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論文

Intrinsic factors responsible for brittle versus ductile nature of refractory high-entropy alloys

都留 智仁; Han, S.*; 松浦 周太郎*; Chen, Z.*; 岸田 恭輔*; Lobzenko, I.; Rao, S.*; Woodward, C.*; George, E.*; 乾 晴行*

Nature Communications (Internet), 15, p.1706_1 - 1706_10, 2024/02

https://doi.org/10.1038/s41467-024-45639-8
 被引用回数：44 パーセンタイル：98.99(Multidisciplinary Sciences)

耐火ハイエントロピー合金(RHEA)は、超高温用途への応用の可能性から注目されている。しかし、体心立方結晶をもつため面心立方HEAよりも脆く、さらに、主要なNi基超合金やFCC合金系の材料よりも著しく低いクリープ強度を示す。これらの欠点を克服し、RHEAを実用的な構造材料に発展させるためには、強度と延性を制御する要因の基礎的な理解を深める必要がある。本研究では、TiZrHfNbTaとVNbMoTaWという2つのモデルRHEAを調査し、前者は77Kまで塑性圧縮可能であるのに対し、後者は298K以下では圧縮不可能であることを示した。TiZrHfNbTaの六方最密充填(HCP)元素は、すべての構成元素がBCCであるVNbMoTaWと比較して、転位芯エネルギーを下げ、格子歪みを大きくし、せん断弾性率を下げることで、高い延性と相対的に高い降伏強度につながることがわかった。転位芯構造はVNbTaMoWではコンパクトで、TiZrHfNbTaでは拡張しており、2つのRHEAで異なる滑り面が活性化していることがわかった。これらは、いずれもHCP元素の濃度に起因していることが第一原理計算により明らかになった。この結果は、HCP元素とBCC元素の比率に関連した電子構造の変化を利用して、強度、延性、すべり挙動を制御し、より効率的な発電所や輸送のための次世代高温材料を開発できることを実証している。

論文

Si-addition contributes to overcoming the strength-ductility trade-off in high-entropy alloys

Wei, D.*; Gong, W.; 都留 智仁; Lobzenko, I.; Li, X.*; Harjo, S.; 川崎 卓郎; Do, H.-S.*; Bae, J. W.*; Wagner, C.*; et al.

International Journal of Plasticity, 159, p.103443_1 - 103443_18, 2022/12

https://doi.org/10.1016/j.ijplas.2022.103443
 被引用回数：117 パーセンタイル：99.80(Engineering, Mechanical)

Face-centered cubic single-phase high-entropy alloys (HEAs) containing multi-principal transition metals have attracted significant attention, exhibiting an unprecedented combination of strength and ductility owing to their low stacking fault energy (SFE) and large misfit parameter that creates severe local lattice distortion. Increasing both strength and ductility further is challenging. In the present study, we demonstrate via meticulous experiments that the CoCrFeNi HEA with the addition of the substitutional metalloid Si can retain a single-phase FCC structure while its yield strength (up to 65%), ultimate strength (up to 34%), and ductility (up to 15%) are simultaneously increased, owing to a synthetical effect of the enhanced solid solution strengthening and a reduced SFE. The dislocation behaviors and plastic deformation mechanisms were tuned by the addition of Si, which improves the strain hardening and tensile ductility. The present study provides new strategies for enhancing HEA performance by targeted metalloid additions.

論文

Micro- to nano-scale areal heterogeneity in pore structure and mineral compositions of a sub-decimeter-sized Eagle Ford Shale

Wang, Q.*; Hu, Q.*; Zhao, C.*; Yang, X.*; Zhang, T.*; Ilavsky, J.*; Kuzmenko, I.*; Ma, B.*; 舘 幸男

International Journal of Coal Geology, 261, p.104093_1 - 104093_15, 2022/09

https://doi.org/10.1016/j.coal.2022.104093
 被引用回数：13 パーセンタイル：70.22(Energy & Fuels)

To understanding the spatial heterogeneity of mineral and pore structure variations in fine-grained shale, microscale X-ray fluorescence (micro-XRF) mapping, (ultra-) small-angle X-ray scattering [(U)SAXS] and wide-angle X-ray scattering were applied for two samples from a piece of Eagle Ford Shale in South Texas. Thin section petrography and field emission-scanning electron microscopy, X-ray diffraction (XRD), total organic carbon, and pyrolysis were also utilized to investigate the potential spatial heterogeneity of pore types, mineral and organic matter compositions for both samples. Overall, the siliceous-carbonate mineral contents in these carbonate-rich Eagle Ford Shale vary between laminations at mm scales. By analyzing six selected sub-samples on each of two samples with X-ray scattering and XRD techniques, nm-sized pores are mainly interparticle ones in the higher calcite regions, where the porosity is also relatively lower, while the lower calcite regions consist of both interparticle and intraparticle pore types with higher porosity. Finally, the micro-XRF and (U)SAXS are combined to generate porosity distribution maps to provide more insights about its heterogeneity related to the laminations and fractures at our observational scales.

