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論文

Simultaneous determination of neutron-induced fission and radiative capture cross sections from decay probabilities obtained with a surrogate reaction

P$'e$rez S$'a$nchez, R.*; Jurado, B.*; M$'e$ot, V.*; Roig, O.*; Dupuis, M.*; Bouland, O.*; Denis-Petit, D.*; Marini, P.*; Mathieu, L.*; Tsekhanovich, I.*; et al.

Physical Review Letters, 125(12), p.122502_1 - 122502_5, 2020/09

Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of $$^{239}$$Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and $$gamma$$-emission probabilities for the $$^{240}$$Pu($$^{4}$$He, $$^{4}$$He') surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected $$gamma$$-ray transitions, we measure the $$gamma$$-emission probability. This enlarges the applicability of the surrogate-reaction method.

論文

Sequential nature of ($$p,3p$$) two-proton knockout from neutron-rich nuclei

Frotscher, A.*; G$'o$mez-Ramos, M.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Orlandi, R.; 他86名*

Physical Review Letters, 125(1), p.012501_1 - 012501_7, 2020/07

Twenty-one two-proton ($$p,3p$$) knock-out cross sections of neutron-rich radioactive isotopes were measured in inverse kinematics using the MINOS time-projection chamber at RIBF, RIKEN. The proton angular distributions, measured for the first time, reveal that the reaction kinematics of the ($$p,3p$$) reaction is consistent with sequential proton collisions within the projectile nucleus.

論文

In-source laser spectroscopy of dysprosium isotopes at the ISOLDE-RILIS

Chrysalidis, K.*; Barzakh, A. E.*; Ahmed, R.*; Andreyev, A. N.; Ballof, J.*; Cubiss, J. G.*; Fedorov, D. V.*; Fedosseev, V. N.*; Fraile, L. M.*; Harding, R. D.*; et al.

Nuclear Instruments and Methods in Physics Research B, 463, p.472 - 475, 2020/01

 被引用回数:0 パーセンタイル:100(Instruments & Instrumentation)

放射壊変によって生成された多数のジスプロシウム同位体について、ISOLDEのレーザー共鳴イオン源(RILIS)を用いてイオン源内レーザー分光法によって研究した。$$^{152}$$Dyに対する相対的な同位体シフトを$$4f^{10}6s^{2}~^{5}I_{8}$$ (gs) $$rightarrow$$ $$4f^{10}6s6p~(8,1)^{o}_{8}$$共鳴遷移を用いて測定した。電子的因子Fとマスシフト因子Mを導出し、それらを使って$$^{rm 145m}$$Dyと$$^{rm 147m}$$Dyの平均自乗荷電半径の変化を初めて決定した。

論文

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes; Coulomb excitation of $$^{182}$$Hg, $$^{184}$$Hg, $$^{186}$$Hg and $$^{188}$$Hg

Wrzosek-Lipska, K.*; Rezynkina, K.*; Bree, N.*; Zieli$'n$ska, M.*; Gaffney, L. P.*; Petts, A.*; Andreyev, A. N.; Bastin, B.*; Bender, M.*; Blazhev, A.*; et al.

European Physical Journal A, 55(8), p.130_1 - 130_23, 2019/08

 被引用回数:5 パーセンタイル:14.53(Physics, Nuclear)

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass $$^{182-188}$$Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0$$^{+}_{1,2}$$, 2$$^{+}_{1,2}$$, and 4$$^{+}_{1}$$ states was observed in all nuclei under study. Reduced $$E2$$ matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.

論文

Theoretical analysis on the $$K^{-3}$$He $$rightarrow Lambda pn$$ reaction for the $$bar{K} N N$$ bound-state search in the J-PARC E15 experiment

関原 隆泰; Oset, E.*; Ramos, A.*

Proceedings of Science (Internet), 310, 5 Pages, 2018/03

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-} p p$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

論文

What makes the peak structure of the $$Lambda p$$ invariant-mass spectrum in the $$K^{-3} rm He rightarrow Lambda$$$$pn$$ reaction?

