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論文

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

大場 洋次郎; 足立 望*; 戸高 義一*; Gilbert, E. P.*; 間宮 広明*

Physical Review Research (Internet), 2(3), p.033473_1 - 033473_6, 2020/11

Formation of nanosized spin misalignment was found in pure iron processed by high-pressure torsion straining. The small-angle neutron scattering profiles show that the spin misalignment remains in magnetic field up to 10 T, whereas the magnetization is almost saturated below 1 T based on the magnetic measurement. These results indicates that anomalous magnetic anisotropy is induced in pure iron via the high-pressure torsion straining.

論文

Optomagnonic Barnett effect

仲田 光樹; 高吉 慎太郎*

Physical Review B, 102(9), p.094417_1 - 094417_11, 2020/09

 被引用回数:0

いわゆる光学的Barnett効果[A. Rebei and J. Hohlfeld, Phys. Lett. A 372, 1915 (2008); J. Appl. Phys. 103, 07B118 (2008)], i.e., 円偏光レーザー誘起磁化成長[S. Takayoshi et al., Phys. Rev. B 90, 214413 (2014); S. Takayoshi et al., Phys. Rev. B 90, 085150 (2014)]をフェリ磁性絶縁体に応用し、THz領域におけるマグノン凝縮機構を微視的に解明した。これはBose統計に従うマグノンに特有の巨視的量子効果である。本研究が提供するTHzマグノン凝縮体を活用することで、従来の強磁性絶縁体中のものよりはるかに高速のスピン輸送「巨視的量子干渉効果によるJosephsonスピン流」を実現することができる。

論文

Direct measurement of fast ortho-para conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210)

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

Physical Review B, 102(12), p.121407_1 - 121407-5, 2020/09

Pd(210)表面に化学吸着したH$$_{2}$$のオルトーパラ転換を報告する。分子線,光刺激脱離,共鳴多光子イオン化法を用いて水素の回転状態変化を調べた。実験結果から、~2秒の転換時間で転換が起こることが明らかになった。実験結果と過去の理論計算結果を比較することで、2次の摂動による転換メカニズムを支持する。

論文

Theoretical study of Nb isotope productions by muon capture reaction on $$^{100}$$Mo

Ciccarelli, M.*; 湊 太志; 内藤 智也*

Physical Review C, 102, p.034306_1 - 034306_9, 2020/09

The isotope $$^{99}$$Mo, the generator of $$^{rm 99m}$$Tc used for diagnostic imaging, is supplied by extracting from fission fragments of highly enriched uranium in reactors. However, a reactor-free production method of $$^{99}$$Mo is searched over the world from the point of view of nuclear proliferation. Recently, $${}^{99}$$Mo production through a muon capture reaction was proposed and it was found that about 50% of $$^{100}$$Mo turned into $$^{99}$$Mo through $$^{100}$$Mo$$(mu^-,n)$$ reaction. However, the detailed physical process of the muon capture reaction is not completely understood. We, therefore, study the muon capture reaction of $$^{100}$$Mo by a theoretical approach. We used the $$pn$$ QRPA to calculate the muon capture rate. The muon wave function is calculated with considering the electronic distribution of the atom and the nuclear charge distribution. The particle evaporation process from the daughter nucleus is calculated by the Hauser-Feshbach statistical model. From the model calculation, about 38% of $$^{100}$$Mo is converted to $$^{99}$$Mo through the muon capture reaction, which is in a reasonable agreement with the experimental data. It is revealed that negative parity states, especially $$ 1^- $$ state, play an important role in $$^{100}$$Mo $$(mu^-,n)^{99}$$Nb. Isotope production by the muon capture reaction strongly depends on the nuclear structure. To understand the mechanism, excitation energy functions have to be known microscopically.