論文

Phonon softening in Lu(Pt$$_{1-x}$$Pd$$_x$$)$$_2$$In close to a zero-temperature structural instability

Gruner, T.*; Lucas, S.*; Geibel, C.*; 金子 耕士; 筒井 智嗣*; Schmalzl, K.*; Stockert, O.*

Physical Review B, 106(11), p.115142_1 - 115142_6, 2022/09

https://doi.org/10.1103/PhysRevB.106.115142
 被引用回数：1 パーセンタイル：5.72(Materials Science, Multidisciplinary)

The disappearance of a charge-density-wave (CDW) transition in Lu(Pt$$_{1-x}$$Pd$$_x$$)$$_2$$In is thought to be closely linked to a maximum of the superconducting transition temperature in the system. We studied the superstructure and the phonon softening in Lu(Pt$$_{0.5}$$Pd$$_{0.5}$$)$$_2$$In by means of neutron and high-resolution inelastic X-ray scattering. A full phonon softening at $$q_{textrm{CDW}}$$ = (0.5, 0.5, 0) with the appearance of superstructure peaks could be clearly identified. The large tail of the superstructure intensity above the CDW transition indicates the importance of critical fluctuations.

論文

Axial U(1) symmetry at high temperatures in $$N_f=2+1$$ lattice QCD with chiral fermions

青木 慎也*; 青木 保道*; 深谷 英則*; 橋本 省二*; 金森 逸作*; 金児 隆志*; 中村 宜文*; Rohrhofer, C.*; 鈴木 渓

Proceedings of Science (Internet), 396, p.332_1 - 332_7, 2022/07

https://doi.org/10.22323/1.396.0332

高温QCDにおける軸性U(1)異常の振る舞いはQCDの相図を理解するために重要である。JLQCD Collaborationによる以前の研究では、ドメインウォール・フェルミオンや(再重み付け法によって得られる)オーバーラップ・フェルミオンのような動的なカイラルフェルミオンを用いて2フレーバーQCDの高温相のシミュレーションを行った。本研究では、このシミュレーションを2+1フレーバー動的クォークを含む系へと拡張する。ここで、アップ、ダウン、ストレンジクォークは物理点近傍の質量をとし、2+1フレーバーQCDの擬臨界温度近傍、あるいはやや高い温度でシミュレーションを行う。本講演では、このシミュレーションから得られたディラックスペクトル、トポロジカル感受率、軸性U(1)感受率、ハドロン相関関数の結果を報告する。

論文

Programmable synthesis of silver wheels

Kwon, H.*; Pietrasiak, E.*; 大原 高志; 中尾 朗子*; Chae, B.*; Hwang, C.-C.*; Jung, D.*; Hwang, I.-C.*; Ko, Y. H.*; Kim, K.*; et al.

Inorganic Chemistry, 60(9), p.6403 - 6409, 2021/05

https://doi.org/10.1021/acs.inorgchem.1c00106
 被引用回数：1 パーセンタイル：5.43(Chemistry, Inorganic & Nuclear)

The synthesis of sandwich-shaped multinuclear silver complexes with planar penta- and tetranuclear wheel-shaped silver units and a central anion is reported, along with complete spectroscopic and structural characterization. An NMR mechanistic study reveals that silver complexes were formed in the following order: 2Ag $$rightarrow$$ 3Ag$$^{rm H2O}$$ $$rightarrow$$ 5Ag$$^{rm OH}$$ $$rightarrow$$ 4Ag$$^{rm OH}$$. The central hydroxides in 4Ag$$^{rm OH}$$ and 5Ag$$^{rm OH}$$ exhibit exotic physical properties due to the confined environment inside the complex. The size of these silver wheels can be tuned by changing the central anion or extracting/adding one silver atom. This study provides the facile way to synthesize discrete wheel-shaped multinuclear silver complexes and provides valuable insights into the dynamics of the self-assembly process.

