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論文

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

https://doi.org/10.1103/PhysRevLett.123.061103

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.

論文

Localized magnetic excitations in the fully frustrated dimerized magnet Ba$$_{2}$$CoSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$

栗田 伸之*; 山本 大輔*; 金坂 拓哉*; 古川 信夫*; 河村 聖子; 中島 健次; 田中 秀数*

Physical Review Letters, 123(2), p.027206_1 - 027206_6, 2019/07

https://doi.org/10.1103/PhysRevLett.123.027206

Magnetic excitations of the effective spin $$S$$ =1/2 dimerized magnet Ba$$_{2}$$CoSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$ have been probed directly via inelastic neutron scattering experiments. We observed five types of excitation, which are all dispersionless within the resolution limits. The scattering intensities of the three low-lying excitations were found to exhibit different $$Q$$-dependences. Detailed analysis has demonstrated that Ba$$_{2}$$CoSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$ is a two dimensional spin dimer system described only by a single dimer site, where the triplet excitations are localized owing to the almost perfect frustration of the interdimer exchange interactions and the undimerized spins, even in small concentration, make an essential contribution to the excitation spectrum.

論文

Emergence of a complete heavy-quark spin symmetry multiplet; Seven molecular pentaquarks in light of the latest LHCb analysis

Liu, M.-Z.*; Pan, Y.-W.*; Peng, F.-Z.*; S$'a$nchez-S$'a$nchez, M.*; Geng, L.-S.*; 保坂 淳; Valderrama, M. P.*

Physical Review Letters, 122(24), p.242001_1 - 242001_5, 2019/06

https://doi.org/10.1103/PhysRevLett.122.242001

A recent analysis by the LHCb Collaboration suggests the existence of three narrow pentaquarklike states-the $$P_c$$(4312), $$P_c$$(4440), and $$P_c$$(4457)-instead of just one in the previous analysis [the $$P_c$$(4450)]. The closeness of the $$P_c$$(4312) to the $$bar{D}^{*}Sigma_c$$ threshold and the $$P_c$$(4440) and $$P_c$$(4457) to the $$bar{D}^{*}Sigma_c$$ threshold suggests a molecular interpretation of these resonances. We show that these three pentaquarklike resonances can be naturally accommodated in a contact-range effective field theory description that incorporates heavy-quark spin symmetry. This description leads to the prediction of all the seven possible $$S$$-wave heavy antimeson-baryon molecules [that is, there should be four additional molecular pentaquarks in addition to the $$P_c$$(4312), $$P_c$$(4440), and $$P_c$$(4457)], providing the first example of a heavy-quark spin symmetry molecular multiplet that is complete. If this is confirmed, it will not only give us an impressive example of the application of heavy-quark symmetries and effective field theories in hadron physics, it will also uncover a clear and powerful ordering principle for the molecular spectrum, reminiscent of the SU(3)-flavor multiplets to which the light hadron spectrum conforms.

論文

Topological characterization of classical waves; The Topological origin of magnetostatic surface spin waves

山本 慧; Thiang, G. C.*; Pirro, P.*; Kim, K.-W.*; Everschor-Sitte, K.*; 齊藤 英治*

Physical Review Letters, 122(21), p.217201_1 - 217201_5, 2019/05

https://doi.org/10.1103/PhysRevLett.122.217201

We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriately reformulated for these classical waves, we predict that surface modes appear but not in a gap of the bulk frequency spectrum. This feature, consistent with the magnetostatic surface spin waves, indicates a broader realm of topological phases of matter beyond spectrally gapped ones.

論文

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

https://doi.org/10.1103/PhysRevLett.122.217003

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.

論文

Proton shell evolution below $$^{132}$$Sn; First measurement of low-lying $$beta$$-emitting isomers in $$^{123,125}$$Ag

Chen, Z. Q.*; Li, Z. H.*; Hua, H.*; 渡邉 寛*; Yuan, C. X.*; Zhang, S. Q.*; Lorusso, G.*; Orlandi, R.; 他60名*

Physical Review Letters, 122(21), p.212502_1 - 212502_6, 2019/05

https://doi.org/10.1103/PhysRevLett.122.212502

$$beta$$-delayed $$gamma$$-ray spectroscopy of the neutron-rich isotopes $$^{123,125}$$Ag was carried out at RIBF, RIKEN. The long predicted 1/2$$^{-}$$ $$beta$$ emitting isomers were identified in both nuclei for the first time. The new experimental results extend the systematic trend of energy spacing between the lowest 9/2$$^+$$ and 1/2$$^{-}$$ levels in Ag isotopes up to N=78, providing a clear signal for the reduction of the Z=40 subshell gap in Ag towards N=82. The tensor force is found to play a key role in the reduction of the Z=40 sub-shell gap.

