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論文

核セキュリティ入門,3; 核セキュリティのための核物質検知技術

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。

論文

Signatures of the vortical quark-gluon plasma in hadron yields

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

 被引用回数:0 パーセンタイル:100(Physics, Nuclear)

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 $$phi$$ and $$eta'$$. 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.

論文

Search for $$B^0$$ decays to invisible final states ($$+gamma$$) at Belle

Ku, Y.*; 谷田 聖; Belle Collaboration*; 他153名*

Physical Review D, 102(1), p.012003_1 - 012003_9, 2020/07

 被引用回数:0 パーセンタイル:100(Astronomy & Astrophysics)

We report searches for $$B^0torm{invisible}$$ and $$B^0torm{invisible}+gamma$$ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a $$711,{rm fb}^{-1}$$ data sample that contains $$772 times 10^6 Bbar{B}$$ pairs and was collected near the $$Upsilon,(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. We observe no significant signal for either decay and set upper limits on their branching fractions at $$90%$$ confidence level of $$mathcal{B},(B^0torm{invisible}) < 7.8times10^{-5}$$ and $$mathcal{B},(B^0torm{invisible}+gamma) < 1.6times10^{-5}$$.

論文

Dalitz analysis of $$D^{0}to K^{-}pi^{+}eta$$ decays at Belle

Chen, Y. Q.*; 谷田 聖; Belle Collaboration*; 他181名*

Physical Review D, 102(1), p.012002_1 - 012002_12, 2020/07

 被引用回数:0 パーセンタイル:100(Astronomy & Astrophysics)

We present the results of the first Dalitz plot analysis of the decay $$D^{0}to K^{-}pi^{+}eta$$. The analysis is performed on a data set corresponding to an integrated luminosity of 953 $$rm{fb}^{-1}$$ collected by the Belle detector at the asymmetric-energy $$e^{+}e^{-}$$ KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels $$bar{K}^{*}(892)^0eta$$, $$K^{-}a_0(980)^+$$, $$K^{-}a_2(1320)^+$$, $$bar{K}^{*}(1410)^0eta$$, $$K^{*}(1680)^-pi^{+}$$ and $$K_2^{*}(1980)^-pi^{+}$$, together with $$Kpi$$ and $$Keta$$ S-wave components. The decays $$K^{*}(1680)^{-}to K^{-}eta$$ and $$K_{2}^{*}(1980)^{-}to K^{-}eta$$ are observed for the first time. We measure ratio of the branching fractions, $$frac{mathcal{B}(D^{0}to K^{-}pi^{+}eta)}{mathcal{B}(D^{0}to K^{-}pi^{+})}=0.500 pm 0.002 {rm(stat)} pm0.020 {rm(syst)}pm 0.003 {rm (mathcal{B}_{PDG})}$$. Using the Dalitz fit result, the ratio $$frac{mathcal{B}(K^{*}(1680) to K eta)}{mathcal{B}(K^{*}(1680)to Kpi)}$$ is measured to be $$0.11 pm 0.02 {rm(stat)}^{+0.06}_{-0.04}{rm(syst)} pm 0.04{rm(mathcal{B}_{{PDG}})}$$; this is much lower than the theoretical expectations ($$approx 1$$) made under the assumption that $$K^{*}(1680)$$ is a pure $$1^{3}D_1$$ state. The product branching fraction $$mathcal{B}(D^0 to [K_2^{*}(1980)^- to K^{-} eta] pi^{+}) = (2.2^{+1.7}_{-1.9})times10^{-4}$$ is determined. In addition, the $$pieta^{prime}$$ contribution to the $$a_0(980)^{pm}$$ resonance shape is confirmed with 10.1$$sigma$$ statistical significance using the three-channel Flatte model. We also measure $$mathcal{B}(D^0tobar{K}^{*}(892)^0eta)=(1.41^{+0.13}_{-0.12})%$$. This is consistent with, and more precise than, the current world average $$(1.02pm0.30)%$$, deviates with a significance of more than $$3sigma$$ from the theoretical predictions of (0.51-0.92)%.

