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論文

Search for the 6$$alpha$$ condensed state in $$^{24}$$Mg using the $$^{12}$$C+$$^{12}$$C scattering

Fujikawa, Y.*; Kawabata, T.*; Adachi, S.*; 廣瀬 健太郎; 牧井 宏之; 西尾 勝久; Orlandi, R.; 洲嵜 ふみ; 他13名*

Physics Letters B, 848, p.138384_1 - 138384_6, 2024/01

https://doi.org/10.1016/j.physletb.2023.138384
 被引用回数：3 パーセンタイル：88.26(Astronomy & Astrophysics)

We searched for the 6$$alpha$$-condensed state in $$^{24}$$Mg by measuring the $$^{12}$$C+$$^{12}$$C scattering with the SAKRA Si detector array. By using the invariant-mass method for the detected 3$$alpha$$ particles, the inclusive cross sections for the $$^{12}$$C+$$^{12}$$C $$rightarrow$$ $$^{12}$$C(0$$^{+}_{2}$$) + X and $$^{12}$$C(3$$^{-}_{1}$$) + X reactions were determined. In both the inclusive $$^{12}$$C(0$$^{+}_{2}$$) + X channel and the exclusive $$^{12}$$C(0$$^{+}_{2}$$) + $$^{12}$$C(0$$^{+}_{1}$$) channel, the cross section peaked at E$$_{cm}$$ = 19.4 MeV, which correspond to the excitation energy of E$$_{x}$$ = 33.3 MeV in $$^{24}$$Mg. This 19.4-MeV state is a candidate for the 6$$alpha$$-condensed state

論文

Evolution of nuclear structure in the neutron-rich $$^{96,97,99}$$Nb isotopes; Evidence for shape coexistence in $$N$$=58 $$^{99}$$Nb

Kumar, V.*; Chapman, R.*; O'Donnell, D.*; Ollier, J.*; Orlandi, R.; Smith, J. F.*; Spohr, K.-M.*; Torres, D. A.*; 他13名*

Physical Review C, 108(4), p.044313_1 - 044313_19, 2023/10

https://doi.org/10.1103/PhysRevC.108.044313
 被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)

The nuclear structure of neutron-rich niobium isotopes $$^{96,97,98}$$Nb were studied at the Legnaro National Laboratories using $$gamma$$-ray spectroscopy. The isotopes were produced in two different experiments, either using multi-nucleon transfer reactions of $$^{96}$$Zr 530-MeV beam onto a $$^{124}$$Sn target, or via fusion-fission of $$^{36}$$S on $$^{176}$$Yb. The level schemes of these isotopes were extended respectively up to excitation energies of 4545, 5409, and 3814 keV. The structure of the low-lying states in these isotopes was interpreted and discussed in the context of shell-model calculations. In particular, for the $$^{99}$$Nb isotope ($$Z$$=41, $$N$$=58), the results indicate the presence of shape-coexistence at low-energies, which was observed for the first time in this isotope.

論文

Precise lifetime measurement of $$^4_Lambda$$H hypernucleus using in-flight $$^4$$He$$(K^-, pi^0)^4_Lambda$$H reaction

赤石 貴也; 橋本 直; 谷田 聖; 他35名*

Physics Letters B, 845, p.138128_1 - 138128_4, 2023/10

https://doi.org/10.1016/j.physletb.2023.138128
 被引用回数：1 パーセンタイル：59.27(Astronomy & Astrophysics)

We present a new measurement of the $$^4_Lambda$$H hypernuclear lifetime using in-flight $$K^-$$ + $$^4$$He $$rightarrow$$ $$^4_Lambda$$H + $$pi^0$$ reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection of the hypernuclear bound state using only the $$gamma$$-ray energy decayed from $$pi^0$$. This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from ($$K^-$$, $$pi^-$$) reaction. As the first application of this method, our result for the $$^4_Lambda$$H lifetime, $$tau(^4_Lambda mathrm{H}) = 206 pm 8 (mathrm{stat.}) pm 12 (mathrm{syst.}) mathrm{ps}$$, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton ($$^3_Lambda$$H) using the same setup in the near future.