論文

Study of the axial $$U(1)$$ anomaly at high temperature with lattice chiral fermions

青木 慎也*; 青木 保道*; Cossu, G.*; 深谷 英則*; 橋本 省二*; 金児 隆志*; Rohrhofer, C.*; 鈴木 渓

Physical Review D, 103(7), p.074506_1 - 074506_18, 2021/04

https://doi.org/10.1103/PhysRevD.103.074506
 被引用回数：31 パーセンタイル：86.66(Astronomy & Astrophysics)

本研究では、格子QCDシミュレーションを用いて190-330MeVの温度領域における2フレーバーQCDの軸性$$U(1)$$アノマリーの性質を調べる。厳密なカイラル対称性を保つための格子フェルミオンとして、メビウス・ドメインウォール・フェルミオンや再重みづけ法によって構成されるオーバーラップ・フェルミオンを採用する。格子間隔は先行研究より小さい0.07fm程度であり、有限体積効果を正しく制御するために複数の体積でシミュレーションを行う。測定量として、トポロジカル感受率,軸性$$U(1)$$感受率,メソン/バリオン相関関数における$$U(1)$$パートナー間の縮退などの振る舞いを見る。臨界温度以上のすべての結果は、軸性$$U(1)$$対称性の破れが統計誤差の範囲でゼロと無矛盾であることを示唆している。クォーク質量依存性の結果は、$$SU(2)_L times SU(2)_R$$カイラル対称性の破れと同程度に軸性$$U(1)$$対称性が回復していることを示唆している。

論文

Development of a new microdosimetric biological weighting function for the RBE$$_{10}$$ assessment in case of the V79 cell line exposed to ions from $$^{1}$$H to $$^{238}$$U

Parisi, A.*; 佐藤 達彦; 松谷 悠佑; 加瀬 優紀*; Magrin, G.*; Verona, C.*; Tran, L.*; Rosenfeld, A.*; Bianchi, A.*; Olko, P.*; et al.

Physics in Medicine & Biology, 65(23), p.235010_1 - 235010_20, 2020/12

https://doi.org/10.1088/1361-6560/abbf96
 被引用回数：35 パーセンタイル：88.22(Engineering, Biomedical)

ミクロ線量分布からV79細胞の10%生存率をエンドポイントとした生物学的効果比(RBE)加重線量を推定する新たな生物学的加重関数を開発した。その開発には、$$^{1}$$Hから$$^{238}$$Uまでの様々なイオン照射に対するV79細胞生存率を格納したデータベースと、粒子・重イオン輸送計算コードPHITSのマイクロドジメトリ機能を用いて計算したミクロ線量分布が活用された。開発した生物学的加重関数の信頼性は、他のモデルによる計算結果や種々のイオンに関する実験データとの比較により検証した。本成果により、実験により評価したミクロ線量分布からRBE加重線量を誰でも容易に推定可能となり、粒子線治療場におけるマイクロドジメトリ測定の有用性が高まった。

論文

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; 上坂 友洋*; 川瀬 頌一郎; Beaumel, D.*; 堂園 昌伯*; 藤井 俊彦*; 福田 直樹*; 福永 拓*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

https://doi.org/10.1103/PhysRevLett.124.212502
 被引用回数：19 パーセンタイル：72.51(Physics, Multidisciplinary)

中性子過剰核$$^{25}$$Fの構造が($$p,2p$$)反応で調査した。$$pi 0d_{5/2}$$軌道の分光学的因子は1.0$$pm$$0.3と大きいが、一方で残留核である$$^{24}$$Oが基底状態である割合は約35%,励起状態は約0.65%であることが明らかになった。この結果は、$$^{25}$$Fのコア核$$^{24}$$Oは基底状態とは大きく異なり、$$^{24}$$Oの$$0d_{5/2}$$軌道に陽子がひとつ加わることで$$^{24}$$Oと$$^{25}$$Fの中性子軌道が相当に変化していると推測される。これは酸素同位体ドリップライン異常のメカニズムである可能性がある。

論文

${it In-situ}$ observation and analysis of solid-state diffusion and liquid migration in a crystal growth system; A Segregation-driven diffusion couple

Tremsin, A. S.*; Perrodin, D.*; Losko, A. S.*; Vogel, S. C.*; 篠原 武尚; 及川 健一; Bizarri, G. A.*; Bourret, E. D.*; Peterson, J. H.*; Wang, K. P.*; et al.

