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田中 翔也*; 廣瀬 健太郎; 西尾 勝久; Kean, K. R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; 有友 嘉浩*
Physical Review C, 105(2), p.L021602_1 - L021602_5, 2022/02
被引用回数:2 パーセンタイル:30.99(Physics, Nuclear)The angular momentum of a primary excited compound nucleus produced in multinucleon transfer reaction is an important quantity to evaluate cross sections to synthesize neutron-rich heavy element nuclei as well as for surrogate reaction studies. The mechanism is, however, not enough understood due to the lack of detailed experimental data. In the present study, we determined the angular momentum of primary excited nuclei, Np, Pu, and Am, produced in the multi-nucleon transfer channels of the O + Np reaction. With this aim, angular distributions of fission fragments with respect to the axis perpendicular to the reaction plane were measured for each compound nucleus. The distributions show an anisotropy exhibiting an enhanced yield on the reaction plane. They are well reproduced by a saddle point model, from which the average angular momentum is derived in the model framework. The angular momentum increases with the compound-nucleus mass, thus the number of nucleons exchanged, but shows a saturating trend toward heavier compound nuclei. These results are the first ones to point to the dependence of the angular momentum on the transfer channels.
Vermeulen, M. J.; 西尾 勝久; 廣瀬 健太郎; Kean, K. R.; 牧井 宏之; Orlandi, R.; 塚田 和明; Tsekhanovich, I.*; Andreyev, A. N.; 石崎 翔馬*; et al.
Physical Review C, 102(5), p.054610_1 - 054610_11, 2020/11
被引用回数:5 パーセンタイル:51.79(Physics, Nuclear)Fission fragment mass distributions for 23 nuclei (U, Np, Pu, Am, Cm, and Bk) were measured using the multi-nucleon transfer approach in the reaction of O+Np, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low energy fission of Np, Pu, and Cm is reported for the first time. The experimental data for all the studied nuclei were compared to the Langevin calculations. The calculation which takes into account the effects of multi-chance fission well reproduced the peak-to-valley ratio and mass-asymmetric peak positions of the distributions. The angular momenta given to the fissioning nucleus is also discussed.
Kean, K. R.; 西尾 勝久; 廣瀬 健太郎; Vermeulen, M. J.; 牧井 宏之; Orlandi, R.; 塚田 和明; Andreyev, A. N.; Tsekhanovich, I.*; 千葉 敏*
Physical Review C, 100(1), p.014611_1 - 014611_6, 2019/07
被引用回数:3 パーセンタイル:32.18(Physics, Nuclear)The validity of the multinucleon transfer (MNT) approach for deduction of fission barrier heights was investigated in an experiment carried out at the JAEA tandem accelerator facility. By using the O+Np reaction, fission barrier heights were inferred from fission probabilities of the nuclei Np and Pu produced in the and transfer channels, respectively. The deduced values of fission barriers agree well with the literature data, thus demonstrating the potential of the MNT reactions for obtaining fission-barrier data for nuclei not accessible for fission studies via neutron- or light charged particle-induced reactions.
Yakhshiev, U.*; Kim, H.-C.; 岡 眞
Physical Review D, 99(5), p.054027_1 - 054027_11, 2019/03
被引用回数:7 パーセンタイル:40.39(Astronomy & Astrophysics)磁場と結合させたカイラルラグランジアンにおけるスカーミオンの性質の変化を調べた。強い磁場のもとでスカーミオンが変形し、質量が増大することが明らかになり、そのメカニズムを考察した。さらにスカーミオンから導かれる核子とバリオンの性質を調べた。
橋本 直; 谷田 聖; 他67名*
Physics Letters B, 789, p.620 - 625, 2019/02
被引用回数:33 パーセンタイル:94.97(Astronomy & Astrophysics)における不変質量分布において、つまりが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。 = 350650MeV/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()に続いて残りの2各紙に吸収される反応()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 MeV、幅 MeV、そして波ガウス形状因子パラメータMeV/という値が""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。
Andreyev, A. N.; 西尾 勝久; Schmidt, K.-H.*
Reports on Progress in Physics, 81(1), p.016301_1 - 016301_61, 2018/01
被引用回数:127 パーセンタイル:91.67(Physics, Multidisciplinary)In the last two decades, through technological, experimental and theoretical advances, the situation in experimental fission studies has changed dramatically. With the use of advanced production and detection techniques both much more detailed and precise information can now be obtained for the traditional regions of fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies. This work first of all reviews the recent developments in experimental fission techniques, in particular the resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams. The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of the other fission observables, such as prompt neutron and -ray emission will also be reviewed. The review will conclude with the discussion of the new experimental fission facilities which are presently being brought into operation, along with promising "next-generation" fission approaches, which might become available within the next decade.