論文

$$beta$$-delayed neutron spectroscopy of $$^{133}$$In

Xu, Z. Y.*; Madurga, M.*; Grzywacz, R.*; King, T. T.*; Algora, A.*; Andreyev, A. N.; 他43名*

Physical Review C, 108(1), p.014314_1 - 014314_9, 2023/07

https://doi.org/10.1103/PhysRevC.108.014314
 被引用回数：2 パーセンタイル：79.22(Physics, Nuclear)

Nuclei in the vicinity of doubly magic nuclei away from the line of $$beta$$ stability provide a tremendous testing ground to study the evolution of nuclear shell structure as a function of the unbalance between proton and neutron numbers. The decay $$^{133}$$In (Z=49, N=83), just one proton below and one neutron above doubly magic $$^{132}$$Sn, were studied at the ISOLDE Decay Station. Using the RILIS laser ion source, separate measurements of the 9/2$$^+$$ ground state and 1/2$$^-$$ isomer were carried out. With the use of $$beta$$-delayed neutron and $$gamma$$-ray spectroscopy, the decay strengths above the neutron separation energy were quantified for the first time. The spins and parities to the neutron-unbound states based were assigned based on the $$beta$$-decay selection rules, the log ft values, and systematics. The experimental findings greatly extend the current knowledge of the $$^{133}$$In decay from previous works, providing the $$beta$$-strength distribution southeast of $$^{132}$$Sn.

論文

Pole position of $$Lambda(1405)$$ measured in $$d(K^-,n)piSigma$$ reactions

相川 脩*; 橋本 直; 谷田 聖; 他73名*

Physics Letters B, 837, p.137637_1 - 137637_8, 2023/02

https://doi.org/10.1016/j.physletb.2022.137637
 被引用回数：2 パーセンタイル：47.44(Astronomy & Astrophysics)

We measured a set of $$pi^pmSigma^mp$$, $$pi^0Sigma^0$$, and $$pi^-Sigma^0$$ invariant mass spectra below and above the $$bar{K}N$$ mass threshold in $$K^-$$-induced reactions on deuteron. We deduced the $$S$$-wave$$bar{K}NrightarrowpiSigma$$ and $$bar{K}Nrightarrowbar{K}N$$ scattering amplitudes in the isospin 0 channel in the framework of a $$bar{K}N$$ and $$piSigma$$ coupled channel. We find that a resonance pole corresponding to $$Lambda(1405)$$ is located at 1417.7$$^{+6.0}_{-7.4}$$(fitting errors)$$^{+1.1}_{-1.0}$$(systematic errors) + $$[-26.1^{+6.0}_{-7.9}$$(fitting errors)$$^{+1.7}_{-2.0}$$(systematic errors)]$$i$$ MeV/$$c^2$$, closer to the $$bar{K}N$$ mass threshold than the value determined by the Particle Data Group.

論文

$$Xi^-$$ atomic X-ray spectroscopy using a counter-emulsion hybrid method

藤田 真奈美; 長谷川 勝一; 細見 健二; 市川 真也; 市川 裕大; Kim, S.; 七村 拓野; 佐甲 博之; 田村 裕和; 山本 剛史; et al.

Progress of Theoretical and Experimental Physics (Internet), 2022(12), p.123D01_1 - 123D01_17, 2022/12

https://doi.org/10.1093/ptep/ptac156
 被引用回数：0 パーセンタイル：0.01(Physics, Multidisciplinary)

$$Xi^-$$ atomic X-ray spectroscopy is one of the most useful methods for investigation of the $$Xi$$-nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the $$Xi$$-nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, $$Delta$$E, and the width, $$Gamma$$, give us information on the $$Xi$$-nucleus potential. A serious problem in the measurement is the significant background derived from in-flight $$Xi^-$$ decay. A novel method of identifying stopped $$Xi^-$$ events using the nuclear emulsion was developed to realize the first $$Xi^-$$ atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for $$LambdaLambda$$ and $$Xi^-$$ hypernuclei in the emulsion. The X-rays emitted from $$Xi^-$$ Br and $$Xi^-$$ Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.