論文

First search for the $$eta_{c2}(1D)$$ in $$B$$ decays at Belle

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

 被引用回数:0 パーセンタイル:100(Physics, Particles & Fields)

The first dedicated search for the $$eta_{c2}(1D)$$ is carried out using the decays $$B^+ rightarrow eta_{c2}(1D) K^+$$, $$B^0 rightarrow eta_{c2}(1D) K^0_S$$, $$B^0 rightarrow eta_{c2}(1D) pi^- K^+$$, and $$B^+ rightarrow eta_{c2}(1D) pi^+ K^0_S$$ with $$eta_{c2}(1D) to h_c gamma$$. No significant signal is found. For the $$eta_{c2}(1D)$$ mass range between $$3795$$ and $$3845 mathrm{MeV}/c^2$$, the branching-fraction upper limits are determined to be $$mathcal{B}(B^+ rightarrow eta_{c2}(1D) K^+) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 3.7 times 10^{-5}$$, $$mathcal{B}(B^0 rightarrow eta_{c2}(1D) K^0_S) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 3.5 times 10^{-5}$$, $$mathcal{B}(B^0 rightarrow eta_{c2}(1D) pi^- K^+) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 1.0 times 10^{-4}$$, and $$mathcal{B}(B^+ rightarrow eta_{c2}(1D) pi^+ K^0_S) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 1.1 times 10^{-4}$$ at 90% C. L. The analysis is based on the 711 $$mathrm{fb}^{-1}$$ data sample collected on the $$Upsilon(4S)$$ resonance by the Belle detector, which operated at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Magnetically induced electric polarization in Ba$$_{3}$$Fe$$_{2}$$O$$_{5}$$Cl$$_{2}$$ with tunable direction in three dimensions

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

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

The correlation between magnetism and electric polarization in a chiral insulating magnet Ba$$_{3}$$Fe$$_{2}$$O$$_{5}$$Cl$$_{2}$$ has been investigated. The temperature dependence of magnetic susceptibility shows an anomaly at 564 K, suggesting the onset of antiferromagnetic order of Fe$$^{3+}$$ 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.

論文

Update of inclusive cross sections of single and pairs of identified light charged hadrons

Seidl, R.*; 谷田 聖; Belle Collaboration*; 他136名*

Physical Review D, 101(9), p.092004_1 - 092004_13, 2020/05

 被引用回数:0 パーセンタイル:100(Astronomy & Astrophysics)

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$$^{-1}$$ data sample collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Evidence for a vector charmoniumlike state in $$e^+e^- to D^+_sD^*_{s2}(2573)^-+c.c.$$

Jia, S.*; 谷田 聖; Belle Collaboration*; 他175名*

Physical Review D, 101(9), p.091101_1 - 091101_8, 2020/05

 被引用回数:2 パーセンタイル:15.72(Astronomy & Astrophysics)

We report the measurement of $$e^+e^- to D^+_sD^*_{s2}(2573)^-+c.c.$$ via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb$$^{-1}$$ collected with the Belle detector at the $$Upsilon(4S)$$ and nearby. We find evidence for an enhancement with a 3.4$$sigma$$ significance in the invariant mass of $$D^+_sD^*_{s2}(2573)^- +c.c.$$ The measured mass and width are $$(4619.8^{+8.9}_{-8.0}({rm stat.})pm2.3({rm syst.}))~{rm MeV}/c^{2}$$ and $$(47.0^{+31.3}_{-14.8}({rm stat.})pm4.6({rm syst.}))~{rm MeV}$$, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/$$c^2$$ recently reported by Belle in $$e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$$ The product of the $$e^+e^-to D^+_sD^*_{s2}(2573)^-+c.c.$$ cross section and the branching fraction of $$D^*_{s2}(2573)^-to{bar D}^0K^-$$ is measured from $$D^+_sD^*_{s2}(2573)^-$$ threshold to 5.6 GeV.

