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岩元 大樹; 新倉 潤*; 水野 るり恵*
Physical Review C, 111(3), p.034614_1 - 034614_13, 2025/03
被引用回数:0 パーセンタイル:0.00(Physics, Nuclear)1軌道上の負ミューオンは原子核に捕獲され、原子核崩壊過程を引き起こす。負ミューオンの全核捕獲率は、地球化学、宇宙核物理学、半導体デバイス開発などの分野できわめて重要であるが、現在の物理理論モデルによる正確な予測は依然として困難である。本研究では、ベイズ統計の枠組みで物理理論の情報と実験データを統合し、負ミューオンの全核捕獲率を推定する包括的な機械学習(ML)モデルを開発することを目的とした。本研究では、ガウス過程回帰に基づくMLモデルを採用し、不確かさが評価された実験データを学習データとして用いた。このモデルは事前情報としてGoulard-Primakoffの式を取り入れ、特にデータが乏しい領域での推定を可能にするために、転移学習の方法を適用した。開発したMLモデルは、精度と包括性の両方において物理理論モデルを上回ることが示され、モデル性能をさらに向上させるための重要な実験が特定された。本研究で生成された推定値は、ミューオン核データに組み込まれ、様々な研究分野に応用される予定である。
水野 るり恵*; 新倉 潤*; 齋藤 岳志*; 松崎 禎市郎*; 櫻井 博儀*; Amato, A.*; 浅利 駿介*; Biswas, S.*; Chiu, I.-H.; Gianluca, J.*; et al.
Nuclear Instruments and Methods in Physics Research A, 1060, p.169029_1 - 169029_14, 2024/03
被引用回数:2 パーセンタイル:46.61(Instruments & Instrumentation)We have developed a photon detection system for muonic X-ray spectroscopy. The detector system consists of high-purity germanium detectors with BGO Compton suppressors. The signals from the detectors are readout with a digital acquisition system. The absolute energy accuracy, energy and timing resolutions, photo-peak efficiency, the performance of the Compton suppressor, and high count rate durability are studied with standard -ray sources and in-beam experiment using
Al(
)
Si resonance reaction. The detection system was demonstrated at Paul Scherrer Institute. A calibration method for a photon detector at a muon facility using muonic X-rays of
Au and
Bi is proposed.
Pedersen, L. G.*; Sahin, E.*; Grgen, A.*; Bello Garrote, F. L.*; 角田 佑介*; 大塚 孝治*; 新倉 潤*; Orlandi, R.; 他59名*
Physical Review C, 107(4), p.044301_1 - 044301_10, 2023/04
被引用回数:3 パーセンタイル:45.98(Physics, Nuclear)Nuclei in the vicinity of Ni (
=28,
=50) are important benchmarks to study the evolution of shell structure far from stability. Excited states in
Cu were observed for the first time following the
-decay of
Ni, which was produced by in-flight fission of
U. Using
-ray coincidences, a level scheme comprising eight excited states was built. Using the observed
feeding and the
-decay properties of the excited states, spin was tentatively assigned to 5 new states. In addition to the
-decaying states, an isomeric state with a lifetime of 3.8(4) ms was found to decay by internal conversion. By comparing the results with large scale shell model calculations, quantitative information about the proton-neutron interaction outside the doubly magic
Ni core was obtained.
郷 慎太郎*; 井手口 栄治*; 横山 輪*; 青井 考*; Azaiez, F.*; 古高 和禎; 初川 雄一; 木村 敦; 木佐森 慶一*; 小林 幹*; et al.
Physical Review C, 103(3), p.034327_1 - 034327_8, 2021/03
被引用回数:4 パーセンタイル:44.13(Physics, Nuclear)Excited states in S were investigated by in-beam
-ray spectroscopy using the
Mg(
O, 2
1
) fusion-evaporation reaction. The de-exciting
-rays were measured with germanium detector arrays along with the measurement of evaporated charged particles in a
segmented Si detector array. The level scheme was extended up to 12470 keV. The obtained level structure is compared with the large-scale shell-model calculations. The possibility of isoscalar-pair excited states is discussed for
states with comparison between the experimental and theoretical results.
Sun, X. H.*; Wang, H.*; 大津 秀暁*; 櫻井 博儀*; Ahn, D. S.*; 合川 正幸*; 福田 直樹*; 磯部 忠昭*; 川上 駿介*; 小山 俊平*; et al.
