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The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; 西尾 勝久; Lugaro, M.*; Li, Z. H.*; 牧井 宏之; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; 廣瀬 健太郎; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10


The long-lived $$^{60}$$Fe (with a half-life of 2.62 Myr) is a crucial diagnostic of active nucleosynthesis in the Milky Way galaxy and in supernovae near the solar system. The neutron-capture reaction $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe on $$^{59}$$Fe (half-life=44.5 days) is the key reaction for the production of $$^{60}$$Fe in massive stars. This reaction cross section has been previously constrained by the Coulomb dissociation experiment, which offered partial constraint on the E1 $$gamma$$-ray strength function but a negligible constraint on the M1 and E2 components. In this work, for the first time, we use the surrogate ratio method to experimentally determine the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross sections in which all the components are included. We derived a Maxwellian-averaged cross section of 27.5$$pm$$3.5 mb at $$kT$$ = 30 keV and 13.4$$pm$$1.7 mb at $$kT$$ = 90 keV, roughly 10%-20% higher than previous estimates. We analyzed the impact of our new reaction rates in nucleosynthesis models of massive stars and found that uncertainties in the production of $$^{60}$$Fe from the $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe rate are at most 25$$%$$. We conclude that stellar physics uncertainties now play a major role in the accurate evaluation of the stellar production of $$^{60}$$Fe.


Systematic study on the quark-hadron mixed phase in compact stars

Xia, C.-J.*; 丸山 敏毅; 安武 伸俊*; 巽 敏隆*; Shen, H.*; 富樫 甫*

Physical Review D, 102(2), p.023031_1 - 023031_18, 2020/07

 被引用回数:2 パーセンタイル:40.85(Astronomy & Astrophysics)



Multiple magnetic bilayers and unconventional criticality without frustration in BaCuSi$$_2$$O$$_6$$

Allenspach, S.*; Biffin, A.*; Stuhr, U.*; Tucker, G. S.*; 河村 聖子; 古府 麻衣子; Voneshen, D. J.*; Boehm, M.*; Normand, B.*; Laflorencie, N.*; et al.

Physical Review Letters, 124(17), p.177205_1 - 177205_7, 2020/05

 被引用回数:5 パーセンタイル:77.76(Physics, Multidisciplinary)

The dimerized quantum magnet BaCuSi$$_2$$O$$_6$$ was proposed as an example of "dimensional reduction" arising near the magnetic-field-induced quantum critical point (QCP) due to perfect geometrical frustration of its interbilayer interactions. We demonstrate by high-resolution neutron spectroscopy experiments that the effective intrabilayer interactions are ferromagnetic, thereby excluding frustration. We explain the apparent dimensional reduction by establishing the presence of three magnetically inequivalent bilayers, with ratios $$3 colon 2 colon 1$$, whose differing interaction parameters create an extra field-temperature scaling regime near the QCP with a nontrivial but nonuniversal exponent. We demonstrate by detailed quantum Monte Carlo simulations that the magnetic interaction parameters we deduce can account for all the measured properties of BaCuSi$$_2$$O$$_6$$, opening the way to a quantitative understanding of nonuniversal scaling in any modulated layered system.


Pre- and post-accident $$^{14}$$C activities in tree rings near the Fukushima Dai-ichi Nuclear Power Plant

松中 哲也*; 笹 公和*; 高橋 努*; 松村 万寿美*; 佐藤 志彦; Shen, H.*; 末木 啓介*; 松崎 浩之*

Radiocarbon, 61(6), p.1633 - 1642, 2019/12

 被引用回数:0 パーセンタイル:0.01(Geochemistry & Geophysics)

Areas affected by routine radiocarbon ($$^{14}$$C) discharges from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) and accidental releases in March 2011 were investigated by analysis of cores from Japanese cypress and cedar trees growing at sites 9 and 24 km northwest of the plant. $$^{14}$$C concentrations in tree rings from 2008-2014 (before and after the accident) were determined by accelerator mass spectrometry, with $$^{14}$$C activities in the range 231-256 Bq kg$$^{-1}$$ C. Activities during the period 2012-2014, after FDNPP shutdown, represent background levels, while the significantly higher levels recorded during 2008-2010, before the accident, indicate uptake of $$^{14}$$C from routine FDNPP operations. The mean excess $$^{14}$$C activity for the pre-accident period at the sites 9 and 24 km northwest of the plant were 21 and 12 Bq kg$$^{-1}$$ C, respectively, indicating that the area of influence during routine FDNPP operations extended at least 24 km northwest. The mean excess tree-ring $$^{14}$$C activities in 2011 were 10 and 5.8 Bq kg$$^{-1}$$ C at 9 and 24 km northwest, respectively, documenting possible impact of the FDNPP accident on $$^{14}$$C levels in trees.


Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

 被引用回数:2 パーセンタイル:35.62(Physics, Multidisciplinary)

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.


Radiocarbon variations in tree rings since 1960 near the Tokai nuclear facility, Japan

松中 哲也*; 笹 公和*; 高橋 努*; 細谷 青児*; 松村 万寿美*; 佐藤 志彦; Shen, H.*; 末木 啓介*

Nuclear Instruments and Methods in Physics Research B, 439, p.64 - 69, 2019/01

 被引用回数:2 パーセンタイル:42.44(Instruments & Instrumentation)



The $$^{95}$$Zr($$n, gamma$$)$$^{96}$$Zr cross section from the surrogate ratio method and its effect on $$s$$-process nucleosynthesis

Yan, S. Q.*; Li, Z. H.*; Wang, Y. B.*; 西尾 勝久; Lugaro, M.*; Karakas, A. I.*; 牧井 宏之; Mohr, P.*; Su, J.*; Li, Y. J.*; et al.

Astrophysical Journal, 848(2), p.98_1 - 98_8, 2017/10

 被引用回数:3 パーセンタイル:13.13(Astronomy & Astrophysics)

The $$^{95}$$Zr($$n, gamma$$)$$^{96}$$Zr reaction cross section is crucial in the modelling of $$s$$-process nucleosynthesis in asymptotic giant branch stars because it controls the operation of the branching point at the unstable $$^{95}$$Zr and the subsequent production of $$^{96}$$Zr. We have carried out the measurement of the $$^{90}$$Zr($$^{18}$$O,$$^{16}$$O) and $$^{94}$$Zr($$^{18}$$O,$$^{16}$$O) reactions and obtained the $$gamma$$-decay probability ratio of $$^{92}$$Zr$$^{*}$$ and $$^{96}$$Zr$$^{*}$$ to determine the $$^{95}$$Zr($$n, gamma$$)$$^{96}$$Zr reaction cross sections with the surrogate ratio method. We tested our deduced maxwellian-averaged cross section in stellar models with masses between 2 and 6 $$M_{odot}$$ and metallicities 0.014 and 0.03. The largest changes - up 80 % variations in $$^{96}$$Zr - are seen in the models of 3-4 $$M_{odot}$$, where the $$^{22}$$Ne neutron source is mildly activated. The new rate can still provide a match to data from meteoritic stardust silicon carbide grains, provided the maximum mass of the parent stars is below 4 $$M_{odot}$$, for a metallicity of 0.03.


Self-learning Monte Carlo method; Continuous-time algorithm

永井 佑紀; Shen, H.*; Qi, Y.*; Liu, J.*; Fu, L.*

Physical Review B, 96(16), p.161102_1 - 161102_6, 2017/10

 被引用回数:43 パーセンタイル:91.96(Materials Science, Multidisciplinary)



Examination of the surrogate ratio method for the determination of the $$^{93}$$Zr(n,$$gamma$$)$$^{94}$$Zr cross section with $$^{90,92}$$Zr($$^{18}$$O,$$^{16}$$O)$$^{92,94}$$Zr reactions

Yan, S. Q.*; Li, Z. H.*; Wang, Y. B.*; 西尾 勝久; 牧井 宏之; Su, J.*; Li, Y. J.*; 西中 一朗; 廣瀬 健太郎; Han, Y. L.*; et al.

Physical Review C, 94(1), p.015804_1 - 015804_5, 2016/07

 被引用回数:5 パーセンタイル:40.15(Physics, Nuclear)

The relative $$gamma$$-decay probability ratios of the neutron resonance states in $$^{94}$$Zr and $$^{92}$$Zr populated via two neutron transfer reactions, $$^{92}$$Zr($$^{18}$$O,$$^{16}$$O)$$^{94}$$Zr and $$^{90}$$Zr($$^{18}$$O,$$^{16}$$O)$$^{92}$$Zr, have been measured to test the validity of the surrogate ratio method (SRM) in determining the (n,$$gamma$$) reaction cross section. The cross sections of the $$^{93}$$Zr(n,$$gamma$$)$$^{94}$$Zr reaction are derived from the experimentally obtained ratios and the cross sections of the $$^{91}$$Zr(n,$$gamma$$)$$^{92}$$Zr reaction in the equivalent neutron energy range of $$E_{rm n}$$ = 0 - 8 MeV. The deduced cross sections of $$^{93}$$Zr(n,$$gamma$$)$$^{94}$$Zr reaction agree with the directly measured ones in the low-energy region, and with the evaluated ENDF/B-VII.1 data at higher energies of $$E_{rm n} >$$ 3 MeV. The agreement supports the concept of the SRM method to indirectly determine the (n,$$gamma$$) reaction cross sections.


