高橋 佳之*; 小泉 光生
日本原子力学会誌, 62(8), p.452 - 456, 2020/08
本稿は、日本原子力学会誌の連載口座「核セキュリティ入門」に「核セキュリティのための核検知技術」という題名で、不法な核物質移転を検知するための技術開発について解説した記事の1章として寄稿するものである。解説記事では、原子力機構が文部科学省「核セキュリティ強化等推進事業費補助金」の一環として進めている技術開発のうち、レーザー・コンプトン散乱ガンマ線をプローブとした原子核共鳴蛍光散乱(Nuclear Resonance Fluorescence: NRF)による核検知・測定技術開発を紹介した。このNRF技術は、核種特有のガンマ線吸収・放出を用いるため、核種を選択的に測定することができる。また、高エネルギーのガンマ線を使用するので貫通力が高く、粒子放出の閾値以下のガンマ線エネルギーを使用するので、照射による放射化がほとんどないという点に特徴がある。この技術を用いた遮蔽物中に隠ぺいされている核物質を検知する技術を提案し、その実証実験を進めている。
田屋 英俊*; Park, A.*; Cho, S.*; Gubler, P.; 服部 恒一*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; 門内 明彦*; 大西 明*; et al.
Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08
We investigate the hadron production from the vortical quark-gluon plasma created in heavy-ion collisions. Based on the quark-coalescence and statistical hadronization models, we show that total hadron yields summed over the spin components are enhanced by the local vorticity with quadratic dependence. The enhancement factor amounts to be a few percent and may be detectable within current experimental sensitivities. We also show that the effect is stronger for hadrons with larger spin, and thus propose a new signature of the local vorticity, which may be detected by the yield ratio of distinct hadron species having different spins such as and . The vorticity dependence of hadron yields seems robust, with consistent predictions in both of the hadron production mechanisms for reasonable values of the vorticity strength estimated for heavy-ion collisions.
Ku, Y.*; 谷田 聖; Belle Collaboration*; 他153名*
Physical Review D, 102(1), p.012003_1 - 012003_9, 2020/07
We report searches for and decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a data sample that contains pairs and was collected near the resonance with the Belle detector at the KEKB collider. We observe no significant signal for either decay and set upper limits on their branching fractions at confidence level of and .
Chen, Y. Q.*; 谷田 聖; Belle Collaboration*; 他181名*
Physical Review D, 102(1), p.012002_1 - 012002_12, 2020/07
We present the results of the first Dalitz plot analysis of the decay . The analysis is performed on a data set corresponding to an integrated luminosity of 953 collected by the Belle detector at the asymmetric-energy KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels , , , , and , together with and S-wave components. The decays and are observed for the first time. We measure ratio of the branching fractions, . Using the Dalitz fit result, the ratio is measured to be ; this is much lower than the theoretical expectations () made under the assumption that is a pure state. The product branching fraction is determined. In addition, the contribution to the resonance shape is confirmed with 10.1 statistical significance using the three-channel Flatte model. We also measure . This is consistent with, and more precise than, the current world average , deviates with a significance of more than from the theoretical predictions of (0.51-0.92)%.
Chilikin, K.*; 谷田 聖; Belle Collaboration*; 他194名*
Journal of High Energy Physics (Internet), 2020(5), p.34_1 - 34_22, 2020/05
The first dedicated search for the is carried out using the decays , , , and with . No significant signal is found. For the mass range between and , the branching-fraction upper limits are determined to be , , , and at 90% C. L. The analysis is based on the 711 data sample collected on the resonance by the Belle detector, which operated at the KEKB asymmetric-energy collider.
阿部 伸行*; 塩澤 俊介*; 松浦 慧介*; 佐賀山 基*; 中尾 朗子*; 大原 高志; 徳永 祐介*; 有馬 孝尚*
Physical Review B, 101(18), p.180407_1 - 180407_5, 2020/05
The correlation between magnetism and electric polarization in a chiral insulating magnet BaFeOCl has been investigated. The temperature dependence of magnetic susceptibility shows an anomaly at 564 K, suggesting the onset of antiferromagnetic order of Fe moments. Electric polarization appears in a magnetic field below TN due to the spin-direction-dependent metal-ligand hybridization. The direction of the electric polarization can be controlled in three-dimensional space by changing the direction of an external magnetic field. This compound also shows an antiferromagnetic-to-weak-ferromagnetic transition accompanied by a structural phase transition at 140 K.
Seidl, R.*; 谷田 聖; Belle Collaboration*; 他136名*
Physical Review D, 101(9), p.092004_1 - 092004_13, 2020/05
We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a 558 fb data sample collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他175名*
Physical Review D, 101(9), p.091101_1 - 091101_8, 2020/05
We report the measurement of via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb collected with the Belle detector at the and nearby. We find evidence for an enhancement with a 3.4 significance in the invariant mass of The measured mass and width are and , respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/ recently reported by Belle in The product of the cross section and the branching fraction of is measured from threshold to 5.6 GeV.
足立 一郎*; 谷田 聖; Belle II Collaboration*; 他358名*
Physical Review Letters, 124(14), p.141801_1 - 141801_9, 2020/04
Theories beyond the standard model often predict the existence of an additional neutral boson, the . Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a in the process and of a lepton-flavor-violating in . We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an theory, into upper limits on the coupling constant at the level of - for GeV/.
