M. Kamimura

Kyushu University, Hukuoka, Fukuoka, Japan

Are you M. Kamimura?

Claim your profile

Publications (167)319.3 Total impact

  • Source
    E. Hiyama, M. Kamimura
    [Show abstract] [Hide abstract]
    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.
    09/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The structure of heavy hyperhydrogen 6ΛH is studied within the framework of a tnnΛtnnΛ 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,tΛtn,tΛ and tnn subsystems. As long as we reproduce the energy and width of 5H within the error bar, the ground state of 6ΛH is obtained as a resonant state.
    Nuclear Physics A 06/2013; 908:29–39. · 2.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Progress of Theoretical and Experimental Physics. 02/2013; 2013(7).
  • Source
    E. Hiyama, M. Kamimura
    [Show abstract] [Hide abstract]
    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). · 3.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    02/2012;
  • [Show abstract] [Hide abstract]
    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). · 1.11 Impact Factor
  • Source
    E. Hiyama, M. Kamimura
    [Show abstract] [Hide abstract]
    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). · 1.05 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
  • M Kamimura
    [Show abstract] [Hide abstract]
    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.
  • Source
    E Hiyama, M. Kamimura, Y Yamamoto, T. Motoba
    [Show abstract] [Hide abstract]
    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
    06/2010;
  • Masayasu Kamimura, Yasushi Kino, Emiko Hiyama
    [Show abstract] [Hide abstract]
    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.
    AIP Conference Proceedings. 05/2010; 1238(1):139-144.
  • Source
    E Hiyama, M Kamimura, Y Yamamoto, T Motoba
    [Show abstract] [Hide abstract]
    ABSTRACT: Energy levels of the double Λ hypernucleus (ΛΛ)(11)Be are calculated within the framework of a ααnΛΛ five-body model. Interactions between constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the αα, ααn nuclei and the existing data for Λ-binding energies of the αΛ, ααΛ, αnΛ, and ααnΛ systems. An effective ΛΛ interaction is constructed so as to reproduce, within the αΛΛ three-body model, the B(ΛΛ) of (ΛΛ)(6)He, which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the ααnΛΛ system, B(ΛΛ) of the ground and bound excited states of (ΛΛ)(11)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 (ΛΛ)(11)Be.
    Physical Review Letters 05/2010; 104(21):212502. · 7.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The method of continuum-discretized coupled-channels (CDCC) is applied to two nuclear astrophysics studies. One is the determination of the astrophysical factor S17(0) for the 7Be(p,gamma)8B reaction from the analysis of 8B breakup by 208Pb at 52 A MeV. We obtain S17(0) = 20.9-1.9+2.0 eV b, which is significantly larger than the previous one, S17(0) = 18.9+/-1.8 eV b, determined from an analysis with the virtual photon theory. The difference between the two values is found to be due to the contributions from nuclear breakup and higher-order processes. The other application of CDCC is the re-evaluation of the triple-alpha reaction rate by directly solving the three-body Schrödinger equation. The resonant and nonresonant processes are treated on the same footing. An accurate description of the alpha-alpha nonresonant states significantly quenches the Coulomb barrier between the first two alpha-particles and the third alpha-particle. Consequently, the alpha-alpha nonresonant continuum states give a markedly larger contribution at low temperatures than that reported in previous studies. We find an increase in triple-alpha reaction rate by 26 orders of magnitude around 107 K compared with the rate of NACRE.
    05/2010;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The structure of light hypernuclei with strangeness S = -2 is investigated with the three-, four-, and five-body cluster model and the Gaussian Expansion method (GEM). Energy levels of the double-Lambda hypernuclei (7_{Lambda) Lambda}He, (7_{Lambda) Lambda}Li, (8_{Lambda) Lambda}Li, (9_{Lambda) Lambda}Li, (9_{Lambda) Lambda}Be, and (10) _{Lambda Lambda}Be are predicted with the framework of alpha Lambda Lambda four-body model, where x = n, p, d, t, (3) He, and alpha, respectively. Also, energy levels of the double Lambda hypernucleus, (11) _{Lambda Lambda}Be are calculated within the framework of a alpha alpha nLambda Lambda five-body model. The Demachi-Yanagi event, identified as (10) _{Lambda Lambda}Be, is interpreted as an observation of its 2(+) state excited state. The Hida event, recently observed at KEK-E373 experiment, is interpreted as an observation of the ground state of the (11) _{Lambda Lambda}Be. Detail ed structure calculations in (12}_{Xi(-)) Be, (5}_{Xi(-)) H, (9}_{Xi(-)) Li, (7}_{Xi(-)) H and (\:10}_{Xi(-)) Li are performed within the framework of the microscopic two-, three- and four-body cluster models. (7}_{Xi(-)) H and (10}_{Xi(-)) Li are predicted to have bound states.
    Progress of Theoretical Physics Supplement 01/2010; 185:152-196. · 1.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The structure of light hypernuclei with strangeness S = -1 is investigated with the three- and four-body cluster model and the Gaussian Expansion method (GEM). Interesting phenomena such as shrinkage effect of the core nucleus and the halo and skin structure due to the glue-like role of Lambda particle are demonstrated from the study of structure of (6_{Lambda}) He, (7_{Lambda}) Li and (13}_{Lambda) C. Precise three- and four-body cluster calculation of (7_{Lambda}) He, (7_{Lambda}) Li, (7_{Lambda}) Be, (9_{Lambda}) Be and (13}_{Lambda) C provide us with information about Lambda N interaction such as spin-spin, spin-orbit, charge symmetry breaking term, etc., by comparing with the recent experimental data. Precise four-body calculation taking NNNLambda and NNNSigma for (4_{Lambda}) H and (4_{Lambda}) He are performed and the role of Lambda-Sigma conversion and the size of the virtual Sigma component in (4_{Lambda}) H and (4_{Lambda}) He are discussed.