論文

Search for an invisibly decaying $$Z^{prime}$$ boson at Belle II in $$e^+ e^- to mu^+ mu^- (e^{pm} mu^{mp})$$ plus missing energy final states

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

 被引用回数:3 パーセンタイル:10.49(Physics, Multidisciplinary)

Theories beyond the standard model often predict the existence of an additional neutral boson, the $$Z^{prime}$$. 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 $$Z^{prime}$$ in the process $$e^+ e^- to mu^+ mu^- Z^{prime}$$ and of a lepton-flavor-violating $$Z^{prime}$$ in $$e^+ e^- to e^{pm} mu^{mp} Z^{prime}$$. 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 $$L_{mu}-L_{tau}$$ theory, into upper limits on the $$Z^{prime}$$ coupling constant at the level of $$5 times 10^{-2}$$ - $$1$$ for $$M_{Z^prime}leq 6$$ GeV/$$c^2$$.

論文

Measurement of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ with a semileptonic tagging method

Caria, G.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review Letters, 124(16), p.161803_1 - 161803_8, 2020/04

 被引用回数:2 パーセンタイル:24.83(Physics, Multidisciplinary)

The experimental results on the ratios of branching fractions $$mathcal{R}(D) = {cal B}(bar{B} to D tau^- bar{nu_{tau}})/{cal B}(bar{B} to D ell^- barnu_{ell})$$ and $$mathcal{R}(D^*) = {cal B}(bar{B} to D^* tau^- bar{nu_{tau}})/{cal B}(bar{B} to D^* ell^- bar{nu_{ell}})$$, where $$ell$$ 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 $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$, based on a data sample containing $$772 times 10^6$$ $$Bbar{B}$$ events recorded at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. In this analysis the tag-side $$B$$ meson is reconstructed in a semileptonic decay mode and the signal-side $$tau$$ is reconstructed in a purely leptonic decay. The measured values are $$mathcal{R}(D)= 0.307 pm 0.037 pm 0.016$$ and $$mathcal{R}(D^*) = 0.283 pm 0.018 pm 0.014$$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $$0.2$$, $$1.1$$ and $$0.8$$ standard deviations for $$mathcal{R}(D)$$, $$mathcal{R}(D^*)$$ and their combination, respectively. This work constitutes the most precise measurements of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ performed to date as well as the first result for $$mathcal{R}(D)$$ based on a semileptonic tagging method.

報告書

先端計測技術の融合で実現する高耐放射線燃料デブリセンサーの研究開発(委託研究); 平成30年度英知を結集した原子力科学技術・人材育成推進事業

廃炉国際共同研究センター; 高エネルギー加速器研究機構*

JAEA-Review 2019-040, 77 Pages, 2020/03

JAEA-Review-2019-040.pdf:4.61MB

日本原子力研究開発機構(JAEA)廃炉国際共同研究センター(CLADS)では、平成30年度英知を結集した原子力科学技術・人材育成推進事業(以下、「本事業」という)を実施している。本事業は、東京電力ホールディングス福島第一原子力発電所の廃炉等をはじめとした原子力分野の課題解決に貢献するため、国内外の英知を結集し、様々な分野の知見や経験を、従前の機関や分野の壁を越えて緊密に融合・連携させた基礎的・基盤的研究及び人材育成を推進することを目的としている。平成30年度の新規採択課題から実施主体を文部科学省からJAEAに移行することで、JAEAとアカデミアとの連携を強化し、廃炉に資する中長期的な研究開発・人材育成をより安定的かつ継続的に実施する体制を構築した。本研究は、研究課題のうち、平成30年度「先端計測技術の融合で実現する高耐放射線燃料デブリセンサーの研究開発」について取りまとめたものである。本研究は、冠水した燃料デブリの分布状況及び臨界性を「その場」で測定・分析することを目的として、小型(200$$mu$$m$$times$$5$$sim$$10$$mu$$m厚)のダイヤモンド中性子センサーと、回路設計により耐放射線性を向上した集積回路を開発して中性子計測システムを構築し、マルチフェイズドアレイ・ソナーや表層下部音波探査装置(SBP)とともに、ROV(日英共研で開発)に設置し、PCV模擬水槽で実証試験を行う。