Acta Materialia, 186, p.434 - 442, 2020/03

https://doi.org/10.1016/j.actamat.2020.01.013
 被引用回数：8 パーセンタイル：33.58(Materials Science, Multidisciplinary)

Energy-resolved neutron imaging is employed for ${it in situ}$ measurements of dopant transport in a simple experiment performed before the crystal growth of the scintillator BaBrCl:5%Eu via a vertical gradient freeze technique. During a stabilization period preceding growth, we observed the diffusion of Eu from the solid phase into the melt over a period of approximately 4 h. Comparing the measured centerline concentration profile with a mathematical model for the system, we estimate the solid-state diffusivity of Eu in BaBrCl as $$D$$$$_{1}$$ = 1.9 $$times$$ 10$$^{-10}$$ m$$^{2}$$/s and an upper limit for the liquid-phase diffusivity of Eu in the melt as $$D$$$$_2^{*}$$ = 2.5 $$times$$ 10$$^{-10}$$ m$$^{2}$$/s, at temperatures near the melting point. We compare this experiment, where diffusion is driven by a concentration discontinuity arising from segregation, to the classical diffusion couple technique.

論文

Nuclear-modification factor of charged hadrons at forward and backward rapidity in $$p+$$Al and $$p+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他297名*

Physical Review C, 101(3), p.034910_1 - 034910_16, 2020/03

https://doi.org/10.1103/PhysRevC.101.034910
 被引用回数：21 パーセンタイル：86.24(Physics, Nuclear)

The PHENIX experiment has studied nuclear effects in $$p$$$$+$$Al and $$p$$$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV on charged hadron production at forward rapidity ($$1.4< eta < 2.4$$, $$p$$-going direction) and backward rapidity ($$-2.2 < eta < -1.2$$, $$A$$-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central $$p$$$$+$$Al and $$p$$$$+$$Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in $$p$$+$$p$$ collisions. The magnitude of enhancement at backward rapidity is larger in $$p$$$$+$$Au collisions than in $$p$$$$+$$Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.

論文

Nuclear dependence of the transverse single-spin asymmetry in the production of charged hadrons at forward rapidity in polarized $$p+p$$, $$p+$$Al, and $$p+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他296名*

Physical Review Letters, 123(12), p.122001_1 - 122001_9, 2019/09

https://doi.org/10.1103/PhysRevLett.123.122001
 被引用回数：13 パーセンタイル：62.58(Physics, Multidisciplinary)

We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively-charged hadrons in polarized $$p^{uparrow}+p$$, $$p^{uparrow}+$$Al and $$p^{uparrow}+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. The measurements have been performed at forward rapidity ($$1.4 < eta < 2.4$$) over the range of $$1.8 < p_{T} < 7.0$$ GeV$$/c$$ and $$0.1 < x_{F} < 0.2$$. We observed a positive asymmetry $$A_{N}$$ for positively-charged hadrons in $$p^{uparrow}+p$$ collisions, and a significantly reduced asymmetry in $$p^{uparrow}$$+$$A$$ collisions. These results reveal a nuclear dependence of charged hadron $$A_N$$ in a regime where perturbative techniques are relevant. These results provide new opportunities to use $$p^{uparrow}+$$A collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSA as a new handle in studying small-system collisions.

論文

Measurement of charm and bottom production from semileptonic hadron decays in $$p+p$$ collisions at $$sqrt{s}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他296名*

Physical Review D, 99(9), p.092003_1 - 092003_21, 2019/05

AA2019-0568.pdf:2.19MB

https://doi.org/10.1103/PhysRevD.99.092003
 被引用回数：7 パーセンタイル：33.59(Astronomy & Astrophysics)

Measurements of the differential production of electrons from open-heavy-flavor hadrons with charm- and bottom-quark content in $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=200$$ GeV are presented. The measurements proceed through displaced-vertex analyses of electron tracks from the semileptonic decay of charm and bottom hadrons using the PHENIX silicon-vertex detector. The relative contribution of electrons from bottom decays to inclusive heavy-flavor-electron production is found to be consistent with fixed-order-plus-next-to-leading-log perturbative-QCD calculations within experimental and theoretical uncertainties. These new measurements in $$p$$$$+$$$$p$$ collisions provide a precision baseline for comparable forthcoming measurements in A$$+$$A collisions.