論文

First observation of the decay of the 13/2$$^+$$ isomer in $$^{183}$$Hg and $$B$$(${it M}$2) systematics of neutron transitions across the nuclear chart

Huang, H.*; Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Li, Z. H.*; Guo, C. Y.*; Barzakh, A. E.*; Van Duppen, P.*; Andel, B.*; et al.

Physics Letters B, 833, p.137345_1 - 137345_8, 2022/10

https://doi.org/10.1016/j.physletb.2022.137345
 被引用回数：0 パーセンタイル：0.02(Astronomy & Astrophysics)

The decay of the 13/2$$^+$$ isomeric state in $$^{183}$$Hg was observed for the first time following the $$alpha$$ decay of the 13/2$$^+$$ isomer in $$^{187}$$Pb produced in the $$^{142}$$Nd$$(^{50}$$Cr$$, 2p3n)$$ reaction. Using $$alpha$$-$$gamma$$ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) $$mu$$s. This isomer is proposed to deexcite by an unobserved low-energy $$M$$2 transition to the known 9/2$$^-$$ member of a strongly prolate-deformed 7/2$$^-$$[514] band, followed by a 105-keV $$M$$1 transition to the bandhead. A lower limit of B($$M$$2)$$geq$$0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2$$^+$$ isomer in $$^{181}$$Hg, suggesting both are cases of shape isomers. The B($$M$$2) systematics of neutron transitions across the nuclear chart is discussed.

論文

Fine structure in the $$alpha$$ decay of the 8$$^{+}$$ isomer in $$^{216,218}$$U

Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.

Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08

https://doi.org/10.1103/PhysRevC.106.024305
 被引用回数：3 パーセンタイル：61.19(Physics, Nuclear)

The extremely neutron-deficient even-even uranium isotopes $$^{216,218}$$U were produced in the complete-fusion reactions induced by impinging $$^{40}$$Ar and $$^{40}$$Ca ions on $$^{180,182,184}$$W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-$$alpha$$-correlation method. In this paper, we report on new $$alpha$$-decay activities with $$E_{alpha} = 10163(27)$$ keV for $$^{216}$$U and $$E_{alpha} = 10073(16)$$ keV for $$^{218}$$U, which decay from the 8$$^{+}$$ isomeric states of $$^{216,218}$$U into the 2$$^{+}$$ states of their daughter nuclei $$^{212,214}$$Th, respectively. The new results extend the systematics of the $$alpha$$-decay fine structure for the $$N$$ = 124 and 126 even-even isotones.

論文

Identification of excited states in $$^{188}$$Bi and $$^{188}$$Po

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; 他37名*

Physical Review C, 106(2), p.024317_1 - 024317_11, 2022/08

https://doi.org/10.1103/PhysRevC.106.024317
 被引用回数：1 パーセンタイル：28.09(Physics, Nuclear)

The neutron-deficient $$^{188}$$Bi and $$^{188}$$Po isotopes have been studied by $$gamma$$-ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-micro second isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV $$gamma$$ rays have been established on top of the (10$$^{-}$$) $$alpha$$-decaying isomer in $$^{188}$$Bi. The first excited (2$$^{+}$$) state in $$^{188}$$Po was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first 2$$^{+}$$ states in $$^{190,192,194}$$Po. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at $$N$$ = 104. In this mass region, a reduction in the prompt $$gamma$$-ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.

論文

Transport model comparison studies of intermediate-energy heavy-ion collisions

Walter, H.*; Colonna, M.*; Cozma, D.*; Danielewicz, P.*; Ko, C. M.*; Kumar, R.*; 小野 章*; Tsang, M. Y. B*; Xu, J.*; Zhang, Y.-X.*; et al.

