M. Kamimura

RIKEN, Вако, Saitama, Japan

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Publications (166)341.4 Total impact

  • E. Hiyama · M. Isaka · M. Kamimura · T. Myo · T. Motoba
    Physical Review C 05/2015; 91(5). DOI:10.1103/PhysRevC.91.054316 · 3.88 Impact Factor
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    E. Hiyama · M. Isaka · M. Kamimura · T. Myo · T. Motoba
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    ABSTRACT: The structure of neutron-rich $\Lambda$ hypernucleus, $^7_{\Lambda}$He is studied within the framework of an $\alpha +\Lambda +n+n$ four-body cluster model. We predict second $3/2^+$ and $5/2^+$ states, corresponding to a $0s$ $\Lambda$ coupled to the second $2^+$ state of $^6$He, as narrow resonant states with widths $\Gamma \sim 1$ MeV to be at 0.03 MeV and 0.07 MeV respect to the $\alpha +\Lambda +n+n$ threshold. From an estimation of the differential cross section for the $^7{\rm Li} (\gamma,K^+) ^7_{\Lambda}$He reaction, there is a possibility to observe these state at JLab in the future. We also calculate the second $2^+$ state of $^6$He as resonant state within the framework of an $\alpha +n+n$ three-body cluster model. Our result is $2.81$ MeV with $\Gamma =$4.63 MeV with respect to the $\alpha +n+n$ threshold. This energy position is $\sim 1$ MeV higher, and with a much broader decay width, than the recent SPIRAL data. It is suggested that an experiment at JLab to search for the second $3/2^+$ and $5/2^+$ states of $^7_{\Lambda}$He would provide an opportunity to confirm the second $2^+$ state of the core nucleus $^6$He.
  • S Ohtsubo · Y Fukushima · M Kamimura · E Hiyama
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    ABSTRACT: We have developed the complex-scaling method (CSM) by using the complex-range (or oscillating) Gaussian basis functions that are suited for describing highly oscillating few-body wave functions. The eigenvalue distribution of the complex scaled Hamiltonian becomes much more precise and the maximum scaling angle becomes drastically larger than those given by the use of real-range Gaussians. Owing to this advantage, we were able to isolate the S-matrix pole of the new broad 0+3 resonance from the 3α continuum. This confirms the Kurokawa-Kato's prediction (2005) of the new 0+3 resonance, which is considered to correspond to the newly observed 0+3 resonance (Ex = 9.04 MeV, Γ = 1.45 MeV) by Itoh et al. (2013). As a result the long-standing puzzle for the 0+ and 2+ resonances above the 0+ Hoyle state in 12C was solved. In this paper, the negative parity resonances with J = 1−, 2−, 3−, 4− and 5− are newly calculated.
    Journal of Physics Conference Series 12/2014; 569(1). DOI:10.1088/1742-6596/569/1/012070
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    E. Hiyama · M. Kamimura
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    ABSTRACT: We calculated, using seven realistic 4He-4He potentials in the literature, the Efimov spectra of the 4He trimer and tetramer and analyzed the universality of the systems. The three-(four-)body Schroedinger equations were solved fully nonadiabatically with the high-precision calculation method employed in our previous work on the 4He trimer and tetramer [Phys. Rev. A 85, 022502 (2012); 85, 062505 (2012)]. We found the following universality in the four-boson system: i) The critical scattering lengths at which the tetramer ground and excited states couple to the four-body threshold are independent of the choice of the two-body realistic potentials in spite of the difference in the short-range details and are consistent with the corresponding values observed in the experiments in ultracold alkali atoms when scaled with the van der Waals length r_vdW, and ii) the four-body hyperradial potential has a repulsive barrier at the four-body hyperradius R_4 \approx 3 r_vdW, which prevents the four particles from getting close together to explore nonuniversal features of the interactions at short distances. This result is an extension of the universality in Efimov trimers that the appearance of the repulsive barrier at the three-body hyperradius R_3 \approx 2 r_vdW makes the critical scattering lengths independent of the short-range details of the interactions as reported in the literature and also in the present work for the 4He trimer with the realistic potentials.
    Physical Review A 09/2014; 90(5). DOI:10.1103/PhysRevA.90.052514 · 2.99 Impact Factor
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    ABSTRACT: The triple α reaction rate in stars is quite important in many astrophysical scenarios including the stellar evolution and carbon synthesis in stars. Recently the non-resonant triple α reaction rate has been reevaluated using a calculation with the continuum-discretized coupled-channels (CDCC) method, which dramatically increased the rate at low temperature compared to the widely-used NACRE compilation. Since the enhancement influences strongly on astrophysical model simulations, we have planned an experiment for drawing conclusion on the non-resonant triple α reaction rate at low temperature by measuring the three-α continuum state in 12C. We report the present situation of the experiment.