論文

Successive phase transitions in $$R_{3}$$Ir$$_{4}$$Sn$$_{13}$$ ($$R$$: La and Ce) investigated using neutron and X-ray diffraction

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 $$R_{3}$$Ir$$_{4}$$Sn$$_{13}$$ ($$R$$: La and Ce) were studied using neutron and X-ray diffraction techniques. A semimetal Ce$$_{3}$$Ir$$_{4}$$Sn$$_{13}$$ undergoes three phase transitions: an antiferromagnetic ordering characterized by a propagation vector $$q_{rm M}$$ = (1/2, 1/2, 2/5) below 0.6 K, a structural transformation with $$q_{rm S2}$$= (1/4, 1/4, 1/4) at 2.0 K, and another structural transformation with $$q_{rm S1}$$ = (1/2, 1/2, 0) above room temperature. La$$_{3}$$Ir$$_{4}$$Sn$$_{13}$$ was confirmed to be a superconductor below 2.5 K under the $$q_{rm S1}$$ = (1/2, 1/2, 0) structure that also appears above room temperature.

論文

Study of $$B to p {bar p} pi pi$$

Chu, K.*; 谷田 聖; Belle Collaboration*; 他176名*

Physical Review D, 101(5), p.052012_1 - 052012_8, 2020/03

 被引用回数:0 パーセンタイル:100(Astronomy & Astrophysics)

Using a data sample of $$772 times 10^6$$ BB pairs collected on the $${Upsilon}(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider, we report the observations of $$B^0to p{bar p}pi^+pi^-$$ and $$B^+ to p{bar p}pi^+pi^0$$. We measure a decay branching fraction of $$(0.83 pm 0.17 pm 0.17) times 10^-6$$ in $$B^0to p{bar{p}}pi^+pi^-$$ for $$M_{pi^+pi^-} < 1.22 GeV/c^2$$ with a significance of 5.5 standard deviations. The contribution from $$B0 to p{bar p}K^0$$ is excluded. We measure a decay branching fraction of $$(4.58 pm 1.17 pm 0.67) times 10^-6$$ for $$B^+ to p{bar p}pi^+pi^0$$ with $$M_{pi^+pi^0} < 1.3 GeV/c^2$$ with a significance of 5.4 standard deviations. We study the difference of the $$M_{p{bar p}}$$ distributions in $$B^0to p{bar p}pi^+pi^-$$ and $$B^+ to p{bar p}pi^+pi^0$$.

論文

Observation of the radiative decays of $$Upsilon(1S)$$ to $$chi_{c1}$$

Katrenko, P.*; 谷田 聖; Belle Collaboration*; 他168名*

Physical Review Letters, 124(12), p.122001_1 - 122001_7, 2020/03

 被引用回数:1 パーセンタイル:24.83(Physics, Multidisciplinary)

We report the first observation of the radiative decay of the $$Upsilon(1S)$$ into a charmonium state. The statistical significance of the observed signal of $$Upsilon(1S) to gamma chi_{c1}$$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($$Upsilon(1S) to gamma chi_{c1}$$) = $$(4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) times 10^{-5}$$. We also searched for $$Upsilon(1S)$$ radiative decays into $$chi_{c0,2}$$ and $$eta_c(1S,2S)$$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb$$^{-1}$$ data sample collected with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider at a center-of-mass energy equal to the $$Upsilon(2S)$$ mass using $$Upsilon(1S)$$ tagging by the $$Upsilon(2S) to Upsilon(1S) pi^+pi^-$$ transitions.