西尾 勝久; 千葉 敏*
日本原子力学会誌ATOMO, 59(12), p.717 - 721, 2017/12
核分裂は原子力エネルギー利用の基礎となる現象であるが、その複雑さのため質および量ともに限られた実験データを現象論によって記述し、核データとして利用されるにとどまっていた。近年、新規の実験技術確立に加え高性能計算機を活かした理論計算に大きな進展があったので、最新成果を見ながら議論する。
廣瀬 健太郎; 西尾 勝久; 田中 翔也*; Lguillon, R.*; 牧井 宏之; 西中 一朗*; Orlandi, R.; 塚田 和明; Smallcombe, J.*; Vermeulen, M. J.; et al.
Physical Review Letters, 119(22), p.222501_1 - 222501_6, 2017/12
被引用回数:50 パーセンタイル:91.17(Physics, Multidisciplinary)JAEAタンデム加速器施設で行ったO+U反応における多核子移行チャンネルを用いた実験により、U, Np、およびPuの核分裂質量分布を励起エネルギー1060MeVにおいて測定した。これらのうち、U, Npのデータは本実験により初めて観測された。原子核の殻効果の減衰によって対称分裂すると予想されていた高励起エネルギーにおいても、質量分布が非対称を示すことがわかった。搖動散逸定理に基づく動力学モデル計算との比較から、この振る舞いはマルチチャンス核分裂によるものであることを明らかにした。
西尾 勝久; 廣瀬 健太郎; Vermeulen, M. J.; 牧井 宏之; Orlandi, R.; 塚田 和明; 浅井 雅人; 豊嶋 厚史; 佐藤 哲也; 永目 諭一郎; et al.
EPJ Web of Conferences, 163, p.00041_1 - 00041_6, 2017/11
被引用回数:1 パーセンタイル:61.03(Nuclear Science & Technology)We are promoting a study of fission using multi-nucleon transfer (MNT) reactions, where excited states in neutron-rich actinide nuclei, which cannot be accessed by particle capture and/or fusion reactions, are populated. Also, the excited states in the fissioning nucleus are widely populated by the MNT reactions, from which effects of excitation energy on fission properties can be investigated. Experiments were carried out at the JAEA tandem facility in Tokai, Japan. We studied reactions using the O beam and several actinide target nuclei such as Th, U, Np, Cm. Ejectile nucleus was identified by a silicon E-E telescope to identify transfer channel and hence the compound nucleus. Fission fragments were detected by multi-wire proportional counters, and fission fragment mass distributions (FFMDs) were measured for each isotope. Measured FFMDs are reproduced by a calculation based on the fluctuation-dissipation model, and importance of multi-chance fission concept is investigated. Fission fragment angular distribution relative to the recoil direction suggested the increase of the spin of the fissioning nucleus with the number of transferred nucleons.
西尾 勝久; 廣瀬 健太郎; Lguillon, R.*; 牧井 宏之; Orlandi, R.; 塚田 和明; Smallcombe, J.*; 千葉 敏*; 有友 嘉浩*; 田中 翔也*; et al.