論文

Prominence of pairing in inclusive ($$p,2p$$) and ($$p,pn$$) cross sections from neutron-rich nuclei

Paul, N.*; Obertelli, A.*; Bertulani, C. A.*; Corsi, A.*; Doornenbal, P.*; Rodriguez-Sanchez, J. L.*; Authelet, G.*; Orlandi, R.; 他84名*

Physical Review Letters, 122(16), p.162503_1 - 162503_7, 2019/04

https://doi.org/10.1103/PhysRevLett.122.162503

Fifty-five single nucleon removal cross sections from neutron-rich nuclei impinging on a hydrogen target at about 250 MeV/nucleon were measured at the RIKEN RIBF. Systematically higher cross sections are found for proton removal from nuclei with an even number of protons compared to odd-proton number projectiles for the same separation energy, while no even-odd staggering was observed in case of neutron-removal. These observations are linked to paring correlations in the daughter nuclei and the density of bound levels. The effect is particularly strong in loosely bound nuclei.

論文

Tunable magnonic thermal Hall effect in skyrmion crystal phases of ferrimagnets

Kim, S. K.*; 仲田 光樹; Loss, D.*; Tserkovnyak, Y.*

Physical Review Letters, 122(5), p.057204_1 - 057204_6, 2019/02

https://doi.org/10.1103/PhysRevLett.122.057204

フェリ磁性スカーミオン結晶中のトポロジカルマグノンホール効果、およびその熱制御方法を理論的に提案する。

論文

Strong correlation between ferromagnetic superconductivity and pressure-enhanced ferromagnetic fluctuations in UGe$$_2$$

立岩 尚之; 芳賀 芳範; 山本 悦嗣

Physical Review Letters, 121(23), p.237001_1 - 237001_6, 2018/12

https://doi.org/10.1103/PhysRevLett.121.237001
 被引用回数：1 パーセンタイル：49.95(Physics, Multidisciplinary)

ウラン系強磁性超伝導物質UGe$$_2$$の高圧下磁化測定を行い、データをTakahashiによるスピンのゆらぎ理論を用いて解析した。強磁性相FM1とFM2の相境界$$P_x$$で、スピンゆらぎスペクトルの分布幅$$T_0$$に明確な異常が現れた。$$P_x$$では、超伝導転移温度$$T_{rm sc}$$が最大値を示す。このことは、$$P_x$$近辺で発達する強磁性スピンのゆらぎが超伝導出現に役割を果たすことを示唆する。また、パラメーター$${T_{rm Curie}}/{T_0}$$(ここで、$${T_{rm Curie}}$$は強磁性転移温度)の圧力変化から、局在性の強いFM2から遍歴性の強いFM1へ基底状態は転移することが示唆された。$$T_0$$と$$T_{rm sc}$$の関係について、銅酸化物超伝導体等、他の超伝導物質と議論された。

論文

First evidence for cos 2$$beta >$$ 0 and resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle ambiguity

足立 一郎*; 谷田 聖; Belle Collaboration*; 他421名*

Physical Review Letters, 121(26), p.261801_1 - 261801_11, 2018/12

https://doi.org/10.1103/PhysRevLett.121.261801
 被引用回数：1 パーセンタイル：49.95(Physics, Multidisciplinary)