    Few-Body Systems 08/2013; 54(7-10). DOI:10.1007/s00601-013-0697-y · 1.51 Impact Factor
  • H. Suno · E. Hiyama · M. Kamimura
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    ABSTRACT: The triatomic 4He system and its isotopic species ${^4{\rm He}_2^3{\rm He}}$ are theoretically investigated. By adopting the best empirical helium interaction potentials, we calculate the bound state energy levels as well as the rates for the three-body recombination processes: 4He + 4He + 4He → 4 He2 + 4He and 4He + 4He + 3He → 4He2 + 3He. We consider not only zero total angular momentum J = 0 states, but also J > 0 states. We also extend our study to mixed helium-alkali triatomic systems, that is 4He2X with X = 7Li, 23Na, 39K, 85 Rb, and 133Cs. The energy levels of all the J ≥ 0 bound states for these species are calculated as well as the rates for three-body recombination processes such as 4He + 4He + 7Li → 4 He2 + 7Li and 4He + 4He + 7Li → 4 He7Li + 4He. In our calculations, the adiabatic hyperspherical representation is employed but we also obtain preliminary results using the Gaussian expansion method.
    Few-Body Systems 08/2013; 54(7-10). DOI:10.1007/s00601-013-0708-z · 1.51 Impact Factor
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    E. Hiyama · S. Ohnishi · M. Kamimura · Y. Yamamoto
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    ABSTRACT: The structure of heavy hyperhydrogen $^6_{\Lambda}$H is studied within the framework of a $tnn\Lambda$ four-body cluster model. Interactions among the constituent subunits are determined so as to reproduce reasonably well the observed low-energy properties of the $tn, t\Lambda$ and $tnn$ subsystems. As long as we reproduce the energy and width of $^5$H within the error bar, the ground state of $^6_{\Lambda}$H is obtained as a resonant state.
    Nuclear Physics A 06/2013; 908:29–39. DOI:10.1016/j.nuclphysa.2013.04.001 · 2.50 Impact Factor
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    ABSTRACT: We propose to use the complex-range Gaussian basis functions, {r^l e^{-(1 \pm i\omega)(r/r_n)^2}Y_{lm}(\hat{r}); r_n in a geometric progression}, in the calculation of three-body resonances with the complex-scaling method (CSM) in which use is often made of the real-range Gaussian basis functions, {r^l e^{-(r/r_n)^2}Y_{lm}(\hat{r})}, that are suitable for describing the short-distance structure and the asymptotic decaying behavior of few-body systems. The former basis set is more powerful than the latter when describing the resonant and nonresonant continuum states with highly oscillating amplitude at large scaling angles \theta. We applied the new basis functions to the CSM calculation of the 3\alpha resonances with J=0^+, 2^+ and 4^+ in 12C. The eigenvalue distribution of the complex scaled Hamiltonian becomes more precise and the maximum scaling angle becomes drastically larger (\theta_{max}=16 deg. \arrow 36 deg.) than those given by the use of the real-range Gaussians. Owing to these advantages, we were able to confirm the prediction by Kurokawa and Kato [Phys. Rev. C 71, 021301 (2005)] on the appearance of the new broad 0^+_3 state; we show it as an explicit resonance pole isolated from the 3$\alpha$ continuum.
    02/2013; 2013(7). DOI:10.1093/ptep/ptt048
  • Emiko Hiyama · Masayasu Kamimura
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    ABSTRACT: Gaussian Expansion Method has been applied to four-body calculations of ${^4_{\Lambda}{\rm H}}$ and ${^4_{\Lambda}{\rm He}}$ , and four-body calculation of 4He tetramer. We found that Λ N− Σ N coupling is important to make bound A = 4 hypernuclei. The binding energies of the tetramer ground state and excited states are obtained as 558.98 and 127.33 mK.
    Few-Body Systems 05/2012; 54(5-6). DOI:10.1007/s00601-012-0471-6 · 1.51 Impact Factor
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    E. Hiyama · M. Kamimura
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    ABSTRACT: In a previous work [Phys. Rev. A 85, 022502 (2012)] we calculated, with the use of our Gaussian expansion method for few-body systems, the energy levels and spatial structure of the 4He trimer and tetramer ground and excited states using the LM2M2 potential, which has a very strong short-range repulsion. In this work, we calculate the same quantities using the presently most accurate 4He-4He potential [M. Przybytek et al., Phys. Rev. Lett. 104, 183003 (2010)] that includes the adiabatic, relativistic, QED and residual retardation corrections. Contributions of the corrections to the tetramer ground-(excited-)state energy, -573.90 (-132.70) mK, are found to be, respectively, -4.13 (-1.52) mK, +9.37 (+3.48) mK, -1.20 (-0.46) mK and +0.16 (+0.07) mK. Further including other realistic 4He potentials, we calculated the binding energies of the trimer and tetramer ground and excited states, B_3^(0), B_3^(1), B_4^(0) and B_4^(1), respectively. We found that the four kinds of the energies for the different potentials exhibit perfect linear correlations between any two of them over the range of binding energies relevant for 4He atoms (namely, six types of the generalized Tjon lines are given). The dimerlike-pair model for 4He clusters, proposed in the previous work, predicts a simple universal relation B_4^(1)/B_2 =B_3^(0)/B_2 + 2/3, which precisely explains the correlation between the tetramer excited-state energy and the trimer ground-state energy, with B_2 being the dimer binding energy.
    Physical Review A 03/2012; 85(6). DOI:10.1103/PhysRevA.85.062505 · 2.99 Impact Factor
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    ABSTRACT: The gravitino of mass 10-100 GeV is a well motivated scenario in supergravity. If the stau is the next lightest supersymmetry particle, its life-time becomes order of $10^{6-8}$ sec. If it is the case the stau makes a big impact on the nuclear fusion, since it is a charged particle. In this paper we perform a detailed calculation of a stau-catalyzed d-t fusion. We find that if certain technical conditions are satisfied, it is not hopeless to use the nuclear fusion as a source of energy.
  • E.hiyama · M.kamimura · T.motoba · T.yamada · Y.yamamoto
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    ABSTRACT: On the basis of the three- and four-body structure calculations of and , , , , , and , it is emphasized that there are many interesting and important few-body problems in hypernuclear physics.
    Modern Physics Letters A 11/2011; 18(02n06). DOI:10.1142/S021773230301003X · 1.34 Impact Factor
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    Emiko Hiyama · Masayasu Kamimura
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    ABSTRACT: We calculated the 4He trimer and tetramer ground and excited states with the LM2M2 potential using our Gaussian expansion method (GEM) for ab initio variational calculations of few-body systems. The method has extensively been used for a variety of three-, four- and five-body systems in nuclear physics and exotic atomic/molecular physics. The trimer (tetramer) wave function is expanded in terms of symmetric three-(four-)body Gaussian basis functions, ranging from very compact to very diffuse, without assuming any pair correlation function. Calculated results of the trimer ground and excited states are in excellent agreement with the literature. Binding energies of the tetramer ground and excited states are obtained to be 558.98 mK and 127.33 mK (0.93 mK below the trimer ground state), respectively. Precisely the same shape of the short-range correlation (r_ij < 4 \AA) in the dimer appear in the ground and excited states of the trimer and tetramer. Analyzing the asymptotic wave functions (accurate up to 1000 \AA) of those excited states, we propose a model which predicts the binding energy of the first excited state of 4He_N measured from the 4He_{N-1} ground state to be N/2(N-1)xB_2 using dimer binding energy B_2 only; fit in N=3 and 4 is excellent.
    Few-Body Systems 11/2011; 54(7-10). DOI:10.1103/PhysRevA.85.022502 · 1.51 Impact Factor
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    ABSTRACT: Recent studies on breakup reactions with the continuum-discretized coupled-channels method are reviewed. The topics covered are: four-body breakup processes for 6He induced reaction, dynamical relativistic effects on Coulomb breakup, microscopic description of projectile breakup processes, description of ternary processes (new triple-α reaction rate) and new approach to inclusive breakup processes.
    Journal of Physics Conference Series 09/2011; 312(8):082008. DOI:10.1088/1742-6596/312/8/082008
  • M Kamimura
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    ABSTRACT: Predictive power of theory needs good models and accurate calculation methods to solve the Shrödinger equations of the systems concerned. In this talk, I present some examples of successful predictions based on the nuclear cluster models of light nuclei and hypernuclei and on the calculation methods (CDCC and GEM) that have been developed by Kyushu group.
    Journal of Physics Conference Series 09/2011; 321(1):012010. DOI:10.1088/1742-6596/321/1/012010
  • Masayasu Kamimura
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    ABSTRACT: Predictive power of theory needs good models and accurate calculation methods to solve the Shrödinger equations of the systems concerned. We present some examples of successful predictions based on the nuclear cluster models of light nuclei and hypernuclei and on the calculation methods that have been developed by Kyushu group.
    05/2011; 1355(1):69-76. DOI:10.1063/1.3584047