論文

Charmed baryon spectrum from lattice QCD near the physical point

Bahtiyar, H.*; Can, K. U.*; Erkol, G.*; Gubler, P.; 岡 眞; 高橋 徹*

Physical Review D, 102(5), p.054513_1 - 054513_18, 2020/09

格子QCDによる第一原理計算を用いて、正負パリティのチャームバリオンの基底および励起状態のスペクトルを求めた。チャームクォークを1個, 2個あるいは3個含むバリオンの正および負パリティ状態の質量を、第一原理計算から求めることで、これまでの実験データや模型計算結果との比較を行い、その物理的な意味を解析することが可能となる。今回の計算では、パイオンの質量が観測値に十分近い物理点に近い領域で、2+1フレーバーのゲージ配位を用いた解析を行った。ディラック行列などの配置の異なる複数の演算子を用意し、その交差相関関数を計算し、固有値を求める方法により、基底状態と励起状態のスペクトルを計算した。

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

Unveiling spin-dependent unoccupied electronic states of Co$$_{2}$$MnGe (Ga) film via Ge (Ga) $$L_{2,3}$$ absorption spectroscopy

吉川 智己*; Antonov, V. N.*; 河野 嵩*; 鹿子木 将明*; 角田 一樹; 宮本 幸治*; 竹田 幸治; 斎藤 祐児; 後藤 一希*; 桜庭 裕弥*; et al.

Physical Review B, 102(6), p.064428_1 - 064428_7, 2020/08

 被引用回数:0

X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy were applied at the Ge (Ga) $$L_{2,3}$$ edge to unravel the spin-resolved unoccupied electronic states of Co$$_{2}$$MnGe (Ga). Complicated spectral features were observed in both XAS and XMCD spectra. For their interpretation, we compared the experimental XAS and XMCD spectra with the calculated Ge (Ga) 4$$s$$ and 4$$d$$ orbital partial density of states. The comparison enabled a qualitative explanation of the XMCD spectra as the difference between the majority and minority-spin unoccupied density of states summed over the 4$$s$$ and 4$$d$$ orbitals. Our finding provides a new approach to uncover the spin-split partial density of states above the Fermi level.

論文

Signatures of the vortical quark-gluon plasma in hadron yields

田屋 英俊*; Park, A.*; Cho, S.*; Gubler, P.; 服部 恒一*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; 門内 明彦*; 大西 明*; et al.

Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08

 被引用回数:0 パーセンタイル:100(Physics, Nuclear)

We investigate the hadron production from the vortical quark-gluon plasma created in heavy-ion collisions. Based on the quark-coalescence and statistical hadronization models, we show that total hadron yields summed over the spin components are enhanced by the local vorticity with quadratic dependence. The enhancement factor amounts to be a few percent and may be detectable within current experimental sensitivities. We also show that the effect is stronger for hadrons with larger spin, and thus propose a new signature of the local vorticity, which may be detected by the yield ratio of distinct hadron species having different spins such as $$phi$$ and $$eta'$$. The vorticity dependence of hadron yields seems robust, with consistent predictions in both of the hadron production mechanisms for reasonable values of the vorticity strength estimated for heavy-ion collisions.

論文

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

羽場 宏光*; Fan, F.*; 加治 大哉*; 笠松 良崇*; 菊永 英寿*; 小森 有希子*; 近藤 成美*; 工藤 久昭*; 森本 幸司*; 森田 浩介*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

 被引用回数:0

The nuclide $$^{266}$$Bh was produced in the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of $$^{266}$$Bh were investigated with a rotating wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. The half-life of $$^{266}$$Bh was measured to be $$T_{rm 1/2}$$ = 10.0$$^{+2.6}_{-1.7}$$ s. The $$alpha$$-particle energies of $$^{266}$$Bh disperse widely in the range of 8.62 - 9.40 MeV. The maximum production cross section for the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction was determined to be $$sigma$$ = 57 $$pm$$ 14 pb at 130.6 MeV.