We present first evidence that the cosine of the $$CP$$-violating weak phase $$2beta$$ is positive, and hence exclude trigonometric multifold solutions of the CKM Unitarity Triangle using a time-dependent Dalitz plot analysis of $$B^{0} to D^{(*)} h^{0}$$ with $$D to K_{S}^{0} pi^{+} pi^{-}$$ decays, where $$h^{0} in {pi^{0}, eta, omega }$$ denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BaBar and Belle experiments collected at the $$Upsilon(4S)$$ resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain $$( 471 pm 3 )times 10^6, Bbar{B}$$ pairs recorded by the BaBar detector and $$( 772 pm 11 )times 10^6, Bbar{B}$$ pairs recorded by the Belle detector. The results of the measurement are $$sin{2beta} = 0.80 pm 0.14 ,(rm{stat.}) pm 0.06 ,(rm{syst.}) pm 0.03 ,(rm{model})$$ and $$cos{2beta} = 0.91 pm 0.22 ,(rm{stat.}) pm 0.09 ,(rm{syst.}) pm 0.07 ,(rm{model})$$. The result for the direct measurement of the angle $$beta$$ of the CKM Unitarity Triangle is $$beta = left( 22.5 pm 4.4 ,(rm{stat.}) pm 1.2 ,(rm{syst.}) pm 0.6 ,(rm{model}) right)^{circ}$$. The quoted model uncertainties are due to the composition of the $$D^{0} to K_{S}^{0} pi^{+} pi^{-}$$ decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics $$e^{+}e^{-} to cbar{c}$$ data sample. CP violation is observed in $$B^{0} to D^{(*)} h^{0}$$ decays at the level of $$5.1$$ standard deviations. The significance for $$cos{2beta} > 0$$ is $$3.7$$ standard deviations. The trigonometric multifold solution $$pi/2 - beta = (68.1 pm 0.7)^{circ}$$ is excluded at the level of $$7.3$$ standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

論文

Observation of $$Upsilon(2S)togamma eta_{b}(1S)$$ decay

Fulsom, B. G.*; 谷田 聖; Belle Collaboration*; 他197名*

Physical Review Letters, 121(23), p.232001_1 - 232001_8, 2018/12

https://doi.org/10.1103/PhysRevLett.121.232001
 パーセンタイル：100(Physics, Multidisciplinary)

We report the observation of $$Upsilon(2S)togammaeta_{b}(1S)$$ decay based on analysis of the inclusive photon spectrum of $$24.7$$ fb$$^{-1}$$ of $$e^+ e^-$$ collisions at the $$Upsilon(2S)$$ center-of-mass energy collected with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider. We measure a branching fraction of $$mathcal{B}(Upsilon(2S)togammaeta_{b}(1S))=(6.1^{+0.6+0.9}_{-0.7-0.5})times 10^{-4}$$, and derive an $$eta_{b}(1S)$$ mass of $$9394.8^{+2.7+4.5}_{-3.1-2.7}$$ MeV/$$c^{2}$$, where the uncertainties are statistical and systematic, respectively. The significance of our measurement is greater than 7 standard deviations, constituting the first observation of this decay mode.

論文

Pseudorapidity dependence of particle production and elliptic flow in asymmetric nuclear collisions of $$p$$+Al, $$p$$+Au, $$d$$+Au, and $$^{3}$$He+Au at $$sqrt{s_{_{NN}}}$$ = 200 GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他362名*

Physical Review Letters, 121(22), p.222301_1 - 222301_8, 2018/11

https://doi.org/10.1103/PhysRevLett.121.222301
 被引用回数：3 パーセンタイル：29.91(Physics, Multidisciplinary)

Asymmetric nuclear collisions of $$p$$+Al, $$p$$+Au, $$d$$+Au, and $$^{3}$$He+Au at $$sqrt{s_{_{NN}}}$$ = 200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production $$dN_{rm ch}/deta$$ in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow $$v_{2}$$ over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.

論文

First accurate normalization of the $$beta$$-delayed $$alpha$$ decay of $$^{16}$$N and implications for the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O astrophysical reaction rate