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    ABSTRACT: Triple‐α reaction rate is re‐evaluated by directly solving the three‐body Schrödinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum‐discretized coupled‐channels method for three‐body scattering. An accurate description of the α‐α nonresonant states significantly quenches the Coulomb barrier between the first two α‐particles and the third α‐particle. Consequently, theα‐α nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomoto’s method for three‐body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three‐body model calculation. We find an increase in triple‐α reaction rate by about 20 orders of magnitude around 10 7 K compared with the rate of NACRE.
    THE 10TH INTERNATIONAL SYMPOSIUM ON ORIGIN OF MATTER AND EVOLUTION OF GALAXIES: OMEG—2010; 08/2010
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    E Hiyama · M. Kamimura · Y Yamamoto · T. Motoba
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    ABSTRACT: Energy levels of the double $\Lambda$ hypernucleus, $^{11}_{\Lambda \Lambda}$Be are calculated within the framework of an $\alpha \alpha n \Lambda \Lambda$ five-body model. Interactions between constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the $\alpha \alpha$, $\alpha \alpha n$ nuclei and the existing data for $\Lambda$-binding energies of the $\alpha \Lambda$, $\alpha \alpha \Lambda$, $\alpha n \Lambda$ and $\alpha \alpha n \Lambda$ systems. An effective $\Lambda \Lambda$ interaction is constructed so as to reproduce, within the $\alpha \Lambda \Lambda$ three-body model, the $B_{\Lambda \Lambda}$ of $^6_{\Lambda \Lambda}$He, which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the $\alpha \alpha n \Lambda \Lambda$ system, $B_{\Lambda \Lambda}$ of the ground and bound excited states of $^{11}_{\Lambda \Lambda}$Be are calculated with the Gaussian Expansion Method. The Hida event, recently observed at KEK-E373 experiment, is interpreted as an observation of the ground state of the $^{11}_{\Lambda \Lambda}$Be. Comment: 4pages, 3 figures
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    ABSTRACT: Triple‐α reaction rate is re‐evaluated by directly solving the three‐body Schrödinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum‐discretized coupled‐channels method for three‐body scattering. An accurate description of the α‐α nonresonant states significantly quenches the Coulomb barrier between the first two α‐particles and the third α‐particle. Consequently, the α‐α nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomoto’s method for three‐body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three‐body model calculation. We find an increase in triple‐α reaction rate by 26 orders of magnitude around 10 7 K compared with the rate of NACRE.
    TOURS SYMPOSIUM ON NUCLEAR PHYSICS AND ASTROPHYSICS—VII; 06/2010
  • Masayasu Kamimura · Yasushi Kino · Emiko Hiyama
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    ABSTRACT: We study the new type of big‐bang nucleosynthesis (BBN) reactions that are catalyzed by a hypothetical long‐lived negatively charged, massive leptonic particle (called X−) such as the supersymmetric (SUSY) particle stau, the scalar partner of the tau lepton. It is known that if the X− particle has a lifetime of τX≳103 s, it can capture a light element previously synthesized in standard BBN and form a Coulombic bound state and induces various types of reactions in which X− acts as a catalyst. Some of these X− catalyzed reactions have significantly large cross sections so that the inclusion of the reactions into the BBN network calculation can markedly change the abundances of some elements. We use a high‐accuracy three‐body calculation method developed by the authors and provide precise cross sections and rates of these catalyzed BBN reactions for use in the BBN network calculation.
    05/2010; 1238(1):139-144. DOI:10.1063/1.3455917

Publication Stats

4k Citations
341.40 Total Impact Points

Institutions

  • 2008–2013
    • RIKEN
      • Nishina Center for Accelerator-Based Science (RNC)
      Вако, Saitama, Japan
  • 1982–2013
    • Kyushu University
      • Department of Physics
      Hukuoka, Fukuoka, Japan
    • Hosei University
      Edo, Tōkyō, Japan
  • 2000–2009
    • Fukuoka University
      Hukuoka, Fukuoka, Japan
  • 2004
    • University of the Ryukyus
      • Department of Physics and Earth Sciences
      Okinawa, Okinawa, Japan
  • 1998–2004
    • Kanto Gakuin University
      Kawasaki Si, Kanagawa, Japan
    • University of Surrey
      • Department of Physics
      Guildford, ENG, United Kingdom
  • 2001
    • High Energy Accelerator Research Organization
      Tsukuba, Ibaraki, Japan
    • Hokkaido University
      • Division of Physics
      Sapporo, Hokkaidō, Japan
  • 1991
    • Shimonoseki City University
      Simonoseki, Yamaguchi, Japan
  • 1989
    • Chiba Keizai University
      Tiba, Chiba, Japan