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Downward terrestrial gamma-ray flash observed in a winter thunderstorm

和田 有希*; 榎戸 輝揚*; 中澤 知洋*; 古田 禄大; 湯浅 孝行*; 中村 佳敬*; 森本 健志*; 松元 崇弘*; 牧島 一夫*; 土屋 晴文

Physical Review Letters, 123(6), p.061103_1 - 061103_6, 2019/08

During a winter thunderstorm on 2017 November 24, a strong burst of gamma-rays with energies up to $$sim$$10 MeV was detected coincident with a lightning discharge, by scintillation detectors installed at Kashiwazaki-Kariwa Nuclear Power Plant at sea level in Japan. The burst had a sub-second duration, which is suggestive of photoneutron productions. The leading part of the burst was resolved into four intense gamma-ray bunches, each coincident with a low-frequency radio pulse. These bunches were separated by 0.7$$-$$1.5 ms, with a duration of $$<$$1 ms each. Thus, the present burst may be considered as a "downward" terrestrial gamma-ray flash (TGF), which is analogous to up-going TGFs observed from space. Although the scintillation detectors were heavily saturated by these bunches, the total dose associated with them was successfully measured by ionization chambers, employed by nine monitoring posts surrounding the power plant. From this information and Monte Carlo simulations, the present downward TGF is suggested to have taken place at an altitude of 2500$$pm$$500 m, involving $$8^{+8}_{-4} times10^{18}$$ avalanche electrons with energies above 1 MeV which is comparable to those in up-going TGFs.



榎戸 輝揚*; 和田 有希*; 土屋 晴文

日本物理学会誌, 74(4), p.192 - 200, 2019/04



"$$K^-pp$$", a $$bar K$$-meson nuclear bound state, observed in $$^3$$He($$K^-,Lambda p)n$$ reactions

橋本 直; 谷田 聖; 他67名*

Physics Letters B, 789, p.620 - 625, 2019/02

 パーセンタイル:100(Astronomy & Astrophysics)

$$^{3}{rm He}(K^-, , Lambda p)n$$における$$Lambda p$$不変質量分布において$$m_K + 2m_p$$、つまり$$K^-$$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。$$q$$ = 350$$sim$$650MeV/$$c$$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($$overline{K}N rightarrow overline{K}N$$)に続いて残りの2各紙に吸収される反応($$overline{K}NN rightarrow Lambda N$$)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$$B_{rm {it Kpp}} = 47 pm 3 , (stat.) ,^{+3}_{-6},(sys.)$$ MeV、幅$$Gamma_{rm {it Kpp}} = 115 pm 7 , (stat.),^{+10}_{-20} ,(sys.)$$ MeV、そして$$S$$波ガウス形状因子パラメータ$$Q_{rm {it Kpp}} = 381 pm 14 , (stat.),^{+57}_{-0} ,(sys.)$$MeV/$$c$$という値が"$$K^-pp$$"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。


Extraction behavior of rutherfordium as a cationic fluoride complex with a TTA chelate extractant from HF/HNO $$_{3}$$ acidic solutions

横山 明彦*; 北山 雄太*; 福田 芳樹*; 菊永 英寿*; 村上 昌史*; 小森 有希子*; 矢納 慎也*; 羽場 宏光*; 塚田 和明; 豊嶋 厚史*

Radiochimica Acta, 107(1), p.27 - 32, 2019/01

 パーセンタイル:100(Chemistry, Inorganic & Nuclear)

The aim of this study was to identify relevant Rf chemical species by using reversed-phase extraction chromatography with 2-thenoyltrifluoroacetone (TTA) resin as the stationary phase. Because TTA can be used to extract specific metal ions, the distribution ratios of the system enabled determination of the specific complex formation constant of Rf. We performed several experiments on chemical systems with Zr, Hf, No, and Rf, determined their adsorption coefficients, and deduced the K values for Rf.


Radiative transitions of doubly charmed baryons in lattice QCD

Bartiyar, H.*; Can, K. U.*; Erkol, G.*; 岡 眞; 高橋 徹*

Physical Review D, 98(11), p.114505_1 - 114505_14, 2018/12

 被引用回数:2 パーセンタイル:64.74(Astronomy & Astrophysics)



Phase-transition kinetics of magnetic skyrmions investigated by stroboscopic small-angle neutron scattering

中島 多朗*; 稲村 泰弘; 伊藤 崇芳*; 大石 一城*; 大池 広志*; 賀川 史敬*; 吉川 明子*; 田口 康二郎*; 加倉井 和久*; 十倉 好紀*; et al.