関原 隆泰; Oset, E.*; Ramos, A.*

Acta Physica Polonica B, 48(10), p.1869 - 1874, 2017/10

 被引用回数:1 パーセンタイル:80.24(Physics, Multidisciplinary)

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-}pp$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

論文

Temperature dependence of the spin Seebeck effect in [Fe$$_{3}$$O$$_{4}$$/Pt]n multilayers

Ramos, R.*; 吉川 貴史*; Anad$'o$n, A.*; Lucas, I.*; 内田 健一*; Algarabel, P. A.*; Morell$'o$n, L.*; Aguirre, M. H.*; 齊藤 英治; Ibarra, M. R.*

AIP Advances (Internet), 7(5), p.055915_1 - 055915_7, 2017/05

 被引用回数:13 パーセンタイル:24.22(Nanoscience & Nanotechnology)

We report temperature dependent measurements of the spin Seebeck effect (SSE) in multilayers formed by repeated growth of a Fe$$_3$$O$$_4$$/Pt bilayer junction. The magnitude of the observed enhancement of the SSE, relative to the SSE in the single bilayer, shows a monotonic increase with decreasing the temperature. This result can be understood by an increase of the characteristic length for spin current transport in the system, in qualitative agreement with the recently observed increase in the magnon diffusion length in Fe$$_3$$O$$_4$$ at lower temperatures. Our result suggests that the thermoelectric performance of the SSE in multilayer structures can be further improved by careful choice of materials with suitable spin transport properties.

論文

The Peak structure in the in-flight $$^{3}$$He$$(K^{-}, Lambda p) n$$ reaction around the $$bar{K} N N$$ Threshold

関原 隆泰; Oset, E.*; Ramos, A.*

JPS Conference Proceedings (Internet), 13, p.020002_1 - 020002_5, 2017/02

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-} p p$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

論文

On the structure observed in the in-flight $$^{3}$$He($$K^{-}, Lambda p)n$$ reaction at J-PARC

関原 隆泰; Oset, E.*; Ramos, A.*

Progress of Theoretical and Experimental Physics (Internet), 2016(12), p.123D03_1 - 123D03_27, 2016/12

AA2016-0237.pdf:1.53MB

 被引用回数:24 パーセンタイル:12.14(Physics, Multidisciplinary)

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment of the in-flight $$^{3}$$He($$K^{-}, Lambda p)n$$ reaction at J-PARC, which could be a signal of the lightest kaonic nuclei, that is, the $$bar{K} N N (I=1/2)$$ state. For the investigation, we evaluate the $$Lambda p$$ invariant mass spectrum assuming two possible scenarios to interpret the experimental peak. One assumes that the $$Lambda(1405)$$ resonance is generated after the emission of an energetic neutron from the absorption of the initial $$K^-$$, not forming a bound state with the remaining proton. The other scenario implies that, after the emission of the energetic neutron, a $$bar{K} N N$$ bound state is formed. Our results show that the experimental signal observed in the in-flight $$^{3}$$He($$K^{-}, Lambda p)n$$ reaction at J-PARC is qualitatively well reproduced by the assumption that a $$bar{K} N N$$ bound state is generated in the reaction, definitely discarding the interpretation in terms of an uncorrelated $$Lambda (1405) p$$ state.

論文

Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

Ramos, R.*; 吉川 貴史*; Aguirre, M.*; Lucas, I.*; Anad$'o$n, A.*; 小宅 教文*; 内田 健一*; 安立 裕人; 塩見 淳一郎*; Algarabel, P. A.*; et al.

Physical Review B, 92(22), p.220407_1 - 220407_5, 2015/12

 被引用回数:47 パーセンタイル:8.47(Materials Science, Multidisciplinary)

Spin Seebeck effects have been investigated in highly crystalline magnetic multilayer films. Voltage as well as power generated by the spin Seebeck effect were found to be significantly enhanced with increasing the number of layers, $$n$$. This voltage enhancement defies the simple understanding of the spin Seebeck effect and suggests that spin current flowing between the magnetic layers in the thickness direction plays an important role in the multilayer SSE systems and the observed voltage enhancement.

