Publications (11)39.04 Total impact
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Article: γ-ray spectroscopy of Λ16O and Λ15N hypernuclei via the 16O(K-,π-γ) reaction
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ABSTRACT: The bound-state level structures of the Λ16O and Λ15N hypernuclei were studied by γ-ray spectroscopy using a germanium detector array (Hyperball) via the 16O (K-,π-γ) reaction. A level scheme for Λ16O was determined from the observation of three γ-ray transitions from the doublet of states (2-,1-) at ~6.7 MeV to the ground-state doublet (1-,0-). The Λ15N hypernuclei were produced via proton emission from unbound states in Λ16O. Three γ rays were observed, and the lifetime of the 1/2+;1 state in Λ15N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin dependence of the ΛN interaction is discussed. In particular, the measured Λ16O ground-state doublet spacing of 26.4±1.6±0.5 keV determines a small but nonzero strength of the ΛN tensor interaction.Phys. Rev. C. 05/2008; 77(5). -
Article: γ -ray spectroscopy study of 11ΛB and 12ΛC
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ABSTRACT: In this paper, a preliminary result from the latest hypernuclear γ -ray spectroscopy experiment (KEK-E566) is presented together with a short discussion. The experiment was performed at the KEK-PS K6 beam line in 2005. In this experiment, the 12C(π+, K +)12 ΛC reaction was employed to populate 12 ΛC/11 ΛB hypernuclei. A germanium detector array, Hyperball2, was constructed to detect γ -rays emitted from the hypernuclei produced. Three hypernuclear γ -ray peaks were observed and assigned.European Physical Journal A 08/2007; 33(3):243-246. · 2.19 Impact Factor -
Chapter: Plan for the measurement of Ξ−-atomic X rays at J-PARC
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ABSTRACT: We present our plan to measure X rays from Ξ − atoms for the first time in the world at J-PARC. The measurement of X rays from Ξ − atoms is a promising method to study the optical potential between Ξ − and a nucleus as proved in the cases of other negative hadrons (π −, K −, $ \bar p $ \bar p , and Σ −). While we are intending to measure X rays from as many targets as possible over the periodic table, we have chosen Fe (iron) as the first target because the measurement will be the easiest and because large X-ray energy shift and width may be expected. Choice of other targets will be determined based on the result of the first experiment. We can accumulate several thousand counts of X rays and determine its energy shift down to ∼0.05 keV. This is sensitive enough to observe expected energy shift (∼1 keV) with reasonable accuracy, while sensitivities for X-ray width is somewhat weaker (measurable down to ∼1 keV).12/2006: pages 145-148; -
Article: Hypernuclear fine structure in (16)(Lambda)O and the LambdaN tensor interaction.
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ABSTRACT: We have observed two gamma-ray transitions in (16)(Lambda)O from the 6.6 MeV excited 1(-)(2) state to both ground-state spin-doublet members (1(-)(1),0(-)) by the (K-,pi(-)gamma) reaction. We have obtained the ground-state doublet spacing to be 26.4+/-1.6(stat)+/-0.5(syst) keV and the excitation energy of the 1(-)(2) state to be 6561.7+/-1.1(stat)+/-1.7(syst) keV. The ground-state doublet spacing provides a small but nonzero strength of the tensor interaction between a Lambda and a nucleon. This is the first experimental result on the LambdaN tensor interaction.Physical Review Letters 01/2005; 93(23):232501. · 7.37 Impact Factor -
Article: Σ-nucleus potential studied with the (π−,K+) reaction on medium-to-heavy nuclear targets
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ABSTRACT: In order to study the Σ-nucleus optical potential, we measured inclusive (π−,K+) spectra on medium-to-heavy nuclear targets CH2, Si, Ni, In, and Bi. The CH2 target was used to calibrate the excitation energy scale by using the elementary process p+π−→K++Σ−, where the C spectrum was also extracted. The calibration was done with ±0.1 MeV precision. The angular distribution of the elementary cross section was measured and agreed well with the previous bubble chamber data, but with better statistics, and the magnitudes of the cross sections of the measured inclusive (π−,K+) spectra were also well calibrated. All of the inclusive spectra were found to be similar in shape at a region near to the Σ− binding energy threshold, showing a weak mass-number dependence on the magnitude of the cross section. The measured spectra were compared with a theoretical calculation performed within the framework of the distorted-wave impulse approximation. It has been demonstrated that a strongly repulsive Σ-nucleus potential with a nonzero size of the imaginary part is required to reproduce the shape of the measured spectra.Phys. Rev. C. 10/2004; 70(4). -
Article: Study of the Sigma-nucleus potential by the (pi^-,K^+) reaction on medium-to-heavy nuclear targets
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ABSTRACT: In order to study the Sigma-nucleus optical potential, we measured inclusive (pi^-,K^+) spectra on medium-to-heavy nuclear targets: CH_2, Si, Ni, In and Bi. The CH_2 target was used to calibrate the excitation energy scale by using the elementary process p + pi^- -> K^+ + Sigma^-, where the C spectrum was also extracted. The calibration was done with +-0.1 MeV precision. The angular distribution of the elementary cross section was measured, and agreed well with the previous bubble chamber data, but with better statistics, and the magnitudes of the cross sections of the measured inclusive (pi^-,K^+) spectra were also well calibrated. All of the inclusive spectra were found to be similar in shape at a region near to the Sigma^- binding energy threshold, showing a weak mass-number dependence on the magnitude of the cross section. The measured spectra were compared with a theoretical calculation performed within the framework of the Distorted Wave Impulse Approximation (DWIA). It has been demonstrated that a strongly repulsive \sig-nucleus potential with a non-zero size of the imaginary part is required to reproduce the shape of the measured spectra. Comment: 21 pages, 24 figures, submitted to PRC05/2004; -
Article: Sigma-nucleus potential in A=28.