EPJ Web of Conferences, 146, p.04009_1 - 04009_6, 2017/09
被引用回数:3 パーセンタイル:86.09(Nuclear Science & Technology)The objective of this work is to extend fission data for actinide nuclei not investigated so far in order to understand the fission mechanism, especially for neutron-rich nuclei. Multi-nucleon transfer reactions were used to populate the compound nuclei which cannot be accessed by particle capture or fusion reactions. The experiment was carried out at the tandem facility of Japan Atomic Energy Agency. In the multi-nucleon transfer reactions using O beam, a wide variety of nuclei around a target nucleus was produced. By identifying transfer channels, fission data of nuclei more than fifteen compound nuclei were generated in one experiment. Another feature of transfer reaction is that the excitation energies of a compound nucleus can be populated continuously from the ground state up to several tens MeV, allowing us to study the excitation energy dependence of fission properties. From the excitation function of fission probabilities, fission-barrier heights of neutron-rich actinide nuclei were obtained. Experiments were carried out in the reactions of O + U, Th, Cm, Np. The obtained fission fragment mass distributions were reproduced by a model calculation based on a fluctuation dissipation model.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他431名*
Physical Review D, 95(11), p.112001_1 - 112001_15, 2017/06
被引用回数:17 パーセンタイル:63.32(Astronomy & Astrophysics)The cross section and transverse single-spin asymmetries of and from open heavy-flavor decays in polarized collisions at = 200 GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at = 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity () over the transverse momentum range of GeV/ for the cross section and GeV/ for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
Adare, A.*; 今井 憲一; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他328名*
Physical Review D, 94(11), p.112008_1 - 112008_10, 2016/12
被引用回数:9 パーセンタイル:42.15(Astronomy & Astrophysics)We report the double-helicity asymmetry, , in inclusive production at forward rapidity as a function of transverse momentum and rapidity . The data analyzed were taken during GeV longitudinally polarized collisions at the Relativistic Heavy Ion Collider in the 2013 run using the PHENIX detector. At this collision energy, particles are predominantly produced through gluon-gluon scatterings, thus is sensitive to the gluon polarization inside the proton. We measured by detecting the decay daughter muon pairs within the PHENIX muon spectrometers in the rapidity range . In this kinematic range, we measured the to be . The can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken : one at moderate range where recent data of jet and double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-x region Thus our new results could be used to further constrain the gluon polarization for .
Gade, A.*; Tostevin, J. A.*; Bader, V. M.*; Baugher, T.*; Bazin, D.*; Berryman, J. S.*; Brown, B. A.*; Hartley, D. J.*; Lunderberg, E.*; Recchia, F.*; et al.
Physical Review C, 93(3), p.031601_1 - 031601_5, 2016/03
被引用回数:15 パーセンタイル:72.2(Physics, Nuclear)中性子過剰カルシウム同位体では、最近、中性子数34の魔法数が発見されるなど、その殻構造が大きな注目を集めている。中性子の軌道の上には軌道があるはずであるが、これまでその位置に関する明確な実験データが存在しなかった。ミシガン州立大のサイクロトロン施設を用いて行われた本研究では、CaビームをCにあてる重イオン反応と脱励起線測定を組み合わせることによって、Caの4.018-MeV状態の分光学的因子を精度よく得ることに成功した。重イオン反応によって高角運動量状態の断面積を増大させ、脱励起線を測定することによって反応データだけでは分離できない状態を分離することが可能になったためである。この実験によって、4.018-MeV状態は比較的大きな分光学的因子を持つことがわかり、殻模型計算の予言が確かめられた。
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他445名*
Physical Review D, 93(5), p.051103_1 - 051103_8, 2016/03
被引用回数:25 パーセンタイル:73.27(Astronomy & Astrophysics)We present midrapidity measurements from the PHENIX experiment of large parity-violating single-spin asymmetries of high transverse momentum electrons and positrons from decays, produced in longitudinally polarized collisions at center of mass energies of = 500 and 510 GeV. These asymmetries allow direct access to the antiquark polarized parton distribution functions due to the parity-violating nature of the -boson coupling to quarks and antiquarks. The results presented are based on data collected in 2011, 2012, and 2013 with an integrated luminosity of 240 pb, which exceeds previous PHENIX published results by a factor of more than 27. These high data probe the parton structure of the proton at mass scale and provide an important addition to our understanding of the antiquark parton helicity distribution functions at an intermediate Bjorken value of roughly .
