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Venhart, M.*; Balogh, M.*; Herz, A.*; Wood, J. L.*; Ali, F. A.*; Joss, D. T.*; Andreyev, A. N.; Auranen, K.*; Carroll, R. J.*; Drummond, M. C.*; et al.
Physics Letters B, 806, p.135488_1 - 135488_6, 2020/07
The extremely neutron-deficient isotopes Au were studied by means of in-beam
-ray spectroscopy. Specific tagging techniques,
-decay tagging in
Au and isomer tagging in
Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2
and 3
proton-hole configurations, from the 1
proton-intruder configuration was observed in
Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.
Kim, H.-J.*; Gubler, P.
Physics Letters B, 805, p.135412_1 - 135412_8, 2020/06
被引用回数:1 パーセンタイル:100(Astronomy & Astrophysics)QCD和則を利用し、核物質におけるメソンの分散関係を調べる。敗れたLorentz対称性により、有限密度中ではベクター粒子のlongitudinal及びtransverseモードが異なる振る舞いを示しえる。次元6までの可能な演算子及びそのWilson係数をすべて用い、様々な密度及び運動量における
メソンの分散関係を解析する。その結果、longitudinal及びtransverseモードが逆の振る舞いを示すことが分かった。実際、運動量1GeVでは、longitudinalモードでは質量が5MeVほど下り、transverseモードでは7MeVほど上がることが分かった。longitudinal及びtransverseモードを区別しない実験では、この現象が二つの分離されたピークとして観測される可能性がある。
Sun, Y. L.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; 茶園 亮樹*; Duguet, T.*; Liu, H. N.*; Navrtil, P.*; Nowacki, F.*; 緒方 一介*; et al.
Physics Letters B, 802, p.135215_1 - 135215_7, 2020/03
被引用回数:2 パーセンタイル:13.44(Astronomy & Astrophysics)カリウムは陽子数が19であるため、その,
状態はそれぞれ陽子の
,
軌道の空孔状態によって支配されている。その中性子数を
から増やすとこの2つの準位のエネルギー差
は大きく変化することが知られており、中性子過剰核における殻進化と呼ばれる現象のプロトタイプとなっている。これまで
は
まで知られていたが、この研究では、理化学研究所RIビームファクトリーにて、カルシウム同位体からの陽子ノックアウト反応によって
Kの励起状態を生成し、そこからの脱励起ガンマ線を測定することによって、
における
を測定することに成功した。歪曲波インパルス近似計算と実験で得られた断面積の比較から、
,
状態は空孔状態によって支配されていることを確かめた。
の値は
で最小となり、そこから中性子数を増やすとともに増大することがわかった。これは、中心力とテンソル力による殻進化描像にしたがった振る舞いである。
Corts, M. L.*; Rodriguez, W.*; Doornenbal, P.*; Obertelli, A.*; Holt, J. D.*; Lenzi, S. M.*; Men
ndez, J.*; Nowacki, F.*; 緒方 一介*; Poves, A.*; et al.
Physics Letters B, 800, p.135071_1 - 135071_7, 2020/01
被引用回数:3 パーセンタイル:13.44(Astronomy & Astrophysics)ガンマ線分光による=40同調体である
Tiの分光学研究を
V(
,
)
TiをRIBFで行った。今回初めて測定された
と
の遷移はTiの基底状態が変形していることを示唆した。これらのエネルギーは近傍核の
Crや
Feと比較して大きく、したがって四重極集団運動が小さくなっていることが示唆される。今回の結果は大規模殻模型計算によって良く再現される一方、第一原理計算や平均場模型では今回の結果は再現されなかった。
Sun, M. D.*; Liu, Z.*; Huang, T. H.*; Zhang, W. Q.*; Andreyev, A. N.; Ding, B.*; Wang, J. G.*; Liu, X. Y.*; Lu, H. Y.*; Hou, D. S.*; et al.
Physics Letters B, 800, p.135096_1 - 135096_5, 2020/01
被引用回数:1 パーセンタイル:30.54(Astronomy & Astrophysics)Fine structure in the decay of
U was observed in the fusion-evaporation reaction
Re(
Ar,p3n) by using fast digital pulse processing technique. Two
-decay branches of
U feeding the ground state and 244 keV excited state of
Th were identified by establishing the decay chain
U
Th
Ra
Rn. The
-particle energy for the ground-state to ground-state transition of
U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62
s. Evolution of nuclear structure for
=131 even-
isotones from Po to U was discussed in the frameworks of nuclear mass and reduced
-decay width, a weakening octupole deformation in the ground state of
U relative to its lighter isotones
Ra and
Th was suggested.
