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論文

Hard X-ray photoemission study of bulk single-crystalline InGaZnO$$_4$$

芝田 悟朗; 他9名*

Applied Physics Letters, 126(24), p.241902_1 - 241902_6, 2025/06

https://doi.org/10.1063/5.0271655
 被引用回数：0

We performed hard X-ray photoemission spectroscopy (HAXPES) experiments of bulk single-crystalline InGaZnO$$_4$$ (sc-IGZO), which was recently synthesized via the optical floating zone method, in order to reveal the bulk intrinsic electronic structure. We find that oxygen vacancies are preferentially located around In atoms in as-grown crystals, which are filled out by post-annealing in an oxygen atmosphere. The subgap states near the valence-band maximum (VBM) were much weaker than those in the previous study even without oxygen annealing, which suggests that the loss of crystallinity is relevant to the formation of them in addition to the oxygen vacancies.

論文

Spin-orbit-entangled state of Ba$$_2$$CaOsO$$_6$$ studied by O $$K$$-edge resonant inelastic X-ray scattering and Raman spectroscopy

岡本 淳*; 芝田 悟朗; 藤森 淳; 他9名*

npj Quantum Materials (Internet), 10, p.44_1 - 44_8, 2025/04

https://doi.org/10.1038/s41535-025-00757-4
 被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Transition-metal ions with 5$$d^2$$ electronic configuration in a cubic crystal field are prone to have a vanishing dipolar magnetic moment but finite higher-order multipolar moments, and they are expected to exhibit exotic physical properties. Through an investigation using resonant inelastic X-ray spectroscopy (RIXS), Raman spectroscopy, and theoretical ligand-field multiplet and ab initio calculations, we fully characterized the electronic structure of Ba$$_2$$CaOsO$$_6$$, particularly, the crystal field symmetry of the 5$$d^2$$ electrons in this anomalous material. The low-energy multiplet excitations from RIXS at the oxygen $$K$$ edge and Raman-active phonons both show no splitting, confirming the absence of Jahn-Teller distortion. These findings are consistent with the ground state with the "hidden order" of magnetic octupoles.

論文

Characteristic deformation microstructure evolution and deformation mechanisms in face-centered cubic high/medium entropy alloys

吉田 周平*; Gong, W.; 他9名*

Acta Materialia, 283, p.120498_1 - 120498_15, 2025/01

https://doi.org/10.1016/j.actamat.2024.120498
 被引用回数：3 パーセンタイル：57.76(Materials Science, Multidisciplinary)

Face-centered cubic (FCC) high/medium entropy alloys (HEAs/MEAs), novel multi-principal element alloys, are known to exhibit exceptional mechanical properties at room temperature; however, the origin is still elusive. Here, we report the deformation microstructure evolutions in a tensile-deformed Co$$_{20}$$Cr$$_{40}$$Ni$$_{40}$$ representative MEA and Co$$_{60}$$Ni$$_{40}$$ alloy, a conventional binary alloy for comparison. These FCC alloys have high/low friction stresses, and share similar other material properties. The Co$$_{20}$$Cr$$_{40}$$Ni$$_{40}$$ MEA exhibited higher yield strength and work-hardening ability than in the Co$$_{60}$$Ni$$_{40}$$ alloy. Deformation microstructures in the Co$$_{20}$$Cr$$_{40}$$Ni$$_{40}$$ alloy were marked by the presence of coarse dislocation cells (DCs) regardless of grain orientation and a few deformation twins (DTs) in grains with the tensile axis (TA) near $$<$$1 1 1$$>$$. In contrast, the MEA developed three distinct deformation microstructures depending on grain orientations: fine DCs in grains with the TA near $$<$$1 0 0$$>$$, planar dislocation structure (PDS) in grains with other orientations, and a high density of DTs along with PDS in grains oriented $$<$$1 1 1$$>$$. These findings demonstrate that FCC HEAs/MEAs with high friction stresses naturally develop unique deformation microstructures which is beneficial for realizing superior mechanical properties compared to conventional materials.