Progress in Particle and Nuclear Physics, 125, p.103962_1 - 103962_90, 2022/07

https://doi.org/10.1016/j.ppnp.2022.103962
 被引用回数：51 パーセンタイル：96.94(Physics, Nuclear)

原子核-原子核衝突や原子核の状態方程式の研究において、反応計算モデルは重要なツールとなり、世界中で開発が進んでいる。本論文は、原子力機構のJQMD-2.0を含め、現在開発中の複数のコード開発者の協力により、これらコードを同じ条件で比較することで共通点や差異を明らかにしたプロジェクトTransport Model Evaluation Project (TMEP)を総括したものである。参加したコードはBoltzmann-Uehling-Uhlenbeck(BUU)法に基づく13のコードと、Quantum Molecular Dynamics (QMD)法に基づく12のコードであった。プロジェクトでは、Au原子核同士を衝突させてその終状態を観測する現実的な計算や、一辺が640nmの箱に核子を詰めて時間発展させる仮想的な計算を行った。その結果、BUU法コードとQMD法コードは計算原理が異なるため、計算の設定に関係なく系統的な差異が生じることが明らかになった。その一方で、同じ方法を採用するコード間の比較では、時間発展を細かく計算することでコード間の差は埋まっていき、一定の収束値を持つことが示された。この結果は今後開発される同分野のコードのベンチマークデータとして有用なものであるだけでなく、原子核基礎物理学の実験や理論研究の標準的な指針としても役に立つことが期待される。

論文

First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic $$^{187}$$Pb

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; Li, Z. H.*; Li, J. G.*; Guo, C. Y.*; 他34名*

Physics Letters B, 829, p.137129_1 - 137129_7, 2022/06

https://doi.org/10.1016/j.physletb.2022.137129
 被引用回数：4 パーセンタイル：71.46(Astronomy & Astrophysics)

Prompt and delayed $$gamma$$-ray spectroscopy of the neutron-deficient, semi-magic isotope $$^{187}$$Pb has been performed at the Argonne Gas-Filled Analyzer. A new 5.15(15)-$$mu$$s isomeric state at only 308 keV above the spherical 3/2$$^{-}$$ ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2$$^{-}$$[514] Nilsson state in the isotone $$^{185}$$Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in $$^{187}$$Pb is proposed to originate from the same configuration. The retarded character of the 308-keV transition can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The combined results of the present work and the previous $$alpha$$-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of $$^{187}$$Pb, which is well reproduced by the potential-energy surface calculations.

論文

Magnetic phase diagram of helimagnetic Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ (0 $$leq$$ x $$leq$$ 0.2) hexagonal ferrite

丸山 建一*; 田中 誠也*; 鬼柳 亮嗣; 中尾 朗子*; 森山 健太郎*; 石川 喜久*; 天児 寧*; 飯山 拓*; 二村 竜祐*; 内海 重宣*; et al.

Journal of Alloys and Compounds, 892, p.162125_1 - 162125_8, 2022/02

https://doi.org/10.1016/j.jallcom.2021.162125
 被引用回数：2 パーセンタイル：15.51(Chemistry, Physical)

Hexagonal ferrite Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ is an important magnetic oxide material in both science and engineering because it exhibits helimagnetism around room temperature (300 K). In this study, the magnetic phase diagram of Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ consisting of ferri-, heli-, antiferro-, and paramagnetic phases has been completed through magnetization and neutron diffraction measurements. The magnetic phase transition temperature to paramagnetism decreases with the increase in x, and the temperature at which the magnetization reaches a maximum, which corresponds to the magnetic phase transition from heli- to ferrimagnetism, is determined for low x crystals. The temperatures at which helimagnetism appears are precisely determined by observing the magnetic satellite reflection peaks in neutron diffraction at various temperatures, which characterize helimagnetism. Based on these results, the magnetic phase diagram of the Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ system is constructed in the T-x plane. Helimagnetism appears at x $$>$$ 0.06, and magnetism with antiferromagnetic components appears as the extension phase of helimagnetism at x $$>$$ 0.19 through the coexistence region. The turn angle $$phi_{0}$$ of the helix for each x crystal is calculated from the relationship, $$phi_{0} = 2pidelta$$, where $$delta$$ is the incommensurability. The turn angle $$phi_{0}$$ decreases with the increase in temperature for the same x crystal, and increases with the increase in x at the same temperature. Furthermore, it is found that there are clear thresholds at which $$phi_{0}$$ cannot take values between 0$$^{circ}$$ < $$phi_{0}$$ < 90$$^{circ}$$ and 170$$^{circ}$$ < $$phi_{0}$$ < 180$$^{circ}$$.

