論文

Update of inclusive cross sections of single and pairs of identified light charged hadrons

Seidl, R.*; 谷田 聖; Belle Collaboration*; 他136名*

Physical Review D, 101(9), p.092004_1 - 092004_13, 2020/05

 被引用回数:5 パーセンタイル:37.47(Astronomy & Astrophysics)

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a 558 fb$$^{-1}$$ data sample collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Azimuthal asymmetries of back-to-back $$pi^pm-(pi^0,eta,pi^pm)$$ pairs in $$e^+e^-$$ annihilation

Li, H.*; 谷田 聖; Belle Collaboration*; 他131名*

Physical Review D, 100(9), p.092008_1 - 092008_26, 2019/11

 被引用回数:8 パーセンタイル:49.32(Astronomy & Astrophysics)

This work reports the first observation of azimuthal asymmetries around the thrust axis in $$e^+e^-$$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $$pi^0$$ and $$eta$$ mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The $$pi^0$$ and $$eta$$ asymmetries rise with the relative momentum $$z$$ of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $$H_1^{perp}$$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the $$eta$$ final states will provide additional information on the flavor structure of $$H_1^{perp}$$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb$$^{-1}$$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.

論文

Gamma-ray spectrum from thermal neutron capture on gadolinium-157

萩原 開人*; 矢野 孝臣*; Das, P. K.*; Lorenz, S.*; 王 岩*; 作田 誠*; 木村 敦; 中村 詔司; 岩本 信之; 原田 秀郎; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.023D01_1 - 023D01_26, 2019/02

 被引用回数:29 パーセンタイル:87.26(Physics, Multidisciplinary)

We have measured the $$gamma$$-ray energy spectrum from the thermal neutron capture, $$^{157}Gd(n,gamma)^{158}Gd$$, on an enriched $$^{157}$$Gd target ($$Gd_2O_3$$) in the energy range from 0.11 MeV up to about 8 MeV. The target was placed inside the germanium spectrometer of the ANNRI detector at J-PARC and exposed to a neutron beam from the Japan Spallation Neutron Source (JSNS). Radioactive sources ($$^{60}$$Co, $$^{137}$$Cs, and $$^{152}$$Eu) and the reaction $$^{35}Cl(n,gamma)$$ were used to determine the spectrometer's detection efficiency for $$gamma$$ rays at energies from 0.3 to 8.5 MeV. Using a Geant4-based Monte Carlo simulation of the detector and based on our data, we have developed a model to describe the $$gamma$$-ray spectrum from the thermal $$^{157}Gd(n,gamma)^{158}Gd$$ reaction. While we include the strength information of 15 prominent peaks above 5 MeV and associated peaks below 1.6 MeV from our data directly into the model, we rely on the theoretical inputs of nuclear level density and the photon strength function of $$^{158}$$Gd to describe the continuum $$gamma$$-ray spectrum from the $$^{157}Gd(n,gamma)^{158}Gd$$ reaction. The results of the comparison between the observed $$gamma$$-ray spectra from the reaction and the model are reported in detail.

論文

Re-acceleration of ultra cold muon in J-PARC Muon Facility

近藤 恭弘; 長谷川 和男; 森下 卓俊; 大谷 将士*; 二ツ川 健太*; 河村 成肇*; 三部 勉*; 山崎 高幸*; 吉田 光宏*; 北村 遼*; et al.

Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.5041 - 5046, 2018/06

J-PARCにおいて、ミューオニウムをレーザー電離して生成される超低速ミューオン(30meV)を再加速するシステムを開発中である。このようにして得られるミューオンビームは、ミューオンg-2実験で要求される低エミッタンスを満たす。J-PARC E34実験では、g-2を0.1ppmの精度で測定することを目指す。超低速ミューオンは、高周波四重極リニアック(RFQ)、交差櫛形Hモードドリフトチューブリニアック、ディスクアンドワッシャ結合セル型リニアック、円盤装荷型リニアックにより212MeVに加速される。その第一段階として我々は2017年10月に世界初となるRFQによるミューオン加速実験に成功した。本発表では、ミューオンリニアックの設計と加速実験の結果について述べる。

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(13), p.132505_1 - 132505_5, 2018/03

AA2018-0124.pdf:0.62MB

 被引用回数:8 パーセンタイル:54.68(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

Characterization of the n_TOF EAR-2 neutron beam

Chen, Y. H.*; Tassan-Got, L.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他130名*