Carrier-mediated ferromagnetism in the magnetic topological insulator Cr-doped (Sb,Bi)$$_{2}$$Te$$_{3}$$

Ye, M.*; Li, W.*; Zhu, S.-Y.*; 竹田 幸治; 斎藤 祐児; Wang, J.*; Pan, H.*; Nurmamat, M.*; 角田 一樹*; Ji, F.*; et al.

Nature Communications (Internet), 6, p.8913_1 - 8913_7, 2015/11


 被引用回数:43 パーセンタイル:90.62(Multidisciplinary Sciences)



Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids

Althammer, M.*; Meyer, S.*; 中山 裕康*; Schreier, M.*; Altmannshofer, S.*; Weiler, M.*; Huebl, H.*; Gepr$"a$gs, S.*; Opel, M.*; Gross, R.*; et al.

Physical Review B, 87(22), p.224401_1 - 224401_15, 2013/06

 被引用回数:330 パーセンタイル:99.39(Materials Science, Multidisciplinary)

強磁性絶縁体/Ptと強磁性絶縁体/常磁性金属/Pt複合素子において、スピンHall磁気抵抗効果の定量測定を行った。強磁性絶縁体にはイットリウム鉄ガーネット,ニッケルフェライト,マグネタイトを用い、常磁性中間層には銅、金を用いた。以上により、薄い中間層にかかわらず、Pt層のスピンHall効果と逆スピンHall効果の複合によって強磁性層の磁化方向に依存した磁気抵抗効果が生じるというスピンHall磁気抵抗効果の理論の正当性が実験的に確認された。スピンHall磁気抵抗効果の理論を援用することで、4$$times10^{14}Omega^{-1}$$m$$^{-2}$$のスピンミキシングコンダクタンスを持つサンプルに対して、PtのスピンHall角とスピン拡散長がそれぞれ、$$0.11pm0.08, 1.5pm0.5$$nmと得られた。


Angle-resolved photoemission spectroscopy study of PrFeAsO$$_{0.7}$$; Comparison with LaFePO

西 一郎*; 石角 元志; 出田 真一郎*; Malaeb, W.*; 吉田 鉄平*; 藤森 淳*; 小谷 佳範*; 久保田 正人*; 小野 寛太*; Yi, M.*; et al.

Physical Review B, 84(1), p.014504_1 - 014504_5, 2011/07

 被引用回数:20 パーセンタイル:66.65(Materials Science, Multidisciplinary)



From a single-band metal to a high-temperature superconductor via two thermal phase transitions

He, R.-H.*; 橋本 真*; Karapetyan, H.*; Koralek, J. D.*; Hinton, J. P.*; Testaud, J. P.*; Nathan, V.*; 吉田 良行*; Yao, H.*; 田中 清尚*; et al.

Science, 331(6024), p.1579 - 1583, 2011/03

 被引用回数:252 パーセンタイル:98.82(Multidisciplinary Sciences)



Postbounce evolution of core-collapse supernovae; Long-term effects of the equation of state

住吉 光介*; 山田 章一*; 鈴木 英之*; Shen, H.*; 千葉 敏; 土岐 博*

Astrophysical Journal, 629(2, Part1), p.922 - 932, 2005/08

 被引用回数:211 パーセンタイル:97.46(Astronomy & Astrophysics)



Self-learning continuous-time quantum Monte Carlo method

永井 佑紀; Shen, H.*; Qi, Y.*; Liu, J.*; Fu, L.*

no journal, , 



自己学習連続時間量子モンテカルロ法; 機械学習を用いたマルコフ連鎖モンテカルロ法の高速化

永井 佑紀; Shen, H.*; Qi, Y.*; Liu, J.*; Fu, L.*

no journal, , 




永井 佑紀; Shen, H.*; Qi, Y.*; Liu, J.*; Fu, L.*

no journal, , 


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