論文

Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment

Abudin$'e$n, F.*; 谷田 聖; Belle II Collaboration*; 他420名*

Chinese Physics C, 44(2), p.021001_1 - 021001_12, 2020/02

 被引用回数:2 パーセンタイル:25.8(Physics, Nuclear)

From April to July 2018, a data sample at the peak energy of the $$Upsilon(4S)$$ 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 ($$496.3 pm 0.3 pm 3.0$$) pb$$^{-1}$$, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.

論文

Erratum; The Belle II physics book

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

 被引用回数:5 パーセンタイル:1.73(Physics, Multidisciplinary)

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.

論文

Measurements of the branching fractions $${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}^{'0})$$, $${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2645)^{0})$$ and $${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2790)^{0})$$

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$$^{-1}$$ of $$Upsilon(4S)$$ 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 $$B^{-} to bar{Lambda}_{c}^{-} Xi_{c}^{'0}$$, $$B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2645)^{0}$$, and $$B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2790)^{0}$$. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against $$bar{Lambda}_{c}^{-}$$ baryons in selected $$B^-$$ candidates. The branching fraction of $$B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2790)^{0}$$ is measured to be $$(1.1 pm 0.4 pm 0.2)times 10^{-3}$$, where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on $${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}^{'0})$$ and $${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2645)^{0})$$ are determined to be $$6.5times 10^{-4}$$ and $$7.9times 10^{-4}$$, respectively.

論文

Observation of a vector charmoniumlike state in $$e^+e^- to D^+_sD_{s1}(2536)^-+c.c.$$

Jia, S.*; 谷田 聖; Belle Collaboration*; 他172名*

Physical Review D, 100(11), p.111103_1 - 111103_8, 2019/12

 被引用回数:10 パーセンタイル:12.8(Astronomy & Astrophysics)

Using a data sample of 921.9 fb$$^{-1}$$ collected with the Belle detector, we study the process of $$e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$$ via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to $$D^+_sD_{s1}(2536)^-+c.c.$$ with a significance of 5.9$$sigma$$, including the systematic uncertainties. The measured mass and width are $$(4625.9^{+6.2}_{-6.0}({rm stat.})pm0.4({rm syst.}))~{rm MeV}/c^{2}$$ and $$(49.8^{+13.9}_{-11.5}({rm stat.})pm4.0({rm syst.}))~{rm MeV}$$, respectively. The product of the $$e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$$ cross section and the branching fraction of $$D_{s1}(2536)^-to{bar D}^{*0}K^-$$ is measured from the $$D_s bar{D}_{s1}(2536)$$ threshold to 5.59 GeV.

論文

The Belle II physics book

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

 被引用回数:39 パーセンタイル:0.45(Physics, Multidisciplinary)

We present the physics program of the Belle II experiment, located on the intensity frontier SuperKEKB $$e^+e^-$$ 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, $$phi_1$$ and $$phi_2$$ (time-dependent CP violation) measurements, $$phi_3$$ 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.

論文

Azimuthal asymmetries of back-to-back $$pi^pm-(pi^0,eta,pi^pm)$$ pairs in $$e^+e^-$$ annihilation

Li, H.*; 谷田 聖; Belle Collaboration*; 他131名*

Physical Review D, 100(9), p.092008_1 - 092008_26, 2019/11

 被引用回数:1 パーセンタイル:100(Astronomy & Astrophysics)

This work reports the first observation of azimuthal asymmetries around the thrust axis in $$e^+e^-$$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $$pi^0$$ and $$eta$$ mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The $$pi^0$$ and $$eta$$ asymmetries rise with the relative momentum $$z$$ 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 $$H_1^{perp}$$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the $$eta$$ final states will provide additional information on the flavor structure of $$H_1^{perp}$$. 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$$^{-1}$$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.

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