論文

Decay studies of the long-lived states in $$^{186}$$Tl

Stryjczyk, M.*; Andel, B.*; Andreyev, A. N.; Cubiss, J.*; Pakarinen, J.*; 他43名*

Physical Review C, 102(2), p.024322_1 - 024322_9, 2020/08

Decay spectroscopy of the long-lived states in $$^{186}$$Tl has been performed at ISOLDE, CERN. The $$alpha$$ decay from the low-spin (2$$^{-}$$) state in $$^{186}$$Tl was observed for the first time and a half-life was determined. Based on the $$alpha$$-decay energy, the relative positions of the long-lived states were fixed, with the (2$$^{-}$$) state as the ground state, the 7$$^{(+)}$$ state at 77(56) keV, and the 10$$^{(-)}$$ state at 451(56) keV. The level scheme of the internal decay of the $$^{186}$$Tl(10$$^{(-)}$$) state, which was known to decay solely through emission of 374-keV $$gamma$$-ray transition, was extended and a lower limit for the $$beta$$-decay branching b$$_{beta}$$ $$>$$ 5.9(3)% was determined. The extracted retardation factors for the $$gamma$$ decay of the 10$$^{(-)}$$ state were compared to the available data in neighboring odd-odd thallium isotopes indicating the importance of the $$pi$$d$$_{3/2}$$ shell in the isomeric decay and significant structure differences between $$^{184}$$Tl and $$^{186}$$Tl.

論文

Enhancement of domain-wall mobility detected by NMR at the angular momentum compensation temperature

今井 正樹; 中堂 博之; 松尾 衛; 前川 禎通; 齊藤 英治

Physical Review B, 102(1), p.014407_1 - 014407_5, 2020/07

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

The angular momentum compensation temperature $$T_{rm A}$$ of ferrimagnets has attracted much attention because of high-speed magnetic dynamics near $$T_{rm A}$$. We show that NMR can be used to investigate domain wall dynamics near $$T_{rm A}$$ in ferrimagnets. We performed $$^{57}$$Fe-NMR measurements on the ferrimagnet Ho$$_3$$Fe$$_5$$O$$_{12}$$ with $$T_{rm A}$$ = 245 K. In a multi-domain state, the NMR signal is enhanced by domain wall motion. We found that the NMR signal enhancement shows a maximum at $$T_{rm A}$$ in the multi-domain state. The NMR signal enhancement occurs due to increasing domain-wall mobility toward $$T_{rm A}$$. We develop the NMR signal enhancement model involves domain-wall mobility. Our study shows that NMR in multi-domain state is a powerful tool to determine $$T_{rm A}$$, even from a powder sample and it expands the possibility of searching for angular momentum-compensated materials.

論文

Self-learning hybrid Monte Carlo; A First-principles approach

永井 佑紀; 奥村 雅彦; 小林 恵太*; 志賀 基之

Physical Review B, 102(4), p.041124_1 - 041124_6, 2020/07

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

第一原理計算で得られたポテンシャルを再現するようなニューラルネットワーク(ANN)を構築して分子動力学を実行するのが機械学習分子動力学法である。ANNを構築する際の最適なトレーニングデータは、元々の第一原理分子動力学法で生成される原子配置とそのポテンシャルである。通常は、様々な原子配置とそのポテンシャルデータを大量に作成することで、目的の機械学習分子動力学法と同じようなポテンシャルを生成するANNを構築している。しかしながら、構築されたANNが元々の第一原理計算のポテンシャルを再現するという保証はない。さらに、4元素以上で構成されるような系の場合には、長時間の機械学習分子動力学法では計算が不安定になることがあり、機械学習分子動力学法の計算の精度や妥当性については常に慎重な議論が必要であった。本論文発表では、自己学習モンテカルロ法のアイディアを用いることで、得られた結果が統計的に厳密にオリジナルの第一原理計算分子動力学法の計算結果と等しい手法を開発したことを報告する。

論文

Measurement of $$J/psi$$ at forward and backward rapidity in $$p$$+$$p$$, $$p$$$$+A$$l, $$p$$$$+A$$u, and $$^3$$He+Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他358名*

Physical Review C, 102(1), p.014902_1 - 014902_23, 2020/07

 被引用回数:0 パーセンタイル:100(Physics, Nuclear)

Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of harmonium in small systems have become increasingly relevant. We present the results of $$J/psi$$ measurements at forward and backward rapidity in various small collision systems, $$p$$$$+$$$$p$$, $$p$$$$+$$Al, $$p$$$$+$$Au and $$^3$$He$$+$$Au, at $$sqrt{s_{_{NN}}}$$=200 GeV. The results are presented in the form of the observable $$R_{AB}$$, the nuclear modification factor, a measure of the ratio of the $$J/psi$$ invariant yield compared to the scaled yield in $$p$$$$+$$$$p$$ collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on $$J/psi$$ production with different projectile sizes $$p$$ and $$^3$$He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for $$p$$$$+$$Au and $$^{3}$$He$$+$$Au. However, for 0% - 20% central collisions at backward rapidity, the modification for $$^{3}$$He$$+$$Au is found to be smaller than that for $$p$$$$+$$Au, with a mean fit to the ratio of $$0.89pm0.03$$(stat)$${pm}0.08$$(syst), possibly indicating final state effects due to the larger projectile size.