Caria, G.*; 谷田 聖; Belle Collaboration*; 他202名*
Physical Review Letters, 124(16), p.161803_1 - 161803_8, 2020/04
The experimental results on the ratios of branching fractions and , where denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of and , based on a data sample containing events recorded at the resonance with the Belle detector at the KEKB collider. In this analysis the tag-side meson is reconstructed in a semileptonic decay mode and the signal-side is reconstructed in a purely leptonic decay. The measured values are and , where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within , and standard deviations for , and their combination, respectively. This work constitutes the most precise measurements of and performed to date as well as the first result for based on a semileptonic tagging method.
JAEA-Review 2019-040, 77 Pages, 2020/03
中里 晟也*; 岩佐 和晃*; 橋本 大輔*; 塩澤 真未*; 桑原 慶太郎*; 中尾 裕則*; 佐賀山 基*; 石角 元志*; 大原 高志; 中尾 朗子*; et al.
JPS Conference Proceedings (Internet), 30, p.011128_1 - 011128_6, 2020/03
Successive phase transitions of IrSn (: La and Ce) were studied using neutron and X-ray diffraction techniques. A semimetal CeIrSn undergoes three phase transitions: an antiferromagnetic ordering characterized by a propagation vector = (1/2, 1/2, 2/5) below 0.6 K, a structural transformation with = (1/4, 1/4, 1/4) at 2.0 K, and another structural transformation with = (1/2, 1/2, 0) above room temperature. LaIrSn was confirmed to be a superconductor below 2.5 K under the = (1/2, 1/2, 0) structure that also appears above room temperature.
Chu, K.*; 谷田 聖; Belle Collaboration*; 他176名*
Physical Review D, 101(5), p.052012_1 - 052012_8, 2020/03
Using a data sample of BB pairs collected on the resonance with the Belle detector at the KEKB asymmetric-energy collider, we report the observations of and . We measure a decay branching fraction of in for with a significance of 5.5 standard deviations. The contribution from is excluded. We measure a decay branching fraction of for with with a significance of 5.4 standard deviations. We study the difference of the distributions in and .
Katrenko, P.*; 谷田 聖; Belle Collaboration*; 他168名*
Physical Review Letters, 124(12), p.122001_1 - 122001_7, 2020/03
We report the first observation of the radiative decay of the into a charmonium state. The statistical significance of the observed signal of is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br() = . We also searched for radiative decays into and and set upper limits on their branching fractions. These results are obtained from a 24.9 fb data sample collected with the Belle detector at the KEKB asymmetric-energy collider at a center-of-mass energy equal to the mass using tagging by the transitions.
Abudinn, F.*; 谷田 聖; Belle II Collaboration*; 他420名*
Chinese Physics C, 44(2), p.021001_1 - 021001_12, 2020/02
From April to July 2018, a data sample at the peak energy of the resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be () pb, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.
Kou, E.*; 谷田 聖; Belle II Collaboration*; 他537名*
Progress of Theoretical and Experimental Physics (Internet), 2020(2), p.029201_1 - 029201_6, 2020/02
In the original version of this manuscript, an error was introduced on pp.352. "2.7nb:1.6nb" has been corrected to "2.4nb:1.3nb" in the current online and printed version.
Li, Y.*; 谷田 聖; Belle Collaboration*; 他175名*
Physical Review D, 100(11), p.112010_1 - 112010_8, 2019/12
Using the data sample of 711 fb of on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays , , and . The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against baryons in selected candidates. The branching fraction of is measured to be , where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on and are determined to be and , respectively.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他172名*
Physical Review D, 100(11), p.111103_1 - 111103_8, 2019/12
Using a data sample of 921.9 fb collected with the Belle detector, we study the process of via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to with a significance of 5.9, including the systematic uncertainties. The measured mass and width are and , respectively. The product of the cross section and the branching fraction of is measured from the threshold to 5.59 GeV.
Kou, E.*; 谷田 聖; Belle II Collaboration*; 他537名*
Progress of Theoretical and Experimental Physics (Internet), 2019(12), p.123C01_1 - 123C01_654, 2019/12
We present the physics program of the Belle II experiment, located on the intensity frontier SuperKEKB collider. Belle II collected its first collisions in 2018, and is expected to operate for the next decade. It is anticipated to collect 50/ab of collision data over its lifetime. This book is the outcome of a joint effort of Belle II collaborators and theorists through the Belle II theory interface platform (B2TiP), an effort that commenced in 2014. The aim of B2TiP was to elucidate the potential impacts of the Belle II program, which includes a wide scope of physics topics: B physics, charm, tau, quarkonium, electroweak precision measurements and dark sector searches. It is composed of nine working groups (WGs), which are coordinated by teams of theorist and experimentalists conveners: Semileptonic and leptonic B decays, Radiative and Electroweak penguins, and (time-dependent CP violation) measurements, measurements, Charmless hadronic B decay, Charm, Quarkonium(-like), tau and low-multiplicity processes, new physics and global fit analyses. This book highlights "golden- and silver-channels", i.e. those that would have the highest potential impact in the field. Theorists scrutinised the role of those measurements and estimated the respective theoretical uncertainties, achievable now as well as prospects for the future. Experimentalists investigated the expected improvements with the large dataset expected from Belle II, taking into account improved performance from the upgraded detector.
Li, H.*; 谷田 聖; Belle Collaboration*; 他131名*
Physical Review D, 100(9), p.092008_1 - 092008_26, 2019/11
This work reports the first observation of azimuthal asymmetries around the thrust axis in annihilation of pairs of back-to-back charged pions in one hemisphere, and and mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The and asymmetries rise with the relative momentum of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the final states will provide additional information on the flavor structure of . This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.