Physical Review C, 101(6), p.064623_1 - 064623_12, 2020/06
被引用回数:7 パーセンタイル:55.65(Physics, Nuclear)理化学研究所RIビームファクトリーにて逆運動学法を使用し、核子当たり168MeVの陽子, 重陽子, 炭素イオン入射によるXeのスポレーションおよびフラグメンテーション反応からの同位体生成断面積を測定した。炭素イオンの場合は全運動エネルギーが高くなるため、質量数の小さな同位体の生成断面積が大きくなった。また、今回新たに測定されたデータを以前により高い入射エネルギーで測定されたデータと比較することで、同位体生成断面積の入射エネルギー依存性を調査した。さらに、測定データをPHITS, SPACS, EPAX, DEURACSの計算値と比較した。本研究で測定したデータは、理論計算の良いベンチマークになると考えられる。
Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; 緒方 一介*; 吉田 数貴; Authelet, G.*; et al.
Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03
被引用回数:12 パーセンタイル:74.01(Physics, Nuclear)中性子過剰核であるCoに対する(
)ノックアウト反応が理化学研究所RIBFで測定された。
coincidenceの方法で準位構造が決定され、測定された包括的断面積および排他的断面積から暫定的ではあるがスピン・パリティが決定された。殻模型計算との比較により、
Coの低励起状態には球形核と変形核が共存することが示唆された。
Elekes, Z.*; Kripk,
*; Sohler, D.*; Sieja, K.*; 緒方 一介*; 吉田 数貴; Doornenbal, P.*; Obertelli, A.*; Authelet, G.*; 馬場 秀忠*; et al.
Physical Review C, 99(1), p.014312_1 - 014312_7, 2019/01
被引用回数:12 パーセンタイル:71.31(Physics, Nuclear)(,
)反応による
Niの核構造の探索実験を行った。Lenzi, Nowacki, Poves, Sieja相互作用を用いた殻模型計算では実験結果を説明しうる陽子空孔状態が得られており、理論的な断面積計算は実験値とよい一致を与えた。実験で得られたすべての状態を理論的に一意に決定することはできなかったが、過去の実験結果と同様にNi同位体でのZ = 28の大きなshell gapを示す結果が得られた。
Shand, C. M.*; Podolyk, Zs.*; G
rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.
Physics Letters B, 773, p.492 - 497, 2017/10
被引用回数:28 パーセンタイル:87.72(Astronomy & Astrophysics)Low-lying states in neutron-rich Zn nuclei were measured for the first time via in-beam
-ray spectroscopy at RIKEN. These include the 4
to 2
in
Zn and the 2
to 0
and 4
to 2
in
Zn. The reduced E(
) energies and increased E(4
)/E(2
) ratios at
=52,54 compared to
Zn attest that the magicity is confined just on the neutron number
=50 only. The levels observed in
Zn suggest the onset of deformation towards heavier Zn isotopes. The data were compared to state-of-the-art shell model calculations.
籾山 悟至*; Doornenbal, P.*; Scheit, H.*; 武内 聡*; 新倉 潤*; 青井 考*; Li, K.*; 松下 昌史*; Steppenbeck, D.*; Wang, H.*; et al.
Physical Review C, 96(3), p.034328_1 - 034328_8, 2017/09
被引用回数:6 パーセンタイル:43.15(Physics, Nuclear)理化学研究所の不安定核実験施設RIBFにて、中性子過剰核Mgの励起状態を
Mgおよび
Alからのノックアウト反応によって生成し、そこからの脱励起
線を観測した。
Mgは中性子数20魔法数が消滅するとされる「逆転の島」と呼ばれる領域に含まれると考えられており、また、奇核であることから、一粒子状態と集団的状態が結合した興味深い核構造が出現すると期待されている。この実験によって、206keV, 443keV, 616keV, 670keVの4本の
線を観測し、これらを全て基底状態へ脱励起する
線であると仮定して励起準位を構成した。この準位構造、ノックアウト反応の断面積、移行運動量分布を殻模型計算および反対称化分子動力学計算と比較した。二つの計算は、基底状態近傍の高い準位密度などいくつかの特徴的な核構造を再現することに成功し、
Mgは「逆転の島」に含まれるという描像と無矛盾であることがわかった。
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physics Letters B, 772, p.483 - 488, 2017/09
被引用回数:8 パーセンタイル:52.04(Astronomy & Astrophysics)A new high-spin isomer in the neutron-rich nucleus Cd was populated in the projectile fission of a
U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T
= 6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15
). The isomeric state decays via the emission of a 309-keV
ray with
multipolarity. The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus
Cd. The comparison with calculations shows that adjustments of the pairing and multipole parts of the effective interaction derived from the CD-Bonn nucleon-nucleon potential are required in order to describe the properties of nuclei in the region around
Sn.