論文

Transition strengths in the neutron-rich $$^{73,74,75}$$Ni isotopes

Gottardo, A.*; de Angelis, G.*; Doornenbal, P.*; Coraggio, L.*; Gargano, A.*; Itaco, N.*; Orlandi, R.; 他52名*

Physical Review C, 102(1), p.014323_1 - 014323_8, 2020/07

Reduced transition probabilities have been measured for the neutron-rich $$^{73,74,75}$$Ni nuclei with relativistic Coulomb excitation performed at the RIKEN Nishina Center. Excitation energies compare well with the result of large-scale shell-model calculations, while $$B(E2)$$ values are larger than predicted. This could indicate an increasing contribution of proton excitations across the $$Z=28$$ shell closure when approaching $$^{78}$$Ni.

論文

$$beta$$-delayed fission of isomers in $$^{188}$$Bi

Andel, B.*; Andreyev, A. N.; Antalic, S.*; Al Monthery, M.*; Barzakh, A.*; Bissell, M. L.*; Chrysalidis, K.*; 他29名*

Physical Review C, 102(1), p.014319_1 - 014319_12, 2020/07

$$beta$$-delayed fission ($$beta$$DF) decay of a low-spin (ls) and a high-spin (hs) isomer in $$^{188}$$Bi was studied at the ISOLDE facility at CERN. Their $$beta$$DF partial half-lives were determined: $$T_{rm 1/2p}$$, $$beta$$DF($$^{188}$$Bi$$^{hs}$$)= 5.6(8) $$times$$ 10$$^{3}$$ s and $$T_{rm 1/2p}$$, $$beta$$DF($$^{188}$$Bi$$^{ls}$$)=1.7(6) $$times$$ 10$$^{3}$$ s. This work is the first $$beta$$DF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide $$^{188}$$Pb, following the $$beta$$ decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes.

論文

Detailed spectroscopy of doubly magic $$^{132}$$Sn

Benito, J.*; Fraile, L. M.*; Korgul, A.*; Piersa, M.*; Adamska, E.*; Andreyev, A. N.; $'A$lvarez-Rodr$'i$guez, R.*; 他81名*

Physical Review C, 102(1), p.014328_1 - 014328_18, 2020/07

The structure of the doubly magic $$^{132}_{50}$$Sn$$_{82}$$ has been investigated at the ISOLDE facility at CERN, populated both by the $$beta$$-decay of $$^{132}$$In and $$beta$$--delayed neutron emission of $$^{133}$$In. The level scheme of $$^{132}$$Sn is greatly expanded with the addition of 68 $$gamma$$-ray transitions and 17 levels. The identification of particle-hole multiplets both for protons and neutrons and the transition rates connecting different particle-hole configurations may provide input on the two-body matrix elements and single-particle states for state-of-the-art calculations.

論文

Spectrum of singly heavy baryons from a chiral effective theory of diquarks

Kim, Y.*; 肥山 詠美子*; 岡 眞; 鈴木 渓

Physical Review D, 102(1), p.014004_1 - 014004_9, 2020/07

 被引用回数:1 パーセンタイル:100(Astronomy & Astrophysics)

カイラル対称性に基づく有効理論を、現象論的なクォーク模型の閉じ込めポテンシャルと組み合わせることにより、ヘビークォークを1子含むバリオンの質量や構造の予言をおこなった。とりわけ、ダイクォーク質量の逆ヒエラルキー効果がチャームおよびボトムバリオンの質量準位に反映されることを予言した。

論文

Search for $$B^0$$ decays to invisible final states ($$+gamma$$) at Belle

Ku, Y.*; 谷田 聖; Belle Collaboration*; 他153名*

Physical Review D, 102(1), p.012003_1 - 012003_9, 2020/07

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

We report searches for $$B^0torm{invisible}$$ and $$B^0torm{invisible}+gamma$$ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a $$711,{rm fb}^{-1}$$ data sample that contains $$772 times 10^6 Bbar{B}$$ pairs and was collected near the $$Upsilon,(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. We observe no significant signal for either decay and set upper limits on their branching fractions at $$90%$$ confidence level of $$mathcal{B},(B^0torm{invisible}) < 7.8times10^{-5}$$ and $$mathcal{B},(B^0torm{invisible}+gamma) < 1.6times10^{-5}$$.