論文

Nonperturbative-transverse-momentum broadening in dihadron angular correlations in $$sqrt{s_{NN}}=200$$ GeV proton-nucleus collisions

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他293名*

Physical Review C, 99(4), p.044912_1 - 044912_10, 2019/04

AA2019-0570.pdf:0.56MB

https://doi.org/10.1103/PhysRevC.99.044912
 被引用回数：6 パーセンタイル：45.26(Physics, Nuclear)

The PHENIX collaboration has measured high-$$p_T$$ dihadron correlations in $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. The correlations arise from inter- and intra-jet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of $$p_{rm out}$$, the transverse momentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initial and final state transverse momenta. These distributions are measured multi-differentially as a function of $$x_E$$, the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The near-side $$p_{rm out}$$ widths, sensitive to fragmentation transverse momentum, show no significant broadening between $$p$$$$+$$Au, $$p$$$$+$$Al, and $$p$$$$+$$$$p$$. The away-side nonperturbative $$p_{rm out}$$ widths are found to be broadened in $$p$$$$+$$Au when compared to $$p$$$$+$$$$p$$; however, there is no significant broadening in $$p$$$$+$$Al compared to $$p$$$$+$$$$p$$ collisions. The data also suggest that the away-side $$p_{rm out}$$ broadening is a function of $$N_{rm coll}$$, the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to initial and final state transverse momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.

論文

Measurements of $$mumu$$ pairs from open heavy flavor and Drell-Yan in $$p+p$$ collisions at $$sqrt{s}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他287名*

Physical Review D, 99(7), p.072003_1 - 072003_41, 2019/04

AA2019-0566.pdf:3.21MB

https://doi.org/10.1103/PhysRevD.99.072003
 被引用回数：24 パーセンタイル：71.50(Astronomy & Astrophysics)

PHENIX reports differential cross sections of $$mumu$$ pairs from semileptonic heavy-flavor decays and the Drell-Yan production mechanism measured in $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=200$$ GeV at forward and backward rapidity ($$1.2 < |eta| < 2.2$$). The $$mumu$$ pairs from $$cbar{c}$$, $$bbar{b}$$, and Drell-Yan are separated using a simultaneous fit to unlike- and like-sign muon pair spectra in mass and $$p_T$$. The azimuthal opening angle correlation between the muons from $$cbar{c}$$ and $$bbar{b}$$ decays and the pair-$$p_T$$ distributions are compared to distributions generated using ${sc pythia}$ and ${sc powheg}$ models, which both include next-to-leading order processes. The measured distributions for pairs from $$cbar{c}$$ are consistent with ${sc pythia}$ calculations. The $$cbar{c}$$ data presents narrower azimuthal correlations and softer $$p_T$$ distributions compared to distributions generated from ${sc powheg}$. The $$bbar{b}$$ data are well described by both models. The extrapolated total cross section for bottom production is $$3.75{pm}0.24({rm stat}){pm}^{0.35}_{0.50}({rm syst}){pm}0.45({rm global})$$[$$mu$$b], which is consistent with previous measurements at the Relativistic Heavy Ion Collider in the same system at the same collision energy, and is approximately a factor of two higher than the central value calculated with theoretical models. The measured Drell-Yan cross section is in good agreement with next-to-leading-order quantum-chromodynamics calculations.

論文

Creation of quark-gluon plasma droplets with three distinct geometries

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他312名*

Nature Physics, 15(3), p.214 - 220, 2019/03

https://doi.org/10.1038/s41567-018-0360-0
 被引用回数：123 パーセンタイル：98.31(Physics, Multidisciplinary)

Experimental studies of the collisions of heavy nuclei at relativistic energies have established the properties of the quark-gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons. In this state, matter behaves as a nearly inviscid fluid that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the particles produced, creating a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton-proton and proton-nucleus (p+A) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP. Here we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton-gold (p+Au), deuteron-gold (d+Au) and helium-gold ($$^{3}$$He+Au) collisions at a nucleon-nucleon centre-of-mass energy $$sqrt{s_{{mathrm{NN}}}}$$ = 200 GeV. The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide the best simultaneous description of these measurements.