論文

Production cross-sections of residual nuclides from $$^{93}$$Zr + $$p$$ at 27 MeV/nucleon

Hwang, J.*; Chillery, T.*; 堂園 昌伯*; 今井 伸明*; 道正 新一郎*; 炭竃 聡之*; 千賀 信幸*; 大田 晋輔*; 中山 梓介; 他49名*

Progress of Theoretical and Experimental Physics (Internet), 2024(9), p.093D03_1 - 093D03_12, 2024/09

https://doi.org/10.1093/ptep/ptae139
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

核変換は高レベル廃棄物の再処理、特に使用済み燃料から$$^{93}$$Zrのような長寿命核種を処理するための有望な手段であると考えられている。これらの核種に対する核反応データを蓄積することは、核変換の検討や反応機構を包括的に理解するために不可欠である。本研究では、$$^{93}$$Zrに対する陽子入射反応からの残留核生成断面積を、核子当たり27MeVのエネルギーで逆運動学法を用いて測定した。理研RIBFのOEDOビームラインを用いて、$$^{91-93}$$Nb, $$^{91,92}$$Zr, $$^{88,89}$$Yの各同位体の生成断面積を導出した。励起関数について、TALYSやCCONEによる理論予測は、本研究や先行研究の実験値と概ね良い一致を示した。本研究で測定された断面積は、廃棄物処理に関する将来の検討のための貴重なデータとなる。

論文

Detailed structure of $$^{131}$$Sn populated in the $$beta$$ decay of isomerically purified $$^{131}$$In states

Benito, J.*; Andreyev, A. N.; 他93名*

Physical Review C, 110(1), p.014328_1 - 014328_19, 2024/07

https://doi.org/10.1103/PhysRevC.110.014328
 被引用回数：4 パーセンタイル：74.11(Physics, Nuclear)

The excited structure of the single-hole nucleus 131Sn populated by the $$beta$$-decay of $$^{131}$$In was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited $$nu h_{11/2}$$ neutron-hole state was confirmed.

論文

Compound-nucleus and doorway-state decays of $$beta$$-delayed neutron emitters $$^{51,52.53}$$K

Xu, Z. Y.*; Grzywacz, R.*; Andreyev, A. N.; 他49名*

Physical Review Letters, 133(4), p.042501_1 - 042501_7, 2024/07

https://doi.org/10.1103/PhysRevLett.133.042501
 被引用回数：2 パーセンタイル：43.84(Physics, Multidisciplinary)

We investigated decays of $$^{51,52,53}$$K at the ISOLDE Decay Station at CERN in order to understand the mechanism of the $$beta$$-delayed neutron-emission ($$beta$$n) process. The experiment quantified neutron and $$gamma$$-ray emission paths for each precursor. We used this information to test the hypothesis, first formulated by Bohr in 1939, that neutrons in the $$beta$$n process originate from the structureless "compound nucleus". The data are consistent with this postulate for most of the observed decay paths. The agreement, however, is surprising because the compound-nucleus stage should not be achieved in the studied $$beta$$ decay due to insufficient excitation energy and level densities in the neutron emitter. In the $$^{53}$$K $$beta$$n decay, we found a preferential population of the first excited state in $$^{52}$$Ca that contradicted Bohr's hypothesis. The latter was interpreted as evidence for direct neutron emission sensitive to the structure of the neutron-unbound state. We propose that the observed nonstatistical neutron emission proceeds through the coupling with nearby doorway states that have large neutron-emission probabilities. The appearance of "compound-nucleus" decay is caused by the aggregated small contributions of multiple doorway states at higher excitation energy.

論文

Understanding spin currents from magnon dispersion and polarization; Spin-Seebeck effect and neutron scattering study on Tb$$_3$$Fe$$_5$$O$$_{12}$$

川本 陽*; 吉川 貴史; 齊藤 英治; 他9名*

Applied Physics Letters, 124(13), p.132406_1 - 132406_7, 2024/03

https://doi.org/10.1063/5.0197831
 被引用回数：4 パーセンタイル：78.60(Physics, Applied)

Magnon spin currents in the ferrimagnetic garnet Tb$$_{3}$$Fe$$_{5}$$O$$_{12}$$ with 4$$f$$ electrons were examined through the spin-Seebeck effect and neutron scattering measurements. The compound shows a magnetic compensation, where the spin-Seebeck signal reverses above and below $$T$$$$_{rm comp}$$ = 249.5(4) K. Unpolarized neutron scattering unveils two major magnon branches with finite energy gaps, which are well explained in the framework of spin-wave theory. Their temperature dependencies and the direction of the precession motion of magnetic moments, i.e., magnon polarization, defined using polarized neutrons, explain the reversal at $$T$$$$_{rm comp}$$ and decay of the spin-Seebeck signals at low temperatures. We illustrate an example that momentum- and energy-resolved microscopic information is a prerequisite to understand the magnon spin current.