Flavigny, F.*; Doornenbal, P.*; Obertelli, A.*; Delaroche, J.-P.*; Girod, M.*; Libert, J.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; et al.
Physical Review Letters, 118(24), p.242501_1 - 242501_6, 2017/06
被引用回数:40 パーセンタイル:86.20(Physics, Multidisciplinary)The first -ray spectroscopy of very neutron rich
Kr isotopes was carried out at the RIBF at RIKEN Nishina center. Excited states in these isotopes were populated via (p,2p) reactions using radioactive
Rb beams accelerated to 220 MeV/nucleon. The new data show a significant increase in deformation beyond N=60, as well as competing configurations (shape-coexistence) at low energy. The data were compared with beyond-mean-field calculations which predict level energies in good agreement with observation, and suggest oblate-prolate shape coexistence.
Vaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; Ncher, E.*; Sahin, E.*; 志賀 慶明*; et al.
Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05
被引用回数:23 パーセンタイル:76.21(Physics, Multidisciplinary)Excited states in Sn were populated following one-neutron knockout reaction from an unstable
Sn beam at the RIBF laboratory in RIKEN. In addition to the already known
rays, additional
strength was observed for the first time in the excitation-energy range 3.5-5.5 MeV. Since the neutron separation energy of
Sn is low, this observation provides direct evidence for the radioactive decay of neutron-unbound states in this nucleus. The ability of
decay to compete with neutron emission was attributed to a mismatch between the wave functions of the initial and final states in the neutron emission case. These findings suggest that in the region south-east of
Sn, nuclear structure effects play a significant role in the decay of unbound states, which are instead usually ignored in the evaluation of neutron-emission probabilities in astrophysical simulations.
Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Rodriguez, T. R.*; Authelet, G.*; 馬場 秀忠*; Calvet, D.*; Chteau, F.*; Corsi, A.*; Delbart, A.*; et al.
Physical Review C, 95(4), p.041302_1 - 041302_6, 2017/04
被引用回数:31 パーセンタイル:89.36(Physics, Nuclear)Neutron-rich isotopes of selenium, Se, where studied via in beam
-ray spectroscopy after nucleon removal reactions at RIBF in RIKEN. The low-energy excitations of these nuclei were investigated using
-
coincidences, and the first and second excited 2
states were found at remarkably low energies. The analysis and comparison with self-consistent beyond-mean field calculations suggest that both shape coexistence and triaxiality are needed to describe these isotopes.
Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 角田 佑介*; Otsuka, T.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; et al.
Physics Letters B, 765, p.328 - 333, 2017/02
被引用回数:38 パーセンタイル:92.42(Astronomy & Astrophysics)The level schemes of neutron-rich isotopes Co and
Ni were populated in the
decay of
Fe and studied using
-delayed
-ray spectroscopy of the
decay, at the RIBF in RIKEN, Japan. The experimental results were compared to state-of-the-art shell-model calculations, and indicate a dominance of prolate deformation in the low-lying states, coexisting with spherical states. The
decay of the
isobars is shown to progress in accordance to a new type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.
Paul, N.*; Corsi, A.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Bally, B.*; Bender, M.*; Calvet, D.*; Chteau, F.*; et al.
Physical Review Letters, 118(3), p.032501_1 - 032501_7, 2017/01
被引用回数:46 パーセンタイル:88.19(Physics, Multidisciplinary)The first measurement of rays emitted by the very neutron rich nuclei
Mo (Z=42) and
Zr (Z=40) was carried out at the RIBF facility at RIKEN. These data shine light on the postulated N=70 harmonic oscillator shell. If the spin-orbit splitting which gives rise to the N=82 shell gap is reduced in very neutron-rich nuclei, the harmonic oscillator gap at N=70 should open instead. However, both the measured energy of the first excited state
Mo and
Zr, respectively 235(7) keV and 185(11) keV, and their E(4
)/E(2
) ratio, indicate that these nuclei are good rotors, and exclude the shell stabilization scenario at Z=40 and N=70. These results were compared to state-of-the-art density functional theoretical calculations using Gogny and Skyrme effective interactions.
Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P. A.*; 炭竃 聡之*; Taprogge, J.*; Xu, Z. Y.*; et al.
Physical Review C, 94(2), p.024303_1 - 024303_8, 2016/08
被引用回数:19 パーセンタイル:75.93(Physics, Nuclear)The decay of the semi-magic nucleus
Cd has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of
In and the observation of additional
feeding to high lying core-excited states in
In. The experimental results are compared to shell-model calculations employing a model space consisting of the full major
neutron and
proton shells, and good agreement is found.
Morales, A. I.*; Benzoni, G.*; Watanabe, H.*; 西村 俊二*; Browne, F.*; Daido, R.*; Doornenbal, P.*; Fang, Y.*; Lorusso, G.*; Patel, Z.*; et al.
Physical Review C, 93(3), p.034328_1 - 034328_14, 2016/03
被引用回数:26 パーセンタイル:83.44(Physics, Nuclear)Low-lying excited states in Ni have been investigated at RIKEN by studying the
decay of
Co to
Ni.
Co was separated with BigRIPS, implanted into the WaS3ABi Silicon array, and the
ray measured using the EURICA
spectrometer. From the analysis, 60 new
-ray transitions and 21 new levels in
Ni were observed. The new experimental information is compared to shell-model calculations which include neutron excitation across the
shell. The calculations reproduce rather well the observed states, implying that a clear understanding of these low-lying excitations has been achieved.
Benzoni, G.*; Morales, A. I.*; Watanabe, H.*; 西村 俊二*; Coraggio, L.*; Itaco, N.*; Gargano, A.*; Browne, F.*; Daido, R.*; Doornenbal, P.*; et al.
Physics Letters B, 751, p.107 - 112, 2015/12
被引用回数:20 パーセンタイル:75.34(Astronomy & Astrophysics)The decays of
Mn have been measured at the RIBF facility at RIKEN using the EURICA
spectrometer combined with an active stopper consisting of a stack of Si detectors. Half-lives and
-delayed neutron emission probabilities have been extracted for these decays, together with first experimental information on excited states populated in
Fe. The data indicate a continuously increasing deformation for Fe isotopes up to A=70, and interpreted to be due to the interplay between quadrupole correlation of specific neutron orbitals and the monopole component of the proton-neutron interaction.
郷 慎太郎*; 井手口 栄治*; 横山 輪*; 小林 幹*; 木佐森 慶一*; 高木 基伸*; 宮 裕之*; 大田 晋輔*; 道正 新一郎*; 下浦 享*; et al.
JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06
The high-spin states in S were investigated at Tandem-ALTO facility in Institut de Physique Nucl
aire d'Orsay The
Mg(
O, 2
1n)
S fusion evaporation reaction was used to populate high-spin states in
S. The germanium
-ray detector array ORGAM was employed to measure
rays from high-spin states and charged particles evaporated from the compound nuclei were detected by a segmented silicon detector, Si-Ball. A level scheme for
S was deduced based on the gamma-gamma-coincidence analysis and
-ray angular correlation analysis. The half-life of the transition in the superdeformed band was estimated by measuring the residual Doppler shift. The deduced half-life shows the large collectivity of the band.
Taprogge, J.*; Jungclaus, A.*; Grawe, H.*; 西村 俊二*; Doornenbal, P.*; Lorusso, G.*; Simpson, G. S.*; Sderstr
m, P.-A.*; 炭竃 聡之*; Xu, Z. Y.*; et al.
Physical Review C, 91(5), p.054324_1 - 054324_11, 2015/05
被引用回数:24 パーセンタイル:80.08(Physics, Nuclear)The decay of
Cd, produced in relativistic fission of a
U beam, was studied at the RIKEN Nishina Center. From the
-ray analysis, 31 excited states and 69
ray transitions were established in the level scheme of
In, and compared with state-of-the-art shell-model calculations. It was found that the
decay of
Cd is dominated by Gamow teller transitions, but a non-negligible contribution to the
decay is also made by first-forbidden transitions. To estimate the contribution of first-forbidden transitions is important for calculations of the
-decay half-lives of nuclei in this region.