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ABSTRACT: We have studied the (pi(-),K+) reaction on a silicon target to investigate the sigma-nucleus potential. The inclusive spectrum was measured at a beam momentum of 1.2 GeV/c with an energy resolution of 3.3 MeV (FWHM) by employing the superconducting kaon spectrometer system. The spectrum was compared with theoretical calculations within the framework of the distorted-wave impulse approximation, which demonstrates that a strongly repulsive sigma-nucleus potential with a nonzero size of the imaginary part reproduces the observed spectrum.Physical Review Letters 09/2002; 89(7):072301. · 7.37 Impact Factor -
Article: Hypernuclear fine structure in (9)(lambda)Be.
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ABSTRACT: With a germanium detector array (Hyperball), we observed two gamma-ray peaks corresponding to the two transitions (5/2(+)-->1/2(+) and 3/2(+)-->1/2(+)) in the (9)(Lambda)Be hypernucleus which was produced by the 9Be(K-,pi(-)) reaction. The energies of the gamma rays are 3029 +/- 2 +/- 1 keV and 3060 +/- 2 +/- 1 keV. The energy difference was measured to be 31.4(+2.5)(-3.6) keV, which indicates a very small Lambda-spin-dependent spin-orbit force between a Lambda and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus.Physical Review Letters 02/2002; 88(8):082501. · 7.37 Impact Factor -
Article: Measurement of the B(e2) of (7)(lambda)Li and shrinkage of the hypernuclear size.
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ABSTRACT: We report on the first measurement of a hypernuclear gamma-transition probability. gamma rays emitted in the E2(5/2(+)-->1/2(+)) transition of (7)(Lambda)Li were detected by a large-acceptance germanium detector array (Hyperball), and the lifetime of the parent state ( 5/2(+)) was determined by the Doppler shift attenuation method. The obtained result, 5.8(+0.9)(-0.7)+/-0.7 ps, was then converted into the reduced transition probability [ B(E2)] to be B(E2;5/2(+)-->1/2(+)) = 3.6+/-0.5(+0.5)(-0.4) e(2) fm(4). Compared with the B(E2) of the corresponding E2(3(+)-->1(+)) transition in the 6Li nucleus, our result gives evidence that the size of the 6Li core in (7)(Lambda)Li is smaller than the 6Li nucleus in the free space.Physical Review Letters 03/2001; 86(10):1982-5. · 7.37 Impact Factor -
Article: Observation of a spin-flip M1 transition in 7(lambda)Li.
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ABSTRACT: Using a large-acceptance germanium detector array (Hyperball), we have observed a spin-flip M1 gamma transition between the ground-state spin doublet of (7)(Lambda)Li (3/2(+)-->1/2(+)). The observed energy of 691.7+/-0.6(stat)+/-1.0(syst) keV provides crucial information on the strength of the spin-spin interaction between a Lambda and a nucleon. This is the first observation of well-identified hypernuclear gamma transitions using germanium detectors.Physical Review Letters 06/2000; 84(26 Pt 1):5963-6. · 7.37 Impact Factor -
Article: Cascade γ decay in the Λ7Li hypernucleus
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ABSTRACT: In a γ-ray spectroscopy experiment with the (K-,π-) reaction on a 10B target, we have observed the 7/2+→5/2+ spin-flip M1 transition in Λ7Li via γ-γ coincidence with the 5/2+→1/2+E2 transition. This is the first successful γ-γ coincidence measurement for hypernuclei. The measured M1 γ-ray energy is 470.8±1.9(stat)±0.6(syst) keV. The spacing of the 7/2+,5/2+ doublet is consistently explained using the strengths of the spin-spin, Λ-spin-orbit, and tensor interactions obtained from previous γ-spectroscopy experiments.Phys. Rev. C. 73(1).
Top co-authors
Top Journals
Institutions
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2006–2008
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China Institute of Atomic Energy
Beijing, Beijing Shi, China
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2000–2005
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Tohoku University
- Department of Physics
Sendai-shi, Miyagi-ken, Japan
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2001
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The University of Tokyo
- Department of Physics
Tokyo, Tokyo-to, Japan
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