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他406名*
Physical Review D, 93(1), p.011501_1 - 011501_8, 2016/01
被引用回数:37 パーセンタイル:83.3(Astronomy & Astrophysics)PHENIX measurements are presented for the cross section and double-helicity asymmetry () in inclusive production at midrapidity from collisions at GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The results follow an increasingly positive asymmetry trend with and with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on and jet ALL and suggested a positive contribution of gluon polarization to the spin of the proton for the gluon momentum fraction range . The data presented here extend to a currently unexplored region, down to , and thus provide additional constraints on the value of .
Devaraja, H. M.*; Heinz, S.*; Beliuskina, O.*; Comas, V. F.*; Hofmann, S.*; Hornung, C.*; Mnzenberg, G.*; 西尾 勝久; Ackermann, D.*; Gambhir, Y. K.*; et al.
Physics Letters B, 748, p.199 - 203, 2015/09
被引用回数:66 パーセンタイル:96.96(Astronomy & Astrophysics)In deep inelastic multinucleon transfer reactions of Ca +Cm we observed about 100 residual nuclei with proton numbers between Z =82 and Z =100. Among them, there are five new neutron-deficient isotopes: U, Np, Am, Am and Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the -decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.
Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他574名*
Physical Review C, 91(3), p.031091_1 - 031091_8, 2015/03
被引用回数:44 パーセンタイル:93.39(Physics, Nuclear)The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment deviates from SM calculations by . Several theoretical models attribute this to the existence of a "dark photon", an additional gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, , in decays and obtained upper limits of O(2 on - mixing at 90% C.L. for the mass range . Combined with other experimental limits, the remaining region in the - mixing parameter space that can explain the deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of remaining.
今井 憲一; 谷田 聖; PHENIX Collaboration*
Physical Review D, 91(3), p.032001_1 - 032001_13, 2015/02
被引用回数:11 パーセンタイル:44.3(Astronomy & Astrophysics)We present midrapidity charged-pion invariant cross sections, the ratio of the to cross sections and the charge-separated double-spin asymmetries in polarized collisions at GeV. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The charge-separated pion asymmetries presented here sample an range of - and provide unique information on the sign of the gluon-helicity distribution.
Soukhovitskij, E. Sh.*; Capote, R.*; Quesada, J. M.*; 千葉 敏
Physical Review C, 72(2), p.024604_1 - 024604_12, 2005/08
被引用回数:67 パーセンタイル:94.74(Physics, Nuclear)非局所効果に起因する分散項を含むレーン型チャンネル結合模型を用いて、0.001200MeVの範囲でThによる核子散乱過程の研究を行った。分散項を考慮することで、エネルギー依存性の無い形状因子と簡単なエネルギー依存線を持つポテンシャル強度で測定データをよく再現できた。陽子チャンネルに対しては、クーロンバリア以下のエネルギー領域で分散項から来るクーロン補正が主要であることがわかった。また、核力の非局所性が要請する虚数ポテンシャルの振る舞いが、100MeV以上でデータを記述するうえで重要なことが判明した。
石井 哲朗; 重松 宗一郎; 浅井 雅人; 牧嶋 章泰*; 松田 誠; 金子 順一*; Hossain, I.*; 市川 進一; 河野 俊之*; 小川 雅生*
Physical Review C, 72(2), p.021301_1 - 021301_5, 2005/08
被引用回数:20 パーセンタイル:76.34(Physics, Nuclear)200MeVのOビームとU標的による2核子移行反応により、中性子過剰核であるUの脱励起線を測定した。Si -検出器を用いてO粒子と同時計測することにより、Uの線であることを同定した。O粒子の運動エネルギーの値を使い、Uの励起エネルギーを中性子分離エネルギー以下に限定した。Uにおいて、12状態までの基底バンドと9状態までのの8重極バンドを確立した。Uの8重極バンドヘッドは、Uのものよりも100keVほど高いエネルギーに位置する。このことは、U原子核の8重極相関が、中性子数144から146の領域で第2の極大値を持つことを示唆している。