Physical Review B, 98(1), p.014424_1 - 014424_5, 2018/07

 被引用回数:1 パーセンタイル:59.26(Materials Science, Multidisciplinary)



Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

和田 有希*; Bowers, G. S.*; 榎戸 輝揚*; 鴨川 仁*; 中村 佳敬*; 森本 健志*; Smith, D.*; 古田 禄大*; 中澤 知洋*; 湯浅 孝行*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

 被引用回数:1 パーセンタイル:53.8(Geosciences, Multidisciplinary)

An on-ground observation program for high energy atmospheric phenomena in winter thunderstorms along Japan Sea has been performed via lightning measurements of $$gamma$$-ray radiation, atmospheric electric field and low-frequency radio band. On February 11, 2017, the radiation detectors recorded $$gamma$$-ray emission lasting for 75 sec. The $$gamma$$-ray spectrum extended up to 20 MeV and was reproduced by a cutoff power-law model with a photon index of 1.36$$^{+0.03}_{-0.04}$$, being consistent with a Bremsstrahlung radiation from a thundercloud (as known as a $$gamma$$-ray glow). Then the $$gamma$$-ray glow was abruptly terminated with a nearby lightning discharge. The low-frequency radio monitors, installed $$sim$$50 km away from Noto School, recorded intra/inter-cloud discharges spreading over $$sim$$60km area with a $$sim$$300 ms duration. The timing of the $$gamma$$-ray termination coincided with the moment when a sequence of intra/inter-cloud discharges passed 0.7 km horizontally away from the radiation monitors. The atmospheric electric-field measurement presented that negative charge was located in the cloud base and not neutralized by the lightning discharge. This indicates that the $$gamma$$-ray source was located at an higher region than the cloud base.



池田 義雅*; 高村 正人*; 箱山 智之*; 大竹 淑恵*; 熊谷 正芳*; 鈴木 裕士

鉄と鋼, 104(3), p.138 - 144, 2018/03

 パーセンタイル:100(Metallurgy & Metallurgical Engineering)



Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

田中 泰貴*; 成清 義博*; 森田 浩介*; 藤田 訓裕*; 加治 大哉*; 森本 幸司*; 山木 さやか*; 若林 泰生*; 田中 謙伍*; 武山 美麗*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 被引用回数:3 パーセンタイル:29.91(Physics, Multidisciplinary)

ガス充填型反跳生成核分離装置GARISを用いて$$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, $$^{48}$$Ca + $$^{248}$$Cm反応系における準弾性散乱断面積の励起関数を測定した。これらのデータから融合障壁分布を導出し、チャンネル結合計算と比較した。$$^{48}$$Ca + $$^{208}$$Pb及び$$^{50}$$Ti + $$^{208}$$Pb反応の障壁分布のピークエネルギーはそれらの反応系における2中性子蒸発断面積のピークエネルギーと良く一致し、一方$$^{48}$$Ca + $$^{248}$$Cm反応の障壁分布のピークエネルギーは4中性子蒸発断面積のピークエネルギーより少し下に現れることが判った。この結果は超重核合成の際の最適ビームエネルギーの予測に役立つ情報を与える。


Photonuclear reactions triggered by lightning discharge

榎戸 輝揚*; 和田 有希*; 古田 禄大*; 中澤 知洋*; 湯浅 孝行*; 奥田 和史*; 牧島 一夫*; 佐藤 光輝*; 佐藤 陽祐*; 中野 俊男*; et al.

Nature, 551(7681), p.481 - 484, 2017/11

 被引用回数:26 パーセンタイル:3.91(Multidisciplinary Sciences)

Relativistic electrons accelerated by electric fields of lightnings and thunderclouds emit bremsstrahlung $$gamma$$ rays, which have been detected at ground observations. The energy of the $$gamma$$ rays is sufficiently high to potentially invoke atmospheric photonuclear reactions $$^{14}$$N($$gamma$$, n)$$^{13}$$N, which would produce neutrons and eventually positrons via $$beta^{+}$$ decay of generated unstable radioactive isotopes, especially $$^{13}$$N. However, no clear observational evidence for the reaction has been reported to date. Here we report the first detection of neutron and positron signals from lightning with a ground observation. During a thunderstorm on 6 February 2017 in Japan, an intense $$gamma$$-ray flash ($$<$$1 ms) was detected at our monitoring sites. The subsequent initial burst quickly subsided with an exponential decay constant of 40-60 ms, followed by a prolonged line emission at $$sim$$0.511MeV, lasting for a minute. The observed decay timescale and spectral cutoff at $$sim$$10 MeV of the initial emission are well explained with de-excitation $$gamma$$ rays from the nuclei excited by neutron capture. The centre energy of the prolonged line emission corresponds to the electron-positron annihilation, and hence is the conclusive indication of positrons produced after the lightning. Our detection of neutrons and positrons is unequivocal evidence that natural lightning triggers photonuclear reactions.