論文

Revealing the role of high-valence elementary substitution in the hydrogen-induced Mottronic transitions of vanadium dioxide

Zhou, X.*; 福谷 克之; 他9名*

Applied Physics Letters, 124(8), p.082103_1 - 082103_7, 2024/02

https://doi.org/10.1063/5.0189271
 被引用回数：6 パーセンタイル：87.23(Physics, Applied)

Electron-doping Mottronics within correlated vanadium dioxide opens up a paradigm to abruptly regulate the Mottronic phase transitions via adjusting the $$d$$-orbital occupancy and configuration. Nevertheless, the potential impact of high-valence elementary substitution in the hydrogen-associated Mottronic transitions of VO$$_{2}$$ is yet unclear. Herein, we demonstrate the role of high-valence elementary substitution in regulating the hydrogen-triggered Mottronic transitions of VO$$_{2}$$, assisted by quantitative hydrogen analysis using the nuclear reaction analysis. Substituting vanadium with a high-valence transitional metal within doped-VO$$_{2}$$ largely reduces the hydrogen incorporation compared to the intrinsic VO$$_{2}$$ under the low temperature hydrogenation process. Therefore, in contrast to hydrogen-induced electron localization of intrinsic VO$$_{2}$$ upon low-temperature hydrogenation, only the hydrogen-triggered metallic state is observed within the hydrogen-associated phase diagram of W$$_{x}$$V$$_{1-x}$$O$$_{2}$$, as further probed by the near-edge X-ray absorption fine structure analysis and X-ray photoelectron spectroscopy. The present work reveals the overlooked role associated with the donor substitutions that largely influences the competitive equilibrium between the two rival hydrogen-induced Mottronic transitions within VO$$_{2}$$ toward either the metallic or the highly insulating phase.

論文

Local atomic structures and lattice dynamics of inverse colossal barocaloric ammonium thiocyanate

Zhang, Z.*; Gong, W.; 川北 至信; 他9名*

Physical Review Materials (Internet), 7(12), p.125402_1 - 125402_9, 2023/12

https://doi.org/10.1103/PhysRevMaterials.7.125402
 被引用回数：2 パーセンタイル：20.33(Materials Science, Multidisciplinary)

NH$$_{4}$$SCN exhibits successive phase transitions from monoclinic to orthorhombic, and then to tetragonal. The former phase transition is accompanied by an inverse colossal barocaloric effect and a huge negative thermal expansion. This transition is complicated by the possibly coexisting orientational disorder of NH$$_{4}$$$$^{+}$$ and SCN$$^{-}$$, and the mechanism is still unclear. Here, NH$$_{4}$$SCN is investigated using high-resolution neutron powder diffraction, pair distribution function analysis, and Raman scattering. Both the average and local structural analysis indicate that only NH$$_{4}$$$$^{+}$$ is orientationally disordered in the orthorhombic phase and SCN$$^{-}$$ becomes subsequently disordered in the tetragonal phase. Both temperature-induced and pressure-induced hardening behaviors of SCN$$^{-}$$ related vibrations are observed, which leads to the breakage of hydrogen bonds-linked NH$$_{4}$$$$^{+}$$ with SCN$$^{-}$$ and further facilitates phase transition. Our findings provide a solid standing point of atomic structures and dynamics, on which the scenario of the phase transition and the associated physical properties is established.

論文

Studying the impact of deuteron non-elastic breakup on $$^{93}$$Zr + d reaction cross sections measured at 28 MeV/nucleon

Chillery, T.*; Hwang, J.*; 堂園 昌伯*; 今井 伸明*; 道正 新一郎*; 炭竃 聡之*; 千賀 信幸*; 大田 晋輔*; 中山 梓介; 他49名*

Progress of Theoretical and Experimental Physics (Internet), 2023(12), p.121D01_1 - 121D01_11, 2023/12

https://doi.org/10.1093/ptep/ptad139
 被引用回数：4 パーセンタイル：59.55(Physics, Multidisciplinary)