Meng, Q.*; 肥山 詠美子*; Can, K. U.*; Gubler, P.; 岡 眞; 保坂 淳; Zong, H.*
Physics Letters B, 798, p.135028_1 - 135028_8, 2019/11
被引用回数:0Several compact pentaquark resonances are predicted in a potential quark model. The Hamiltonian is the best available one, which reproduces the masses of the low-lying charmed and strange hadrons well. Full five-body calculations are carried out by the use of the Gaussian expansion method, and the relevant baryon-meson thresholds are taken into account explicitly. Employing the real scaling method, we predict four sharp resonances,
(
= 5180 MeV,
= 20 MeV) and others. These are the candidates of compact pentaquark resonance states from the current best quark model, which should be confirmed either by experiments or lattice QCD calculations.
Meng, Q.*; 肥山 詠美子; Can, K. U.*; Gubler, P.; 岡 眞; 保坂 淳; Zong, H.*
Physics Letters B, 798, p.135028_1 - 135028_8, 2019/11
被引用回数:3 パーセンタイル:41(Astronomy & Astrophysics)Several compact pentaquark resonances are predicted in a potential quark model. The Hamiltonian is the best available one, which reproduces the masses of the low-lying charmed and strange hadrons well. Full five-body calculations are carried out by the use of the Gaussian expansion method, and the relevant baryon-meson thresholds are taken into account explicitly. Employing the real scaling method, we predict four sharp resonances. These are the candidates of compact pentaquark resonance states from the current best quark model, which should be confirmed either by experiments or lattice QCD calculations.
若山 将征*; 保坂 淳
Physics Letters B, 795, p.548 - 553, 2019/08
被引用回数:2 パーセンタイル:41(Astronomy & Astrophysics)We study the Lee-Yang zeros in the canonical approach to search phase transition points at finite temperature and density in the Nambu-Jona-Lasinio (NJL) model as an effective model of QCD. The canonical approach is a promising method to avoid the sign problem in lattice QCD at finite density. We find that a set of Lee-Yang zeros computed with finite degrees of freedom can be extrapolated to those with infinite degrees of freedom, providing the correct phase transition point. We propose the present method as a useful method for actual lattice simulations for QCD.
Shim, S.-I.*; 保坂 淳; Kim, H.-C.*
Physics Letters B, 795, p.438 - 445, 2019/08
被引用回数:1 パーセンタイル:63.02(Astronomy & Astrophysics)We study the vector and axial-vector form factors of radiative kaon decay within the framework of the gauged nonlocal effective chiral action from the instanton vacuum, focusing on the effects of flavor SU(3) symmetry breaking. The general tendency of the results are rather similar to those of radiative pion decays: The nonlocal contributions make the results of the vector form factor increased by about 20%, whereas they reduce those of the axial-vector form factor by almost 50%. Suppressing the prefactors consisting of the kaon mass and the pion decay constant, we scrutinize how the kaon form factors undergo changes as the mass of the strange current quark is varied. Those related to the vector and second axial-vector form factors tend to decrease monotonically as the strange quark mass increases, whereas that for the axial-vector form factor decreases. When decay is considered, both the results of the vector and axial-vector form factors at the zero momentum transfer are in good agreement with the experimental data. The results are also compared with those from chiral perturbation theory to
order.
Vaquero, V.*; Jungclaus, A.*; Rodrguez-S
nchez, J. L.*; Tostevin, J. A.*; Doornenbal, P.*; Wimmer, K.*; Chen, S.*; Orlandi, R.; 他26名*
Physics Letters B, 795, p.356 - 361, 2019/08
被引用回数:2 パーセンタイル:63.02(Astronomy & Astrophysics)Inclusive one- and multi-nucleon removal cross sections were measured for several Sn, Sb and Te isotopes beyond the = 82 neutron shell closure at RIBF, RIKEN. The experimental cross sections are compared to predictions from the most recent Liege intranuclear cascade model. Severe discrepancies are observed and are discussed. Also, the measured inclusive one-proton knockout cross section for the semi-magic
Sn projectile is compared to eikonal direct reaction theory calculations to assess if the suppression factors to these calculated cross sections are applicable to heavy nuclei.