$$Xi_c gamma rightarrowXi^prime_c$$ transition in lattice QCD

Bahtlyar, H.*; Can, K. U.*; Erkol, G.*; 岡 眞; 高橋 徹*

Physics Letters B, 772, p.121 - 126, 2017/09

 被引用回数:8 パーセンタイル:11.96(Astronomy & Astrophysics)

$$Xi_c gamma rightarrowXi_c^prime$$電磁遷移の形状因子を格子QCDを用いて計算した。


Study of the reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ at RIKEN-GARIS

加治 大哉*; 森田 浩介*; 森本 幸司*; 羽場 宏光*; 浅井 雅人; 藤田 訓裕*; Gan, Z.*; Geissel, H.*; 長谷部 裕雄*; Hofmann, S.*; et al.

Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03

 被引用回数:10 パーセンタイル:12.59(Physics, Multidisciplinary)

理化学研究所のガス充填型反跳核分離装置GARISを用いて$$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$融合反応を調べた。116番元素$$^{292}$$Lv, $$^{293}$$Lvと思われる核反応生成物に起因するアルファ線と自発核分裂の崩壊連鎖が7事象観測された。崩壊連鎖中に観測された原子核の性質は過去の報告値とよく一致したが、1つの崩壊連鎖で一部矛盾が観測された。これは$$^{285}$$Cnの新しい自発核分裂分岐比の存在、あるいは新同位体$$^{294}$$Lv生成の可能性を示唆するものと思われる。


Complex chemistry with complex compounds

Eichler, R.*; 浅井 雅人; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D$"u$llmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.

EPJ Web of Conferences (Internet), 131, p.07005_1 - 07005_7, 2016/12


近年、物理的な前段分離装置を活用することにより、超重元素の比較的不安定な単一分子の合成と研究が気相化学研究によって可能になった。非常に揮発性の高い106番元素のヘキサカルボニル錯体Sg(CO)$$_{6}$$の合成は最近の大きな成果である。この成功を受けて、中心金属原子と周囲の配位子間の第一乖離エネルギーの測定を第2世代の実験として実施した。管状の分解反応装置を用いた手法を開発し、短寿命のMo(CO)$$_{6}$$, W(CO)$$_{6}$$, Sg(CO)$$_{6}$$錯体に適用することに成功した。


Enhanced sampling simulations to construct free-energy landscape of protein-partner substrate interaction

池部 仁善; 梅澤 公二*; 肥後 順一*

Biophysical Reviews, 8(1), p.45 - 62, 2016/03

Molecular dynamics (MD) simulations with both of all-atom and explicit solvent models provide the detailed behavior of protein-partner substrate binding at the atomic level. As the power of computational resources rise, MD simulations are being used more widely and easily. However it is still difficult to investigate thermodynamic properties of protein-partner substrate binding as well as protein folding with conventional MD simulations. Enhanced sampling methods have been developed to sample conformations reflecting equilibrium conditions in a more efficient manner than conventional MD simulations allowing the construction of accurate free energy landscapes. In this review, we discuss these enhanced sampling methods using a series of case by case examples. In particular we review enhanced sampling methods conforming to trivial trajectory parallelization (TTP), virtual-system coupled McMD (V-McMD), and adaptive lambda square dynamics (ALSD). These methods have been recently developed based on the existing method of multicanonical MD (McMD) simulation. Their applications are reviewed with an emphasis on describing their practical implementation. In our concluding remarks we explore extensions of the enhanced sampling methods that may allow for even more efficient sampling.


Simultaneous measurements of superradiance at multiple wavelength from helium excited states, 2; Analysis

大饗 千彰*; Harries, J.; 岩山 洋士*; 川口 健太郎*; 久間 晋*; 宮本 祐樹*; 永園 充*; 中嶋 享*; 中野 逸夫*; 繁政 英治*; et al.