重陽子は弱束縛系でありクーロン力と核力の下で容易に陽子と中性子に分解する。これまでの実験からは、核子当たり50から200MeVといった高入射エネルギーではこの分解過程が残留核生成に大きな影響を与えることが示されている。しかし、核子当たり50MeV以下のエネルギーでの断面積データはまだ不足している。本研究では、BigRIPSセパレータ、OEDOビームライン、SHARAQスぺクトロメータを用いて、$$^{93}$$Zr+d反応断面積を核子当たり約28MeVにおいて逆運動学法を用いて測定した。本研究で得られた断面積を過去の測定結果や理論計算と比較した。重陽子の分解の効果を定量的に考慮したDEURACS計算により実験データがよく再現された。本研究で測定された低エネルギー領域におけるデータは、将来の核廃棄物処理施設の検討に役立つと考えられる。

論文

Deformation versus sphericity in the ground states of the lightest gold isotopes

Cubiss, J. G.*; Andreyev, A. N.; 他49名*

Physical Review Letters, 131(20), p.202501_1 - 202501_8, 2023/11

https://doi.org/10.1103/PhysRevLett.131.202501
 被引用回数：10 パーセンタイル：79.13(Physics, Multidisciplinary)

The changes in mean-squared charge radii of neutron-deficient gold nuclei have been determined using the in-source, resonance-ionization laser spectroscopy technique, at the ISOLDE facility (CERN). From these new data, nuclear deformations are inferred, revealing a competition between deformed and spherical configurations. The isotopes $$^{180,181,182}$$Au are observed to possess well-deformed ground states and, when moving to lighter masses, a sudden transition to near-spherical shapes is seen in the extremely neutron deficient nuclides, $$^{176,177,179}$$Au. A case of shape coexistence and shape staggering is identified in $$^{178}$$Au which has a ground and isomeric state with different deformations. These new data reveal a pattern in ground-state deformation unique to the gold isotopes, whereby, when moving from the heavy to light masses, a plateau of well-deformed isotopes exists around the neutron midshell, flanked by near-spherical shapes in the heavier and lighter isotopes-a trend hitherto unseen elsewhere in the nuclear chart. The experimental charge radii are compared to those from Hartree-Fock-Bogoliubov calculations using the D1M Gogny interaction and configuration mixing between states of different deformation. The calculations are constrained by the known spins, parities, and magnetic moments of the ground states in gold nuclei and show a good agreement with the experimental results.

論文

Observation of a threshold cusp at the $$Lambdaeta$$ threshold in the $$pK^-$$ mass spectrum with $$Lambda_c^+ to pK^-pi^+$$ decays

Yang, S.*; 谷田 聖; Belle Collaboration*; 他196名*

Physical Review D, 108(3), p.L031104_1 - L031104_6, 2023/08

https://doi.org/10.1103/PhysRevD.108.L031104
 被引用回数：5 パーセンタイル：57.15(Astronomy & Astrophysics)

We observe a narrow peaking structure in the $$pK^{-}$$ invariant-mass spectrum near the $$Lambdaeta$$ threshold. The peak is clearly seen in 1.5 million events of $$Lambda_{c}^{+} rightarrow p K^{-} pi^{+}$$ decay using the $$980~{rm fb^{-1}}$$ data sample collected by the Belle detector at the KEKB asymmetric-energy $$e^{+}e^{-}$$ collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the $$Lambdaeta$$ threshold. The best fit is obtained with a coherent sum of a Flatt$$rm{acute{e}}$$ function and a constant background amplitude with the $$chi^2/{rm n.d.f}=257/243$$ ($$p = 0.25$$), while the fits to Breit-Wigner functions are unfavored by more than 7$$sigma$$. The best fit explains the structure as a cusp at the $$Lambdaeta$$ threshold, and the obtained parameters are consistent with the known properties of $$Lambda(1670)$$. The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.

論文

Measurement of the $$^{14}$$N(n, p)$$^{14}$$C cross section at the CERN n_TOF facility from subthermal energy to 800 keV

Torres-S$'a$nchez, P.*; 原田 秀郎; 木村 敦; 他129名*

Physical Review C, 107(6), p.064617_1 - 064617_15, 2023/06

https://doi.org/10.1103/PhysRevC.107.064617
 被引用回数：1 パーセンタイル：25.07(Physics, Nuclear)

The $$^{14}$$N(n, p)$$^{14}$$C reaction cross section has been measured at the CERN neutron time-of-flight facility n_TOF from subthermal energy to 800 keV. The experiment was performed at the experimental area EAR-2 with a stack of micromesh gaseous structure detectors (MicroMegas). $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li and $$^{235}$$U(n, f) reactions were used as references. A thermal cross section was obtained (1.809 $$pm$$ 0.045 b) that is lower than the two most recent measurements by slightly more than one standard deviation, but in line with the ENDF/B-VIII.0 andJEFF-3.3 evaluations.