EPJ Web of Conferences, 146, p.03020_1 - 03020_4, 2017/09

 被引用回数:1 パーセンタイル:61.28

CERNの中性子飛行時間測定施設において、長い中性子飛行距離を有する第1実験室に加え、短い中性子飛行距離位置に第2実験室を設計・建設した。パラレル・プレート・アバランチェ・カウンター(PPAC)を用いて、第2実験室における中性子ビームの空間的広がり及びエネルギー分布を測定した。また、第1実験室で観測され時間校正に使用されてきた$$gamma$$線フラッシュは観測されないという知見が得られ、本観測結果に基づき、$$gamma$$線フラッシュの物理的起源に関する考察結果を示した。

論文

Time-of-flight and activation experiments on $$^{147}$$Pm and $$^{171}$$Tm for astrophysics

Guerrero, C.*; Lerendegui-Marco, J.*; Domingo-Pardo, C.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他113名*

EPJ Web of Conferences, 146, p.01007_1 - 01007_4, 2017/09

 被引用回数:1 パーセンタイル:61.28

The neutron capture cross section of several key unstable isotopes acting as branching points in the s-process are crucial for stellar nucleosynthesis studies, but they are very challenging to measure due to the difficult production of sufficient sample material, the high activity of the resulting samples, and the actual (n,$$gamma$$) measurement, for which high neutron fluxes and effective background rejection capabilities are required. Capture cross section of $$^{147}$$Pm and $$^{171}$$Tm have been measured for time-of-flight measurements at the CERN n_TOF facility using the 19 and 185m beam lines. Activation experiments on the same $$^{147}$$Pm and $$^{171}$$Tm targets with a high-intensity 30 keV quasi-Maxwellian flux of neutrons will be performed using the SARAF accelerator and the Liquid-Lithium Target (LiLiT) in order to extract the corresponding Maxwellian Average Cross Section (MACS). The status of these experiments and preliminary results will be presented and discussed as well.

論文

A New evaluation of the neutron data standards

Carlson, A. D.*; Pronyaev, V.*; Hale, G. M.*; Zhenpeng, C.*; Capote, R.*; Dur$'a$n, I.*; Hambsch, F.-J.*; 河野 俊彦*; 国枝 賢; 他13名*

EPJ Web of Conferences, 146, p.02025_1 - 02025_4, 2017/09

 被引用回数:4 パーセンタイル:90.94

近年測定された新しい断面積測定値を反映させることにより、IAEA標準核データである$$^1$$H(n,n), $$^6$$Li(n,t), $$^{10}$$B(n,$$alphagamma$$), $$^{10}$$B(n,$$alpha$$), C(n,n), $$^{197}$$Au(n,$$gamma$$), $$^{235}$$U(n,f)及び$$^{238}$$U(n,f)反応断面積の更新を行った。また、Au(n,$$gamma$$)反応断面積については、従来の標準核データに格納されていたデータを低エネルギー側へ拡張した。さらに、$$^{209}$$Biや$$^{238}$$U等に対する高エネルギー核分裂断面積、熱中性子反応による$$^{235}$$Uの核分裂中性子スペクトルや$$^{252}$$Cf自発核分裂中性子スペクトル等のデータを標準断面積に準じる参考値として整備した。

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

Observation of spin-dependent charge symmetry breaking in $$Lambda N$$ interaction; $$gamma$$-ray spectroscopy of $$^4_{Lambda}$$He

山本 剛史*; 長谷川 勝一; 早川 修平; 細見 健二; Hwang, S.; 市川 裕大; 今井 憲一; 金原 慎二; 中田 祥之; 佐甲 博之; et al.

Physical Review Letters, 115(22), p.222501_1 - 222501_5, 2015/11

AA2015-0707.pdf:0.5MB

 被引用回数:65 パーセンタイル:92.69(Physics, Multidisciplinary)

The energy spacing between the spin-doublet bound state of $$^4_{Lambda}$$He$$(1^+,0^+)$$ was determined to be $$1406 pm 2 pm 2$$ keV, by measuring $$gamma$$ rays for the $$1^+ to 0^+$$ transition with a high efficiency germanium detector array in coincidence with the $$^4{rm He}(K^-,pi^-)^4_{Lambda}$$He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus $$^4_{Lambda}$$H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in $$Lambda N$$ interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the $$0^+$$ ground state but is vanishingly small in the $$1^+$$ excited state, demonstrating that the $$Lambda N$$ CSB interaction has spin dependence.

報告書

第28回国際地質学会ワークショップ「放射性廃棄物処分における地質学的課題」要約

芦田 敬; 雨宮 清*; 新井 隆*; 他13名*

PNC TN8510 89-003, 34 Pages, 1989/10

PNC-TN8510-89-003.pdf:1.37MB

本報は,1989年7月9日$$sim$$19日に米国ワシントンで開催された第28回国際地質学会ワークショップ『放射性廃棄物処分における地質学的課題』における各国の報告のアブストラクト集を要約したものである。

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