論文

Producing gold at ISOLDE-CERN

Barzakh, A. E.*; Andreyev, A. N.; Atanasov, D.*; Cubiss, J. G.*; Harding, R. D.*; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; 他38名*

Nuclear Instruments and Methods in Physics Research B, 513, p.26 - 32, 2022/02

https://doi.org/10.1016/j.nimb.2021.12.011
 被引用回数：0 パーセンタイル：0.02(Instruments & Instrumentation)

The yield of 18 beams of radioactive gold nuclei produced by irradiating the ISOLDE uranium target with 1.4-GeV protons was measured. The production-efficiency dependence on the half-life was derived using the in-target production calculations. Three release models were tested to describe the results. Irregularities in the efficiency curve for 3 long-lived high-spin gold isomers ($$^{187,191,193}$$Au$$^m$$) were found, which require further investigation.

論文

Large shape staggering in neutron-deficient Bi isotopes

Barzakh, A.*; Andreyev, A. N.; Raison, C.*; Cubiss, J. G.*; 他53名*

Physical Review Letters, 127(19), p.192501_1 - 192501_7, 2021/11

https://doi.org/10.1103/PhysRevLett.127.192501
 被引用回数：23 パーセンタイル：90.14(Physics, Multidisciplinary)

The changes in the mean-square charge radius (relative to $$^{209}$$Bi, magnetic moments and quadrupole moments of the neutron-deficient bismuth isotopes $$^{187,188,189,190}$$Bi were measured at ISOLDE (CERN). In the experiment, the in-source resonance-ionization spectroscopy technique was employed, which permits to study isotopes produced with rates as low as 0.1/sec. The radii of $$^{187.188.189}$$Bi manifest a large staggering, corresponding to a sudden increase of the radius of $$^{188}$$Bi relative to its $$^{187,189}$$Bi neighbors. This staggering effect occurs at neutron number $$N$$=105, where shape staggering was also observed in the mercury isotopes. Experimental results were compared with state-of-the-art mean-field calculations, which permit to identify the quasiparticle configurations compatible with the observed spin, parity and magnetic moment of the newly observed states.

論文

Precise measurement of the $$D^0$$ and $$D^+$$ lifetimes at Belle II

Abudin$'e$n, F.*; 谷田 聖; Belle II Collaboration*; 他385名*

Physical Review Letters, 127(21), p.211801_1 - 211801_9, 2021/11

https://doi.org/10.1103/PhysRevLett.127.211801
 被引用回数：6 パーセンタイル：59.12(Physics, Multidisciplinary)

We report a measurement of the $$D^0$$ and $$D^+$$ lifetimes using $$D^0to K^-pi^+$$ and $$D^+to K^-pi^+pi^+$$ decays reconstructed in $$e^+e^-to cbar{c}$$ data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy $$e^+e^-$$ collider. The data, collected at center-of-mass energies at or near the $$Upsilon(4S)$$ resonance, correspond to an integrated luminosity of $$72,{rm fb}^{-1}$$. The results, $$tau(D^0) = 410.5pm1.1,{rm(stat)}pm0.8,{rm(syst.)},{rm fs}$$ and $$tau(D^+) = 1030.4pm4.7,{rm(stat)}pm3.1,{rm(syst.)},{rm fs}$$, are the most precise to date and are consistent with previous determinations.