論文

First spectroscopic study of odd-odd $$^{78}$$Cu

Pedersen, L. G.*; Sahin, E.*; G$"o$rgen, 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

https://doi.org/10.1103/PhysRevC.107.044301
 被引用回数：3 パーセンタイル：57.48(Physics, Nuclear)

Nuclei in the vicinity of $$^{78}$$Ni ($$Z$$=28, $$N$$=50) are important benchmarks to study the evolution of shell structure far from stability. Excited states in $$^{78}$$Cu were observed for the first time following the $$beta$$-decay of $$^{78}$$Ni, which was produced by in-flight fission of $$^{238}$$U. Using $$gamma$$-ray coincidences, a level scheme comprising eight excited states was built. Using the observed $$beta$$ feeding and the $$gamma$$-decay properties of the excited states, spin was tentatively assigned to 5 new states. In addition to the $$gamma$$-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 $$^{78}$$Ni core was obtained.

論文

Search for $$X(3872)topi^+pi^-pi^0$$ at Belle

Yin, J. H.*; 谷田 聖; Belle Collaboration*; 他193名*

Physical Review D, 107(5), p.052004_1 - 052004_8, 2023/03

https://doi.org/10.1103/PhysRevD.107.052004
 被引用回数：3 パーセンタイル：40.72(Astronomy & Astrophysics)

We present a search for the decay $$X(3872) to pi^+pi^-pi^0$$ in the $$(772pm11)times10^6$$ $$Upsilon(4S)to B bar B$$ data sample collected at the Belle detector, where the $$X(3872)$$ is produced in $$B^{pm}to K^{pm}X(3872)$$ and $$B^{0}to K_{S}^0 X(3872)$$ decays. We do not observe a signal, and set 90% credible upper limits for two different models of the decay processes: if the decay products are distributed uniformly in phase space, $$mathcal{B}(X(3872) to pi^+pi^-pi^0) < 1.3%$$; if $$M(pi^+pi^-)$$ is concentrated near the mass of the $$D^0 bar D^0$$ pair in the process $$X(3872)to D^0bar{D}^{*0}+c.c.to D^0 bar D^{0}pi^0topi^+ pi^- pi^0$$, $$mathcal{B}(X(3872) to pi^+pi^-pi^0) < 1.2times10^{-3}$$.

論文

Measurement of the $$B^+/B^0$$ production ratio in $$e^+e^-$$ collisions at the $$Upsilon(4S)$$ resonance using $$B rightarrow J/psi(ellell) K$$ decays at Belle

Choudhury, S.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 107(3), p.L031102_1 - L031102_6, 2023/02

https://doi.org/10.1103/PhysRevD.107.L031102
 被引用回数：12 パーセンタイル：72.68(Astronomy & Astrophysics)

We measure the ratio of branching fractions for the $$Upsilon (4S)$$ decays to $$B^+B^-$$ and $$B^0bar{B}{}^0$$ using $$B^+ rightarrow J/psi(ellell) K^+$$ and $$B^0 rightarrow J/psi(ellell) K^0$$ samples, where $$J/psi(ellell)$$ stands for $$J/psi to ell^+ell^-$$ ($$ell = e$$ or $$mu$$), with $$711$$ fb$$^{-1}$$ of data collected at the $$Upsilon(4S)$$ resonance with the Belle detector. We find the decay rate ratio of $$Upsilon(4S) rightarrow B^+B^-$$ over $$Upsilon(4S) rightarrow B^0bar{B}{}^0$$ to be $$1.065pm0.012pm 0.019 pm 0.047$$, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in $$B to J/psi(ellell) K$$.