Berry, T. A.*; Podolyk, Zs.*; Carroll, R. J.*; Lic
, R.*; Grawe, H.*; Timofeyuk, N. K.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; et al.
Physics Letters B, 793, p.271 - 275, 2019/06
被引用回数:1 パーセンタイル:63.02(Astronomy & Astrophysics)Gamow-Teller decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This
= 0 requirement plays a major role in the
decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical
-process pathway below both
= 50 (for
82) and
= 82 (for
126). The level of forbiddenness of the
= 1
1
0
transition has been investigated from the
decay of the ground state of
Hg into the single-proton-hole nucleus
Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible
-ray transitions depopulating the
0
state in
Tl, an upper limit of 3.9
10
% was obtained for the probability of this decay, corresponding to log
8.8 within a 95% confidence limit. This is the most stringent test of the
= 0 selection rule to date.
渡邉 寛*; Wang, H. K.*; Lorusso, G.*; 西村 俊二*; Xu, Z. Y.*; 炭竃 聡之*; Orlandi, R.; 他47名*
Physics Letters B, 792, p.263 - 268, 2019/05
被引用回数:1 パーセンタイル:63.02(Astronomy & Astrophysics)The isotopes Pd and
Pd, respectively with 79 and 81 neutrons, are key isotopes to understand the evolution of the N=82 shell closure below
Pd. These nuclei were studied at RIBF (RIKEN). New isomeric states with half-lives of 144(4) ns and 39(6)
s were assigned spins and parities of (23/2
) and (19/2
) in
Pd and
Pd, respectively. The assignment was carried out based on the results of the
-ray intensity balance analysis and the measured transition strengths with the aid of a shell-model calculation. The isomoer in
Pd was ascribed predominantly to three neutron-hole excitations in the N=50-82 shell. The 19/2
state in
Pd is expected to involve the coupling of proton and neutron configurations. The new data will provide important benchmarks for a better understanding of
-process nucleosynthesis.
岩崎 幸生; 岡 眞; 鈴木 渓*; 吉田 哲也*
Physics Letters B, 790, p.71 - 76, 2019/03
被引用回数:3 パーセンタイル:27.46(Astronomy & Astrophysics)ヘビークォークを含むメソンに強い磁場がかかったときにスペクトルおよび波動関数がどのように変化するかを磁場の強さの関数として解析した。
Tsekhanovich, I.*; Andreyev, A. N.; 西尾 勝久; Denis-Petit, D.*; 廣瀬 健太郎; 牧井 宏之; Matheson, Z.*; 森本 幸司*; 森田 浩介*; Nazarewicz, W.*; et al.
Physics Letters B, 790, p.583 - 588, 2019/03
被引用回数:10 パーセンタイル:6.44(Astronomy & Astrophysics)Fragment mass distributions from fission of the excited compound nucleus Pt have been deduced from the measured fragment velocities. The
Pt nucleus was created at the JAEA tandem facility in a complete fusion reaction
Ar+
Nd, at beam energies of 155, 170 and 180 MeV. The data are indicative of a mixture of the mass-asymmetric and mass-symmetric fission modes associated with higher and lower total kinetic energies of the fragments, respectively. The measured fragment yields are dominated by asymmetric mass splits, with the symmetric mode contributing at the level of
1/3. This constitutes the first observation of a multimodal fission in the sub-lead region. Most probable experimental fragment-mass split of the asymmetric mode,
/
79/99, is well reproduced by nuclear density functional theory using the UNEDF1-HFB and D1S potentials. The symmetric mode is associated by theory with very elongated fission fragments, which is consistent with the observed total kinetic energy/fragment mass correlation.
Lederer-Woods, C.*; Battino, U.*; Ferreira, P.*; Gawlik, A.*; 木村 敦; n_TOF Collaboration*; 他128名*
Physics Letters B, 790, p.458 - 465, 2019/03
被引用回数:1 パーセンタイル:63.02(Astronomy & Astrophysics) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at
=30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of
Ge produced in stars, which would explain the low isotopic abundance of
Ge in the solar system.