Kirsebom, O. S.*; Tengblad, O.*; Andreyev, A.; 他41名*

Physical Review Letters, 121(14), p.142701_1 - 142701_6, 2018/10

https://doi.org/10.1103/PhysRevLett.121.142701

The $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction plays a central role in astrophysics, but its cross section at energies relevant for astrophysical applications is only poorly constrained by laboratory data. The reduced $$alpha$$ width, $$gamma_{rm 11}$$, of the bound 1$$^{-}$$ level in $$^{16}$$O is particularly important to determine the cross section. The magnitude of $$gamma_{11}$$ is determined via sub-Coulomb $$alpha$$-transfer reactions or the $$beta$$-delayed $$alpha$$ decay of $$^{16}$$N, but the latter approach is presently hampered by the lack of sufficiently precise data on the $$beta$$-decay branching ratios. Here we report improved branching ratios for the bound 1$$^{-}$$ level ($$b_{beta,11}$$) and for $$beta$$-delayed $$alpha$$ emission ($$b_{beta alpha}$$). Our value for $$b_{beta alpha}$$ is 33 $$%$$ larger than previously held, leading to a substantial increase in $$gamma_{11}$$. Our revised value for $$gamma_{11}$$ is in good agreement with the value obtained in $$alpha$$-transfer studies and the weighted average of the two gives a robust and precise determination of $$gamma_{11}$$, which provides significantly improved constraints on the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O cross section in the energy range relevant to hydro static He burning.

論文

Observation of an excited $$Omega^-$$ Baryon

Yelton, J.*; 谷田 聖; Belle Collaboration*; 他190名*

Physical Review Letters, 121(5), p.052003_1 - 052003_7, 2018/08

https://doi.org/10.1103/PhysRevLett.121.052003
 被引用回数：7 パーセンタイル：6.69(Physics, Multidisciplinary)

Using data recorded with the Belle detector, we observe a new excited hyperon, an $$Omega^{*-}$$ candidate decaying into $$Xi^0K^-$$ and $$Xi^-K^0_S$$ with a mass of $$2012.4pm0.7 {rm (stat)pm 0.6 (rm syst)} {rm MeV}/c^2$$ and a width of $$Gamma=6.4^{+2.5}_{-2.0} {rm(stat)}pm1.6 {rm(syst)} {rm MeV}$$. The $$Omega^{*-}$$ is seen primarily in $$Upsilon(1S), Upsilon(2S)$$, and $$Upsilon(3S)$$ decays.

論文

Observation of $$Upsilon(4S)to eta' Upsilon(1S)$$

Guido, E.*; 谷田 聖; Belle Collaboration*; 他168名*

Physical Review Letters, 121(6), p.062001_1 - 062001_7, 2018/08

https://doi.org/10.1103/PhysRevLett.121.062001
 パーセンタイル：100(Physics, Multidisciplinary)

We report the first observation of the hadronic transition $$Upsilon(4S)toeta'Upsilon(1S)$$, using 496 fb$$^{-1}$$ data collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^{+}e^{-}$$ collider. We reconstruct the $$eta'$$ meson through its decays to $$rho^0gamma$$ and to $$pi^+pi^-eta$$, with $$etatogammagamma$$. We measure: $${cal B}(Upsilon(4S)toeta'Upsilon(1S))=(3.43pm 0.88 {rm(stat.)} pm 0.21 {rm(syst.)})times10^{-5}$$, with a significance of 5.7$$sigma$$.

論文

Search for $$B^{-}tomu^{-}barnu_mu$$ decays at the Belle experiment

Sibidanov, A.*; 谷田 聖; Belle Collaboration*; 他187名*

Physical Review Letters, 121(3), p.031801_1 - 031801_8, 2018/07

https://doi.org/10.1103/PhysRevLett.121.031801
 被引用回数：3 パーセンタイル：20.01(Physics, Multidisciplinary)

We report the result of a search for the decay $$B^{-}tomu^{-}barnu_mu$$. The signal events are selected based on the presence of a high momentum muon and the topology of the rest of the event showing properties of a generic $$B$$-meson decay, as well as the missing energy and momentum being consistent with the hypothesis of a neutrino from the signal decay. We find a 2.4 standard deviation excess above background including systematic uncertainties, which corresponds to a branching fraction of $${cal B}(B^{-}tomu^{-}barnu_mu) =(6.46 pm 2.22 pm 1.60) times10^{-7}$$ or a frequentist 90% confidence level interval on the $$B^{-}tomu^{-}barnu_mu$$ branching fraction of $$[2.9, 10.7]times 10^{-7}$$. This result is obtained from a 711 fb$$^{-1}$$ data sample that contains $$772 times 10^6$$ $$Bbar{B}$$ pairs, collected near the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

$$^7$$Be(n,p)$$^7$$Li reaction and the cosmological lithium problem; Measurement of the cross section in a wide energy range at n_TOF at CERN

Damone, L.*; Barbagallo, M.*; Mastromarco, M.*; Cosentino, L.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他152名*