論文

Measurement of the branching fractions for Cabibbo-suppressed decays $$D^{+}to K^{+} K^{-}pi^{+}pi^{0}$$ and $$D_{(s)}^{+}to K^{+}pi^{-}pi^{+}pi^{0}$$ at Belle

Li, L. K.*; 谷田 聖; Belle Collaboration*; 他197名*

Physical Review D, 107(3), p.033003_1 - 033003_9, 2023/02

https://doi.org/10.1103/PhysRevD.107.033003
 被引用回数：0 パーセンタイル：0.00(Astronomy & Astrophysics)

We present measurements of the branching fractions for the singly Cabibbo-suppressed decays $$D^+to K^{+}K^{-}pi^{+}pi^{0}$$ and $$D_s^{+}to K^{+}pi^{-}pi^{+}pi^{0}$$, and the doubly Cabibbo-suppressed decay $$D^{+}to K^{+}pi^{-}pi^{+}pi^{0}$$, based on 980 $${rm fb}^{-1}$$ of data recorded by the Belle experiment at the KEKB $$e^{+}e^{-}$$ collider. We measure these modes relative to the Cabibbo-favored modes $$D^{+}to K^{-}pi^{+}pi^{+}pi^{0}$$ and $$D_s^{+}to K^{+}K^{-}pi^{+}pi^{0}$$. Our results for the ratios of branching fractions are $$B(D^{+}to K^{+}K^{-}pi^{+}pi^{0})/B(D^{+}to K^{-}pi^{+}pi^{+}pi^{0}) = (11.32 pm 0.13 pm 0.26)%$$, $$B(D^{+}to K^{+}pi^{-}pi^{+}pi^{0})/B(D^{+}to K^{-}pi^{+}pi^{+}pi^{0}) = (1.68 pm 0.11pm 0.03)%$$, and $$B(D_s^{+}to K^{+}pi^{-}pi^{+}pi^{0})/B(D_s^{+}to K^{+}K^{-}pi^{+}pi^{0}) = (17.13 pm 0.62 pm 0.51)%$$, where the uncertainties are statistical and systematic, respectively. The second value corresponds to $$(5.83pm 0.42)timestan^4theta_C$$, where $$theta_C$$ is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $$B(D^{+}to K^{-}pi^{+}pi^{+}pi^{0})$$ and $$B(D_s^{+}to K^{+}K^{-}pi^{+}pi^{0})$$ yields $$B(D^{+}to K^{+}K^{-}pi^{+}pi^{0})= (7.08pm 0.08pm 0.16pm 0.20)times10^{-3}$$, $$B(D^{+}to K^{+}pi^{-}pi^{+}pi^{0})= (1.05pm 0.07pm 0.02pm 0.03)times10^{-3}$$, and $$B(D_s^{+}to K^{+}pi^{-}pi^{+}pi^{0}) = (9.44pm 0.34pm 0.28pm 0.32)times10^{-3}$$, where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.

論文

Formation and evolution of carbonaceous asteroid Ryugu; Direct evidence from returned samples

中村 智樹*; 大澤 崇人; 他219名*

Science, 379(6634), p.eabn8671_1 - eabn8671_14, 2023/02

https://doi.org/10.1126/science.abn8671
 被引用回数：223 パーセンタイル：99.98(Multidisciplinary Sciences)

1から8mmのリュウグウ粒子16個の鉱物学的,岩石学的、および物理的特性は、それらがCIコンドライトに最も類似していることを示している。磁硫鉄鉱中のCO$$_{2}$$含有水の存在は、母天体が太陽系星雲のH$$_{2}$$OおよびCO$$_{2}$$のスノーラインを越えた領域で形成したことを示しており、ここでは、リュウグウの鉱物学に基づくと、小さなコンドリュールやCa, Alを含む非常に限られた量の高温物質がある。流体-岩石反応は、低温,高pH、および水/岩石の質量比が1未満の還元条件で発生し、リュウグウのサンプルで最も変化の少ない断片として残っているかんらん石-輝石に富む岩相を、リュウグウサンプルの主要な岩相であるフィロケイ酸塩-炭酸塩に富むものに変えた。リュウグウの母体の流体から磁鉄鉱が結晶化したとき、原始太陽系星雲はまだ存在していた可能性がある。

論文

Measurements of the branching fractions $$mathcal{B} (bar{B}{}^0 to D^{*+} pi^-)$$ and $$mathcal{B} (bar{B}{}^0 to D^{*+} K^-)$$ and tests of QCD factorization

Krohn, J.-F.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 107(1), p.012003_1 - 012003_12, 2023/01

https://doi.org/10.1103/PhysRevD.107.012003
 被引用回数：3 パーセンタイル：15.61(Astronomy & Astrophysics)