橋本 直; 谷田 聖; 他67名*
Physics Letters B, 789, p.620 - 625, 2019/02
被引用回数:15 パーセンタイル:1.75(Astronomy & Astrophysics)における
不変質量分布において
、つまり
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。
= 350
650MeV/
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(
)に続いて残りの2各紙に吸収される反応(
)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
MeV、幅
MeV、そして
波ガウス形状因子パラメータ
MeV/
という値が"
"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。
Cubiss, J. G.*; Barzakh, A. E.*; Andreyev, A. N.; 他57名*
Physics Letters B, 786, p.355 - 363, 2018/11
被引用回数:11 パーセンタイル:12.74(Astronomy & Astrophysics)The first accurate measurements of the -decay branching ratio and half-life of the I
=1/2
ground state in
Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in
Au. The results are discussed within the complementary systematics of the reduced
-decay widths and nuclear g factors of low-lying, I
=1/2
states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2
1/2
,
Tl
Au
decay, which is explained by a mixing of
3s
and
2d
configurations in
Au
, whilst
Tl
remains a near-pure
3s
. This conclusion is inferred from the g factor of
Au
which has an intermediate value between those of
3s
and
2d
states. A similar mixed configuration is proposed for the I
=1/2
ground state of
Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.
Orlandi, R.; Pain, S. D.*; Ahn, S.*; Jungclaus, A.*; Schmitt, K. T.*; Bardayan, D. W.*; Catford, W. N.*; Chapman, R.*; Chipps, K. A.*; Cizewski, J. A.*; et al.
Physics Letters B, 785, p.615 - 620, 2018/10
被引用回数:5 パーセンタイル:39.37(Astronomy & Astrophysics)Low-lying neutron-hole states in Sn were populated via the
Sn(d,t) reaction at Oak Ridge National Laboratory. The triton angular distributions were compared to DWBA calculations and revealed spectroscopic factors compatible with a single-hole nature of the states populated. The data permit to determine the spin-orbit splitting of the strongly bound
and
neutron orbits below the shell gap, which was compared to the splitting of the weakly bound 3
and 2
orbits above the gap. The comparison revealed a smaller energy splitting of the 3
orbits. All splittings were reproduced using Woods-Saxon calculations, and the lower splitting of the 3
orbits was explained to arise from the large radial extent of the wavefunction and small value of the amplitude at the surface. This result is important to understand at a fundamental level the spin-orbit interaction, and its effects on neutron-rich nuclei.
Xu, Z. Y.*; Heylen, H.*; 旭 耕一郎*; Boulay, F.*; Daugas, J. M.*; de Groote, R. P.*; Gins, W.*; Kamalou, O.*; Koszors,
.*; Lykiardopoupou, M.*; et al.
Physics Letters B, 782, p.619 - 626, 2018/07
被引用回数:3 パーセンタイル:78.75(Astronomy & Astrophysics)GANIL研究所において、Sからのフラグメンテーション反応によって中性子過剰核
Alにおける核異性体である
状態を生成し、その磁気双極子モーメントと電気的四重極モーメント(Qモーメント)をそれぞれ
-NMR法および
-NQR法を用いて測定した。この状態は中性子数20の殻ギャップを越えて励起したものであり、その性質を実験的に押さえることは、この原子核の周辺で知られている逆転の島(基底状態で既に殻ギャップを越えた励起が起こるとされる原子核の一団)の発現のメカニズムを解明するための有益な情報を与える。測定されたg因子の絶対値は
、Qモーメントの絶対値は38(5)mbとなった。これらの値は、大規模殻模型計算による予言値に近く、模型の高い記述能力を確かめることができた。
Morales, A. I.*; Orlandi, R.; 他61名*
Physics Letters B, 781, p.706 - 712, 2018/06
被引用回数:10 パーセンタイル:15.06(Astronomy & Astrophysics)By studying the decay of the radioactive nuclei
Co and
Co produced at RIBF, RIKEN, the low-lying excited states in
Ni were studied for the first time up to spin 8
. These states originate from the valence neutrons occupying the
orbit, and permit to investigate the seniority quantum number. The data reveal that the seniority isomerism of the 8
state disappears, and this phenomenon is explained by comparison with shell model calculations and the influence of spherical doubly-magic
Ni.