Physical Review Letters, 121(4), p.042701_1 - 042701_7, 2018/07

https://doi.org/10.1103/PhysRevLett.121.042701

We report on the measurement of the $$^7$$Be(n,p)$$^7$$Li cross section from thermal to approximately 325 keV neutron energy, performed in the high-flux experimental area (EAR2) of the n_TOF facility at CERN. This reaction plays a key role in the lithium yield of the big bang nucleosynthesis (BBN) for standard cosmology. The only two previous time-of-flight measurements performed on this reaction did not cover the energy window of interest for BBN, and they showed a large discrepancy between each other. The measurement was performed with a Si telescope and a high-purity sample produced by implantation of a $$^7$$Be ion beam at the ISOLDE facility at CERN. While a significantly higher cross section is found at low energy, relative to current evaluations, in the region of BBN interest, the present results are consistent with the values inferred from the time-reversal $$^7$$Li(p,n)$$^7$$Be reaction, thus yielding only a relatively minor improvement on the so-called cosmological lithium problem. The relevance of these results on the near threshold neutron production in the p+$$^7$$Li reaction is also discussed.

論文

Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe$$_{4}$$As$$_{4}$$

Xie, T.*; Wei, Y.*; Gong, D.*; Fennell, T.*; Stuhr, U.*; 梶本 亮一; 池内 和彦*; Li, S.*; Hu, J.*; Luo, H.*

Physical Review Letters, 120(26), p.267003_1 - 267003_7, 2018/06

https://doi.org/10.1103/PhysRevLett.120.267003
 被引用回数：3 パーセンタイル：20.01(Physics, Multidisciplinary)

We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFe$$_4$$As$$_4$$. In contrast to its quasi-two-dimensional electron structure, three strongly $$L$$-dependent modes of spin resonance are found below $$T_c$$ = 35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper-pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high-$$T_c$$ superconducting families share a common nature.

論文

Quantitative characterization of the nanoscale local lattice strain induced by Sr dopants in La$$_{1.92}$$Sr$$_{0.08}$$CuO$$_{4}$$

Lin, J. Q.*; Liu, X.*; Blackburn, E.*; 脇本 秀一; Ding, H.*; Islam, Z.*; Sinha, S. K.*

Physical Review Letters, 120(19), p.197001_1 - 197001_6, 2018/05

https://doi.org/10.1103/PhysRevLett.120.197001
 パーセンタイル：100(Physics, Multidisciplinary)

X線散漫散乱の観測により、銅酸化物高温超伝導体La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$中の不純物Srにより生じるナノスケールの格子歪みを観測した。この結果は、これまで議論となっていた不純物による歪みの性質を明らかにしたとともに、STMで観測されているギャップの不均一性の原因ではないことを明らかにした。

論文

First direct mass measurements of nuclides around $$Z$$ = 100 with a multireflection time-of-flight mass spectrograph

伊藤 由太*; Schury, P.*; 和田 道治*; 新井 郁也*; 羽場 宏光*; 平山 賀一*; 石澤 倫*; 加治 大哉*; 木村 創大*; 小浦 寛之; et al.

Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04

https://doi.org/10.1103/PhysRevLett.120.152501
 被引用回数：11 パーセンタイル：3.78(Physics, Multidisciplinary)

冷たい核融合反応および熱い融合反応によって生成した変形閉殻中性子数152の近傍に位置する原子核$$^{246}$$Es, $$^{251}$$Fm、および超フェルミウム原子核$$^{249-252}$$Md, $$^{254}$$Noの質量の直接測定を、多反射時間飛行質量分析装置(MR-TOF)を用いて実施した。$$^{246}$$Esおよび$$^{249,250,252}$$Mdの質量測定は世界で初めての成果である。さらに$$^{249,250}$$Mdの質量を$$alpha$$崩壊連鎖のアンカーポイントとして用いて$$^{261}$$Bhおよび$$^{266}$$Mtまでの重い原子核の質量を決定した。これらの新測定された質量を理論質量計算と比較し、巨視的・微視的模型の予測値と良い一致が見られることを示した。近接する3つの質量値から求められる経験的殻ギャップエネルギー$$delta_{2n}$$を今回の質量値から求め、MdおよびLrに対する変形閉殻中性子数$$N=152$$の存在を裏付ける結果を得た。

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