    Progress of Theoretical Physics Supplement 01/2010; 185:106-151. · 1.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The structure of the T=1 isotriplet hypernuclei, {sub }He, {sub }Li, and {sub }Be within the framework of an ++N+N four-body cluster model is studied. Interactions between the constituent subunits are determined so as to reproduce reasonably well the observed low-energy properties of the N, , NN, and N subsystems. Furthermore, the two-body N interaction is adjusted so as to reproduce the 0{sup +}-1{sup +} splitting of {sub }H. Also, a phenomenological N charge symmetry breaking (CSB) interaction is introduced. The binding energy of the ground state in {sub }He is predicted to be 5.16(5.36) MeV with (without) the CSB interaction. The calculated energy splittings of the 3/2{sup +}-5/2{sup +} states in {sub }He and {sub }Li are around 0.1 MeV. We point out that there is a three-layer structure of the matter distribution, particle, skin, and proton or neutron halo, in the {sub }He(J=5/2{sup +}), {sub }Li(J=5/2{sup +}), and {sub }Be(J=1/2{sup +}) states.
    Physical Review C 11/2009; 80(5):054321-054321. · 3.72 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, in KEK-E373 experiment, new double lambda hypernucleus, 'hida' event, ^11lambdalambdaBe was reported. This observation is important to get information on lambdalambda interaction. For study of stucture of this lambda hypernucleus, we perform five-body calculation of alpha+alpha+n+lambda+lambda model. In this symposium, the level structure of this hypernucleus will be discussed.
    10/2009;
  • Source
    Kazuyuki Ogata, Masataka Kan, Masayasu Kamimura
    [Show abstract] [Hide abstract]
    ABSTRACT: The triple-\alpha reaction rate is re-evaluated by directly solving the three-body Schr\"odinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. Accurate description of the \alpha-\alpha nonresonant states significantly quenches the Coulomb barrier between the two-\alpha's and the third \alpha particle. Consequently, the \alpha-\alpha nonresonant continuum states below the resonance at 92.04 keV, i.e., the ground state of 8Be, give markedly larger contribution at low temperatures than in foregoing 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 about 20 orders-of-magnitude enhancement of the triple-\alpha reaction rate around 10^7 K compared to the rate of NACRE. Comment: To be published in Prog. Theor. Phys. Vol.121, No.4. More detailed description of numerical inputs, further discussion in relation to Nomoto's method (NACRE), new typeset using PTP TeX
    Progress of Theoretical Physics 05/2009; · 2.48 Impact Factor
  • Source
    Yasushi Kino, Masayasu Kamimura, Emiko Hiyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Synopsis Calculations of low energy atomic collision are performed for the new types of big-bang nucleosynthesis (BBN) reactions that are enhanced by a supersymmetric (SUSY) particle stau, a scalar partner of the tau lepton. If a stau has a lifetime > 10 3 s, it would capture a light element previously synthesized in standard BBN and form a Coulombic bound state. The bound state, an exotic atom, is expected to induce various nuclear reactions as in the muon catalyzed fusion. A negatively charged stau works as a catalyzer. We use a few-body calculational method developed by the authors, and provide precise cross sections and rates of the stau-catalyzed BBN reactions for the BBN network calculation. A gravitino is the lightest supersymmetry particle (LSP), and it can be a candidate of cold dark matter in the universe. The next LSP is a charged scalar lepton (X) which is most likely the stau (! !) [1]. The mass of the particle X – is assumed to be 100 GeV/c 2 which is two orders of magnitude larger than a proton mass (0.9 GeV/c 2). The lifetime of the X – is considered to be more than 10 3 s. The X – is a point-like particle and interacts with matter via Coulomb interaction only. It can be regarded as a heavy electron. If it decays after the big-bang nucleosynthesis (BBN), the X – can form bound states together with positively charged nuclei as an exotic atom/molecule, which leads to an enhancement of some nuclear reaction rates. That is, X – plays as a catalyzer of nuclear fusion (catalyzed BBN or CBBN in short) and affects cosmological nuclear abundances. Recently, Pospelov pointed out that the reaction cross section of 6 Li production in the stau atomic collision (!X " + d # 6 Li + X ") was enhanced by eight orders of magnitude as compared with the reaction in the standard BBN process [2]. In his calculation, however, the estimation of the cross section was based on a simple scaling procedure, and he paid no attention to the low energy atomic collision theory that played an essential role in the reaction in which the α-particle transferred from the αX – atom to the deuteron. Since the binding energy of the αX – is 337 keV and the collision energy (10~100 keV) in the first several minutes after the big-bang, the stau atomic collision must be regarded as the low energy atomic collision which is dominated by the Coulombic interaction. Recent literature papers (reviewed in Refs. [3,4]) have claimed that some of these stau-catalyzed reactions have significantly large cross sections so that inclusion of the reactions into the BBN network calculation can change drastically abundances of some elements, giving not only a solution to the 6 Li-7 Li problem (calculated underproduction of 6 Li by 1000 times and overproduction of 7 Li+ 7 Be by three times) but also a constraint on the lifetime and the primordial abundance of the elementary particle stau. However, most of these literature calculations of the reaction cross sections were made assuming too naive models or approximations that were unsuitable for those complicated low-energy atomic collisions. We precisely calculate the nuclear reactions induced by stau atomic collisions and provide reaction cross sections for the BBN network calculations [5,6]. The results are consistent with the current prediction of the SUSY theory. The adopted theoretical method and numerical technique (reviewed in Ref. [7]) have been developed by the present authors, and have been successfully applied in the field of few-body systems.
    Journal of Physics Conference Series 01/2009; 194(7).
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present analyses of breakup effects of 6He on the elastic scattering by the continuum-discretized coupled-channels method, in which the reaction system is described as a four-body model, n+n+4He+target. In this analysis, three-body breakup continuum of 6He is discretized by daiagonalizing the internal Hamiltonian of 6He in a space spanned by the Gaussian basis functions. The calculated elastic cross sections are in good agreement with the experimental data, which shows that nuclear and Coulomb breakup effects are significant.
    International Journal of Modern Physics A 01/2009; 24(11):2191-2197. · 1.13 Impact Factor