論文

Dalitz analysis of $$D^{0}to K^{-}pi^{+}eta$$ decays at Belle

Chen, Y. Q.*; 谷田 聖; Belle Collaboration*; 他181名*

Physical Review D, 102(1), p.012002_1 - 012002_12, 2020/07

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

We present the results of the first Dalitz plot analysis of the decay $$D^{0}to K^{-}pi^{+}eta$$. The analysis is performed on a data set corresponding to an integrated luminosity of 953 $$rm{fb}^{-1}$$ collected by the Belle detector at the asymmetric-energy $$e^{+}e^{-}$$ KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels $$bar{K}^{*}(892)^0eta$$, $$K^{-}a_0(980)^+$$, $$K^{-}a_2(1320)^+$$, $$bar{K}^{*}(1410)^0eta$$, $$K^{*}(1680)^-pi^{+}$$ and $$K_2^{*}(1980)^-pi^{+}$$, together with $$Kpi$$ and $$Keta$$ S-wave components. The decays $$K^{*}(1680)^{-}to K^{-}eta$$ and $$K_{2}^{*}(1980)^{-}to K^{-}eta$$ are observed for the first time. We measure ratio of the branching fractions, $$frac{mathcal{B}(D^{0}to K^{-}pi^{+}eta)}{mathcal{B}(D^{0}to K^{-}pi^{+})}=0.500 pm 0.002 {rm(stat)} pm0.020 {rm(syst)}pm 0.003 {rm (mathcal{B}_{PDG})}$$. Using the Dalitz fit result, the ratio $$frac{mathcal{B}(K^{*}(1680) to K eta)}{mathcal{B}(K^{*}(1680)to Kpi)}$$ is measured to be $$0.11 pm 0.02 {rm(stat)}^{+0.06}_{-0.04}{rm(syst)} pm 0.04{rm(mathcal{B}_{{PDG}})}$$; this is much lower than the theoretical expectations ($$approx 1$$) made under the assumption that $$K^{*}(1680)$$ is a pure $$1^{3}D_1$$ state. The product branching fraction $$mathcal{B}(D^0 to [K_2^{*}(1980)^- to K^{-} eta] pi^{+}) = (2.2^{+1.7}_{-1.9})times10^{-4}$$ is determined. In addition, the $$pieta^{prime}$$ contribution to the $$a_0(980)^{pm}$$ resonance shape is confirmed with 10.1$$sigma$$ statistical significance using the three-channel Flatte model. We also measure $$mathcal{B}(D^0tobar{K}^{*}(892)^0eta)=(1.41^{+0.13}_{-0.12})%$$. This is consistent with, and more precise than, the current world average $$(1.02pm0.30)%$$, deviates with a significance of more than $$3sigma$$ from the theoretical predictions of (0.51-0.92)%.

論文

First- and second-order topological superconductivity and temperature-driven topological phase transitions in the extended Hubbard model with spin-orbit coupling

Kheirkhah, M.*; Yan, Z.*; 永井 佑紀; Marsiglio, F.*

Physical Review Letters, 125(1), p.017001_1 - 017001_8, 2020/07

 被引用回数:0 パーセンタイル:100(Physics, Multidisciplinary)

近年、高次トポロジカル物質と言われる、今までにない新しいタイプのトポロジカル物質が注目を集めている。特に、超伝導体と半導体を接合させた場合、高次トポロジカル超伝導状態が現れると期待され、そしてトポロジカル量子コンピューティングが可能な新しいマヨラナ状態が出現するということで盛んに研究が行われている。本研究では、固体物理における基本的な模型である拡張ハバード模型にスピン軌道相互作用が存在するとき、温度とキャリアドープ量によって1次トポロジカル超伝導と2次トポロジカル超伝導および通常の超伝導の複数の相が現れることを明らかにした。本研究では、高次トポロジカル超伝導状態が容易に実現する方法を提案したことになる。

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