論文

Measurement of the branching fraction of $$Lambda_c^+ to p omega$$ decay at Belle

Li, S. X.*; 谷田 聖; Belle Collaboration*; 他193名*

Physical Review D, 104(7), p.072008_1 - 072008_8, 2021/10

https://doi.org/10.1103/PhysRevD.104.072008
 被引用回数：3 パーセンタイル：27.57(Astronomy & Astrophysics)

Using 980.6 $$rm fb^{-1}$$ of data collected with the Belle detector operating at the KEKB asymmetric-energy $$e^+e^-$$ collider, we present a measurement of the branching fraction of the singly Cabibbo-suppressed decay $$Lambda_c^+ to p omega$$. A clear $$Lambda_c^+$$ signal is observed for $$Lambda_c^+ to p omega$$ with a statistical significance of 9.1 standard deviations, and we measure the ratio of branching fractions $${cal B}(Lambda_c^+ to p omega)/{cal B}(Lambda_c^+ to p K^- pi^+) = (1.32 pm 0.12 (rm stat) pm 0.10 (rm syst))times 10^{-2}$$, from which we infer the branching fraction $${cal B}(Lambda_c^+ to p omega) = (8.27 pm 0.75 (rm stat) pm 0.62 (rm syst) pm 0.42 (rm ref))times 10^{-4}$$. The first quoted uncertainty is statistical, the second systematic, and the third from the reference mode $$Lambda_c^+ to p K^- pi^+$$.

論文

Probing gluon spin-momentum correlations in transversely polarized protons through midrapidity isolated direct photons in $$p^uparrow+p$$ collisions at $$sqrt{s}$$=200 GeV

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他306名*

Physical Review Letters, 127(16), p.162001_1 - 162001_8, 2021/10

https://doi.org/10.1103/PhysRevLett.127.162001
 被引用回数：8 パーセンタイル：67.41(Physics, Multidisciplinary)

Studying spin-momentum correlations in hadronic collisions offers a glimpse into a three-dimensional picture of proton structure. The transverse single-spin asymmetry for midrapidity isolated direct photons in $$p^uparrow+p$$ collisions at $$sqrt{s}$$=200 GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). Because direct photons in particular are produced from the hard scattering and do not interact via the strong force, this measurement is a clean probe of initial-state spin-momentum correlations inside the proton and is in particular sensitive to gluon interference effects within the proton. This is the first time direct photons have been used as a probe of spin-momentum correlations at RHIC. The uncertainties on the results are a fifty-fold improvement with respect to those of the one prior measurement for the same observable, from the Fermilab E704 experiment. These results constrain gluon spin-momentum correlations in transversely polarized protons.

論文

Measurements of partial branching fractions of inclusive $$B to X_u , ell^+, nu_{ell}$$ decays with hadronic tagging

Cao, L.*; 谷田 聖; Belle Collaboration*; 他236名*

Physical Review D, 104(1), p.012008_1 - 012008_32, 2021/07

https://doi.org/10.1103/PhysRevD.104.012008
 被引用回数：10 パーセンタイル：65.88(Astronomy & Astrophysics)

We present measurements of partial branching fractions of inclusive semileptonic $$B to X_u , ell^+, nu_{ell}$$ decays using the full Belle data set of 711 fb$$^{-1}$$ of integrated luminosity at the $$Upsilon(4S)$$ resonance and for $$ell = e, mu$$. Inclusive semileptonic $$B to X_u , ell^+, nu_{ell}$$ decays are CKM suppressed and measurements are complicated by the large background from CKM-favored $$B to X_c , ell^+, nu_{ell}$$ transitions, which have a similar signature. Using machine learning techniques, we reduce this and other backgrounds effectively, whilst retaining access to a large fraction of the $$B to X_u , ell^+, nu_{ell}$$ phase space and high signal efficiency. We measure partial branching fractions in three phase-space regions covering about $$31%$$ to $$86%$$ of the accessible $$B to X_u , ell^+, nu_{ell}$$ phase space. The most inclusive measurement corresponds to the phase space with lepton energies of $$E_ell^B > 1 $$ GeV, and we obtain $$Delta mathcal{B}(B to X_u ell^+ , nu_ell) = left( 1.59 pm 0.07 pm 0.16 right) times 10^{-3}$$ from a two-dimensional fit of the hadronic mass spectrum and the four-momentum-transfer squared distribution, with the uncertainties denoting the statistical and systematic error. We find $$left|V_{ub} right| = left( 4.10 pm 0.09 pm 0.22 pm 0.15 right) times 10^{-3}$$ from an average of four calculations for the partial decay rate with the third uncertainty denoting the average theory error. This value is higher but compatible with the determination from exclusive semileptonic decays within 1.3 standard deviations.