Publication Stats

3k Citations
319.30 Total Impact Points

Institutions

  • 1984–2013
    • Kyushu University
      • Department of Physics
      Hukuoka, Fukuoka, Japan
  • 2000–2011
    • RIKEN
      Вако, Saitama, Japan
  • 2000–2009
    • Fukuoka University
      Hukuoka, Fukuoka, Japan
  • 2006
    • Nara Women's University
      • Department of Physics
      Ibaraki, Osaka-fu, Japan
  • 1998–2004
    • Tsuru University
      Yokohama, Kanagawa, Japan
  • 2003
    • The University of Tokyo
      • Department of Physics
      Edo, Tōkyō, Japan
  • 1998–2003
    • Tohoku University
      • Department of Chemistry
      Japan
  • 2001
    • Osaka City University
      Ōsaka, Ōsaka, Japan
  • 1989–1998
    • University of Surrey
      • Department of Physics
      Guildford, ENG, United Kingdom
  • 1982–1991
    • Shimonoseki City University
      Simonoseki, Yamaguchi, Japan
  • 1988
    • Osaka University
      • Laboratory of Nuclear Studies
      Suita, Osaka-fu, Japan
  • 1985–1988
    • Hosei University
      • Faculty of Computer and Information Sciences
      Edo, Tōkyō, Japan
  • 1987
    • University of Pittsburgh
      Pittsburgh, Pennsylvania, United States