論文

Anomalous Nernst effect of Fe$$_{3}$$O$$_{4}$$ single crystal

Ramos, R.*; Aguirre, M. H.*; Anad$'o$n, A.*; Blasco, J.*; Lucas, I.*; 内田 健一*; Algarabel, P. A.*; Morell$'o$n, L.*; 齊藤 英治; Ibarra, M. R.*

Physical Review B, 90(5), p.054422_1 - 054422_6, 2014/08

 被引用回数:46 パーセンタイル:9.27(Materials Science, Multidisciplinary)

We report a complete characterization of the anomalous Nernst effect (ANE) and its relationship with the anomalous Hall effect (AHE) in Fe$$_{3}$$O$$_{4}$$. By combining full thermoelectric and electric transport measurements as a function of temperature, we have verified that the universal scaling relation between the anomalous Hall and diagonal conductivities, observed in materials with bad-metal-hopping type of conduction, is also applicable to the thermoelectric transport. We further show that the ANE and AHE are commonly related through the Mott relation, therefore demonstrating its validity for anomalous transport phenomena in materials with conduction in the dirty regime.

論文

Observation of the spin Seebeck effect in epitaxial Fe$$_{3}$$O$$_{4}$$ thin films

Ramos, R.*; 吉川 貴史*; 内田 健一*; 安立 裕人; Lucas, I.*; Aguirre, M.*; Algarabel, P.*; Morell$'o$n, L.*; 前川 禎通; 齊藤 英治; et al.

Applied Physics Letters, 102(7), p.072413_1 - 072413_5, 2013/02

 被引用回数:120 パーセンタイル:2.44(Physics, Applied)

We report the experimental observation of the spin Seebeck effect in magnetite thin films. The signal observed at temperatures above the Verwey transition is a contribution from both the anomalous Nernst (ANE) and spin Seebeck (SSE) effects. The contribution from the ANE of the Fe$$_{3}$$O$$_{4}$$ layer to the SSE is found to be negligible due to the resistivity difference between Fe$$_{3}$$O$$_{4}$$ and Pt layers. Below the Verwey transition, the SSE is free from the ANE of the ferromagnetic layer and it is also found to dominate over the ANE due to magnetic proximity effect on the Pt layer.

口頭

On the structure observed in the in-flight $$^{3}$$He$$(K^{-}, Lambda p)n$$ reaction at J-PARC

関原 隆泰; Oset, E.*; Ramos, A.*

no journal, , 

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-} p p$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

口頭

On the structure observed in the in-flight $$^{3}$$He($$K^{-}, Lambda p)n$$ reaction at J-PARC

関原 隆泰; Oset, E.*; Ramos, A.*

no journal, , 

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-} p p$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

口頭

On the structure observed in the in-flight $$^{3}$$He($$K^{-}, Lambda p)n$$ reaction at J-PARC

関原 隆泰; Oset, E.*; Ramos, A.*

no journal, , 

In this contribution we theoretically investigate what is the origin of the peak structure observed in the E15 experiment at J-PARC. Since the peak exists near the $$K^{-} p p$$ threshold, we expect two scenarios to produce the peak. One is that the $$Lambda (1405)$$ is generated but it does not correlate with $$p$$, and the uncorrelated $$Lambda (1405)$$-$$p$$ system subsequently decays into $$Lambda p$$. The other is that the $$bar{K} N N$$ quasi-bound state is indeed generated and decays into $$Lambda p$$. We calculate the $$Lambda p$$ invariant mass spectrum of the reaction with these two scenarios and compare it with the experimental one to interpret the experimental peak structure.

口頭

Benchmarking reaction theories for nucleon knockout reactions

吉田 数貴; Moro, A.*; 緒方 一介*; G$'o$mez-Ramos, M.*

no journal, , 

原子核の核分光学に有用な手法として、陽子による核子ノックアウト反応、すなわち(p,pN)反応がある。この反応を記述する反応理論として、歪曲波インパルス近似、Transfer-to-the-continuum模型、そしてFaddeev/AGS法を取り上げ、これらの反応理論計算が、核子あたり420MeVの入射エネルギーでの$$^{15}$$C(p,pn)$$^{14}$$C反応に対して一致し、十分な整合性をもつことを確認した。また、相対論的補正の必要性や、光学ポテンシャルのエネルギー依存性からくる不定性についても調査した。

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