Using $$(771.6 pm 10.6) times 10^6$$ $$Bbar{B}$$ meson pairs recorded by the Belle experiment at the KEKB $$e^+ e^-$$ collider, we report the branching fractions $$mathcal{B}(bar{B}^0 to D^{*+} pi^-) = (2.62 pm 0.02 pm 0.09)times 10^{-3}$$ and $$mathcal{B}(bar{B}^0 to D^{*+} K^-) = (2.22 pm 0.06 pm 0.08)times 10^{-4}$$; the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, $$mathcal{R}_{K/pi}=mathcal{B}(bar{B} to D^{*+}K^-) /mathcal{B}(bar{B} to D^{*+}pi^-) = (8.41 pm 0.24 pm 0.13)times 10^{-2}$$, where systematic uncertainties due to the $$D^{*+}$$ meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for $$bar{B} to D^{*+}h^-$$ and $$bar{B} to D^{*+}ell^-nu$$ decays at squared momentum transfer values equivalent to the mass of the $$h = pi$$ or $$K$$ hadron. The parameters $$|a_1(h)|$$ are measured to be $$|a_1(pi)|= 0.884 pm 0.004 pm 0.003 pm 0.016$$ and $$|a_1(K)|=0.913 pm 0.019 pm 0.008 pm 0.013$$, where the last uncertainties account for all external inputs. These values are approximately $$15%$$ lower than those expected from theoretical predictions. Subsequently, flavor $$SU(3)$$ symmetry is tested by measuring the ratios for pions and kaons, $$|a_1(K)|^2/ |a_1(pi)|^2=1.066 pm 0.042 pm 0.018 pm 0.023$$, as well as for different particle species. The ratio is consistent with unity and therefore no evidence for $$SU(3)$$ symmetry breaking effects is found at the $$5%$$ precision level.

論文

Evidence of a new excited charmed baryon decaying to $$Sigma_{c}(2455)^{0,++} pi^{pm}$$

Li, Y. B.*; 谷田 聖; Belle Collaboration*; 他194名*

Physical Review Letters, 130(3), p.031901_1 - 031901_7, 2023/01

https://doi.org/10.1103/PhysRevLett.130.031901
 被引用回数：16 パーセンタイル：91.49(Physics, Multidisciplinary)

We present the study of $$bar{B}^{0} to Sigma_{c}(2455)^{0,++} pi^{pm} bar{p}$$ decays based on $$772times 10^{6}$$ $$Bbar{B}$$ events collected with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider. The $$Sigma_{c}(2455)^{0,++} $$ candidates are reconstructed via their decay to $$Lambda_{c}^{+} pi^{mp}$$ and $$Lambda_{c}^{+}$$ decays to $$pK^{-}pi^{+},~pK_{S}^{0},$$ and $$Lambdapi^{+}$$ final states. The corresponding branching fractions are measured to be $${cal B}(bar{B}^{0} to Sigma_{c}(2455)^{0} pi^{+} bar{p}) = (1.09 pm 0.06 pm 0.07)times10^{-4}$$ and $${cal B}(bar{B}^{0} to Sigma_{c}(2455)^{++} pi^{-} bar{p}) = (1.84pm 0.11 pm 0.12)times 10^{-4}$$, which are consistent with the world average values with improved precision. A new structure is found in the $$M_{Sigma_{c}(2455)^{0,++}pi^{pm}}$$ spectrum with a significance of $$4.2sigma$$ including systematic uncertainty. The structure is possibly an excited $$Lambda_{c}^{+}$$ and is tentatively named $$Lambda_{c}(2910)^{+}$$. Its mass and width are measured to be $$(2913.8 pm 5.6 pm 3.8)$$ MeV/$$c^{2}$$ and $$(51.8pm20.0 pm 18.8)$$ MeV, respectively. The products of branching fractions for the $$Lambda_{c}(2910)^{+}$$ are measured to be $${cal B}(bar{B}^{0} to Lambda_{c}(2910)^{+}bar{p})times{cal B}(Lambda_{c}(2910)^{+} to Sigma_{c}(2455)^{0}pi^{+}) = (9.5 pm 3.6 pm 1.6)times 10^{-6}$$ and $${cal B}(bar{B}^{0} to Lambda_{c} (2910)^{+}bar{p})times {cal B}(Lambda_{c}(2910)^{+} to Sigma_{c}(2455)^{++}pi^{-}) = (1.24 pm 0.35 pm 0.10)times 10^{-5}$$. Here, the first and second uncertainties are statistical and systematic, respectively.

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