Journal of the Physical Society of Japan, 85(3), p.034301_1 - 034301_10, 2016/03

 被引用回数:5 パーセンタイル:38.58(Physics, Multidisciplinary)

Previous experimental studies of superradiance (SR) in multi-level systems have been explainable using the predictions of the well-known simple two-level SR model. However our recent study using EUV free-electron laser excitation of helium atoms, where SR was observed at wavelengths of 502 nm, 668 nm, and 728 nm, revealed behaviour which necessitates a full multi-level treatment of the SR development. In this paper, we report simulations of the initial excitation by the FEL pulses, and the subsequent development of multi-level SR. The results of the simulation reproduce the experimental findings, and reveal that competitive SR on two transitions with a common upper level plays an important role in the development of the system.


H3 histone tail conformation within the nucleosome and the impact of K14 acetylation studied using enhanced sampling simulation

池部 仁善; 桜庭 俊*; 河野 秀俊

PLOS Computational Biology, 12(3), p.e1004788_1 - e1004788_13, 2016/03

 被引用回数:14 パーセンタイル:8.43(Biochemical Research Methods)

Acetylation of lysine residues in histone tails is associated with gene transcription. Because histone tails are structurally flexible and intrinsically disordered, it is difficult to experimentally determine the tail conformations and the impact of acetylation. In this work, we performed simulations to sample H3 tail conformations with and without acetylation. The results show that irrespective of the presence or absence of the acetylation, the H3 tail remains in contact with the DNA and assumes an alpha-helix structure in some regions. Acetylation slightly weakened the interaction between the tail and DNA and enhanced alpha-helix formation, resulting in a more compact tail conformation. We inferred that this compaction induces unwrapping and exposure of the linker DNA, enabling DNA-binding proteins (e.g., transcription factors) to bind to their target sequences. In addition, our simulation also showed that acetylated lysine was more often exposed to the solvent, which is consistent with the fact that acetylation functions as a post-translational modification recognition site marker.


Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(CO)$$_6$$ and W(CO)$$_6$$

Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; 羽場 宏光*; 浅井 雅人; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; et al.

Radiochimica Acta, 104(3), p.141 - 151, 2016/03

 被引用回数:8 パーセンタイル:10.94(Chemistry, Inorganic & Nuclear)



First $$alpha$$-$$gamma$$ spectroscopy using Si-Ge detector array installed at focal plane of GARIS

加治 大哉*; 森本 幸司*; 若林 泰生*; 武山 美麗*; 浅井 雅人

JPS Conference Proceedings (Internet), 6, p.030106_1 - 030106_4, 2015/06

超重核の$$alpha$$-$$gamma$$(X線)核分光実験を行うため、ガス充填型反跳イオン分離装置GARISの焦点面に新たにSi-Ge検出器アレイを導入した。このアレイの性能を$$^{207}$$Pb($$^{48}$$Ca,2n)$$^{253}$$No反応および$$^{208}$$Pb($$^{48}$$Ca,xn)$$^{256-x}$$No [x=1,2,3]反応を用いて試験した。$$alpha$$線との同時計数測定により$$^{253}$$Noと$$^{255}$$Noの$$alpha$$崩壊に伴う$$gamma$$線を明瞭に観測することに成功した。


Performance of new gas-filled recoil ion separator GARIS-II for asymmetric fusion reaction

加治 大哉*; 森本 幸司*; 若林 泰生*; 武山 美麗*; 山木 さやか*; 田中 謙伍*; 羽場 宏光*; Huang, M.*; 村上 昌史*; 金谷 淳平*; et al.

JPS Conference Proceedings (Internet), 6, p.030107_1 - 030107_4, 2015/06



A Streak camera study of superfluorescence at multiple wavelengths from helium atoms excited using free electron laser pulses

Harries, J.; 岩山 洋士*; 永園 充*; 富樫 格*; 矢橋 牧名*; 久間 晋*; 中嶋 享*; 宮本 祐樹*; 大饗 千彰*; 笹尾 登*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 48(10), p.105002_1 - 105002_9, 2015/05

 被引用回数:6 パーセンタイル:46.37(Optics)

We report the observation of superfluorescence at wavelengths (in air) of 501.6 nm, 667.8 nm, and 728.1 nm following the excitation of helium atoms with free-electron laser pulses at wavelengths of 53.7 nm ($$n$$=3 excitation) and 52.2 nm ($$n$$=4 excitation). The observed wavelengths of the superfluorescence pulses correspond to 1s3p-1s2s, 1s3d-1s2p, and 1s3s-2p transitions. Observation of superfluorescence on these transitions implies either competing cascade decays, or direct excitation of non-dipole allowed transitions. We have studied the time structure of the emitted pulses using a streak camera, and the results cannot be explained by straightforward considerations using the usual model for two-level superfluorescence.

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