論文

First observation of a nuclear $$s$$-state of a $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$

吉本 雅浩*; 藤田 真奈美; 橋本 直; 早川 修平; 市川 裕大; 市川 真也; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Progress of Theoretical and Experimental Physics (Internet), 2021(7), p.073D02_1 - 073D02_19, 2021/07

https://doi.org/10.1093/ptep/ptab073
 被引用回数：13 パーセンタイル：79.65(Physics, Multidisciplinary)

Bound-systems of $$Xi^-$$-$$^{14}_{}{rm N}$$ are studied via $$Xi^-$$ capture at rest followed by emission of a twin single-$$Lambda$$ hypernucleus in the emulsion detectors. Two events forming extremely deep $$Xi^-$$ bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as $$Xi^-+^{14}_{}{rm N}to^{5}_{Lambda}{rm He}$$+$$^{5}_{Lambda}{rm He}$$+$$^{4}_{}{rm He}$$+$$n$$. Since there are no excited states for daughter particles, the binding energy of the $$Xi^-$$ hyperon, $$B_{Xi^-}$$, in $$^{14}_{}{rm N}$$ nucleus was uniquely determined to be 6.27 $$pm$$ 0.27 MeV. Another $$Xi^-$$-$$^{14}_{}{rm N}$$ system via the decay $$^{9}_{Lambda}{rm Be}$$ + $$^{5}_{Lambda}{rm He}$$ + $$n$$ brings a $$B_{Xi^-}$$ value, 8.00 $$pm$$ 0.77 MeV or 4.96 $$pm$$ 0.77 MeV, where the two possible values of $$B_{Xi^-}$$ correspond to the ground and the excited states of the daughter $$^{9}_{Lambda}{rm Be}$$ nucleus, respectively. Because the $$B_{Xi^-}$$ values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear $$1p$$ state of the $$Xi^-$$-$$^{14}_{}{rm N}$$ system, these new events give the first indication of the nuclear $$1s$$ state of the $$Xi$$ hypernucleus, $$^{15}_{Xi}{rm C}$$.

論文

Measurement of the resonant and nonresonant branching ratios in $$Xi_{c}^{0} rightarrow Xi^{0} K^+ K^-$$

McNeil, J. T.*; 谷田 聖; Belle Collaboration*; 他193名*

Physical Review D, 103(11), p.112002_1 - 112002_11, 2021/06

https://doi.org/10.1103/PhysRevD.103.112002
 被引用回数：3 パーセンタイル：27.57(Astronomy & Astrophysics)

Using the entire data sample of $$980$$ $$rm fb^{-1}$$ integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy $$e^{+}e^{-}$$ collider, we present an amplitude analysis measuring the branching fractions of the Cabibbo-allowed, $$W$$-exchange resonant decay $$Xi_{c}^{0} rightarrow Xi^{0} phi (to K^+ K^-)$$ with a polarized $$phi$$ and the non-resonant decay via a direct process $$Xi_{c}^{0} rightarrow Xi^{0} K^+ K^-$$. We present these measurements, relative to the normalization mode $$Xi^{-}pi^{+}$$, and find branching ratios $$frac{mathcal{B}(Xi_{c}^{0} rightarrow Xi^{0} phi (rightarrow K^{+}K^{-}))}{mathcal{B}(Xi_{c}^{0} rightarrow Xi^{-} pi^{+})}$$ = $${rm 0.036 pm 0.004 (stat.) pm 0.002 (syst.)}$$ and $$frac{mathcal{B}(Xi_{c}^{0} rightarrow Xi^{0} K^{+} K^{-})}{mathcal{B}(Xi_{c}^{0} rightarrow Xi^{-} pi^{+})}$$ = $$ 0.039 pm 0.004 ({rm stat.}) pm 0.002 {rm (syst.)}$$ which suggest that only minor cusping peaks occur in the combinatorial background of $$Omega^{*-} to Xi^{0}K^{-}$$ due to these $$Xi_{c}^{0}$$ decays.

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