論文

Production of $$pi^0$$ and $$eta$$ mesons in Cu+Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV

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397名*

Physical Review C, 98(5), p.054903_1 - 054903_11, 2018/11

https://doi.org/10.1103/PhysRevC.98.054903
 被引用回数：14 パーセンタイル：69.50(Physics, Nuclear)

Production of $$pi^0$$ and $$eta$$ mesons has been measured at midrapidity in Cu$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV. Measurements were performed in $$pi^0(eta)rightarrowgammagamma$$ decay channel in the 1(2)-20 GeV/$$c$$ transverse momentum range. A strong suppression is observed for $$pi^0$$ and $$eta$$ meson production at high transverse momentum in central Cu$$+$$Au collisions relative to the $$p$$$$+$$$$p$$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au$$+$$Au with comparable nuclear overlap. The $$eta/pi^0$$ ratio measured as a function of transverse momentum is consistent with $$m_T$$-scaling parameterization down to $$p_T=$$2 GeV/$$c$$, its asymptotic value is constant and consistent with Au$$+$$Au and $$p$$$$+$$$$p$$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $$e^+e^-$$ collisions in a range of collision energies $$sqrt{s_{_{NN}}}=$$ 3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu$$+$$Cu collisions either does not affect the jet fragmentation into light mesons or it affects the $$pi^0$$ and $$eta$$ the same way.

論文

Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in $$p+p$$ collisions at $$sqrt{s}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他287名*

Physical Review D, 98(7), p.072004_1 - 072004_13, 2018/10

AA2018-0655.pdf:1.13MB

https://doi.org/10.1103/PhysRevD.98.072004
 被引用回数：2 パーセンタイル：10.94(Astronomy & Astrophysics)

Dihadron and isolated direct photon-hadron angular correlations are measured in $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=200$$ GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum $$k_T$$ and $$j_T$$ in the azimuthal nearly back-to-back region $$Deltaphisimpi$$. In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of $$p_{rm out}$$, the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at $$sqrt{s}=510$$ GeV. The nonperturbative jet widths also appear to increase with $$sqrt{s}$$ at a similar $$x_T$$, which is qualitatively consistent to similar measurements in Drell-Yan interactions.

論文

Single-spin asymmetry of $$J/psi$$ production in $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collisions with transversely polarized proton beams at $$sqrt{s_{_{NN}}}=200$$ GeV

Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他286名*

Physical Review D, 98(1), p.012006_1 - 012006_11, 2018/07

AA2018-0590.pdf:0.75MB

https://doi.org/10.1103/PhysRevD.98.012006
 被引用回数：13 パーセンタイル：50.18(Astronomy & Astrophysics)

We report the transverse single-spin asymmetries of $$J/psi$$ production at forward and backward rapidity, $$1.2<|y|<2.2$$, as a function of $$J/psi$$ transverse momentum ($$p_T$$) and Feynman-$$x$$ ($$x_F$$). The data analyzed were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from $$p$$$$+$$$$p$$, $$p$$$$+$$Al, and $$p$$$$+$$Au collisions with transversely polarized proton beams at $$sqrt{s_{_{NN}}}=200$$ GeV. At this collision energy, single-spin asymmetries for heavy-flavor particle production of $$p$$$$+$$$$p$$ collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton + nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate negative asymmetries at the two-standard-deviation level in the $$p$$$$+$$Au data for $$p_T<2$$ GeV/$$c$$ at both forward and backward rapidity, while in $$p$$$$+$$$$p$$ and $$p$$$$+$$Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.

論文

Retreat from stress; Rattling in a planar coordination

末國 晃一郎*; Lee, C. H.*; 田中 博己*; 西堀 英治*; 中村 篤*; 笠井 秀隆*; 森 仁志*; 臼井 秀知*; 越智 正之*; 長谷川 巧*; et al.

Advanced Materials, 30(13), p.1706230_1 - 1706230_6, 2018/03

https://doi.org/10.1002/adma.201706230
 被引用回数：64 パーセンタイル：89.32(Chemistry, Multidisciplinary)

高性能デバイスとしての熱電材料には、高い電気伝導度と低い熱伝導度という相反する要求を同時に満たす必要がある。本研究では、テトラへドライト(Cu,Zn)$$_{12}$$(Sb,As)$$_{4}$$S$$_{13}$$の結晶構造とフォノンダイナミクスを調べ、平面内に配位している銅原子のラットリング運動がフォノンを効率良く散乱することを見出した。これらの知見は、平面配位構造を有する高性能熱電材料の新たな開発指針を与えるものである。

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