Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session KE: Mini-symposium on Pair and Cluster Correlations in Nuclei II |
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Sponsoring Units: DNP JPS Chair: Hiashi Horiuchi, Kyoto University Room: Ritz-Carlton Hotel Amphitheater |
Thursday, September 22, 2005 2:00PM - 2:30PM |
KE.00001: Systematic analyses on Hydrogen isotopes by using an extended AMD approach Invited Speaker: It is a very challenging problem to make an extremely neutron-excess system which corresponds to the neutron star. Very recently, an experimental evidence of $^7$H was reported as an enhancement of the cross section above the t+$n$+$n$+$n$+$n$ threshold [1]. Its neutron ratio to the proton is the largest value of six. It is very interesting to investigate pair correlations between the nucleons and the cluster-like correlation of triton in such the almost neutron matter like nuclei only with one proton. Recently, we propose a new extended AMD approach [2]. In this approach, AMD combined with the generator coordinate method is extended with the idea of the stochastic variational method (SVM). We call this new approach AMD triple-S (Superposition of Selected Snapshots) [2]. By using AMD triple-S, we will give the calculated results and discussions for H-isotopes with the core-nucleus plus the valence neutrons model, and discuss the nucleon correlations in the extremely neutron-rich nuclei. Work done in collaboration with Naoyuki Itagaki, Niigata University. \newline \newline [1] A.A. Korsheninnikov $et$ $al.$, Phys. Rev. Lett. {\bf90}, 082501 (2003). \newline [2] N. Itagaki, A. Kobayakawa and S. Aoyama, Phys. Rev. {\bf C68}, 054302 (2003). [Preview Abstract] |
Thursday, September 22, 2005 2:30PM - 2:45PM |
KE.00002: $0_^+ $ states of the ${ }^{12}$C nucleus: Faddeev calculation in configurations space Branislav Vlahovic, Igor Filikhin, Vladimir Suslov The $\alpha $-cluster model and Faddeev equations in configuration space are applied to study the ${ }^{12}$C nucleus. The model includes the Ali-Bodmer nuclear potential [1], attractive three-body potential, and takes into account the Coulomb interaction. An s-wave model [2] is adapted and parameters of the three-body potential are chosen to describe the first two 0$_^+ $ levels of ${ }^{12}$C. The value of the range parameter of the potential is adjusted to reproduce the position of diffraction minimum for the elastic form factor of ${ }^{12}$C. The model assumes a strong distortion of the charge density of $\alpha $ clusters inside the ${ }^{12}$C nucleus. It was found that the most probable configuration of the $\alpha $-clusters in the 0$_1^+ $state corresponds to an equilateral triangle with sides as large as 3.5 fm and in the 0$_2^+ $ state to a linear chain with the values of 2.9 fm and 13.1 fm for each link. Having calculated low-lying levels of ${ }^{12}$C, we found that the contributions of higher partial waves of nuclear interaction to the energy of 3$\alpha $-system are unnaturally large and some states turn to be overbound. Upon applying the method [3] based on the Pade approximation we got satisfactory description for the 0$_3^+ $ and 0$_4^+ $ states [4]. Additional $0^+$ broad resonance obtained in [3] was not found. 1. S. Ali, A. R. Bodmer, Nucl. Phys. 80, 99 (1966). 2. Z. Papp, et al. Few-Body Systems 30, 31 (2001). 3. C. Kurokawa and K. Kato, Phys. Rev. C76, 021301-1 (2005). 4. http://www.tunl.duke.edu/nucldata/. [Preview Abstract] |
Thursday, September 22, 2005 2:45PM - 3:00PM |
KE.00003: Formation and Dissolution of the $\alpha +^{16}$O Cluster Core and their relation to the Motion of the Valance Neutrons in Ne Isotopes Masaaki Kimura Focusing on the $\alpha $ clustering, the level structure of Ne isotopes will be discussed. The theoretical framework of the antisymmetrized molecular dynamics (AMD) plus generator coordinate method with the Gogny D1S interaction. The formation and dissolution of $\alpha +^{16}$O cluster core which strongly depend on the motion of the valance neutrons are discussed. The presence of the molecular-orbital bands in $^{21} $Ne and $^{22}$Ne which have an $\alpha +^{16}$O cluster core surrounded by valance neutrons occupying the molecular-orbitals are presented. The a+$^{18}$O molecular bands of $^{22}$Ne is also discussed. The presense of the molecule-like structure which has an $\alpha +^{16}$O cluster core plus valance neutrons are suggested throughout the Ne isotopes and their properties and dependence on the nutron number will be discussed. [Preview Abstract] |
Thursday, September 22, 2005 3:00PM - 3:15PM |
KE.00004: Staying probability of valence neutron around each clusters Tooru Yoshida, Naoyuki Itagaki, Takaharu Otsuka It has been shown that there are many states in light nuclei which have alpha cluster components, for example in Be isotopes and in C isotopes. If we calculate larger system like Ne isotopes, shell model configuration also become more important. Therefore we need to superpose many Antisymmetrized Molecular Dynamics (AMD) basis to describe such nuclei. The AMD Triple-S is such kind of method. Based on this method we confirm existence of alpha correlation. We take variety of configuration of the core, for example very developed cluster structure. We see to what extent these configurations are realized. Afterward we restrict the distance between clusters and show the change of single-particle motion of valence neutrons as a function of the distance. Here we take notice of staying probability of valence neutrons around each clusters of the core. We define the probability properly, and we can see that the behavior is quite different between in positive parity states and in negative parity states. [Preview Abstract] |
Thursday, September 22, 2005 3:15PM - 3:30PM |
KE.00005: Coexistence of Cluster Structure and Mean-field-type Structure in Medium-weight Nuclei Yasutaka Taniguchi, Masaaki Kimura, Hisashi Horiuchi We have studied the coexistence of cluster structure and mean-field-type structure in $^{40}$Ca using Antisymmetrized Molecular Dynamics (AMD) with a new type of constraint of clustering for AMD, which we proposed. The constraint is for the distance between the centers of masses of groups of nucleons corresponded to clusters. By energy variation with the constraint and quadrupole deformation constraint, we calculated wave functions of many kinds of cluster structure, for example $\alpha$-$^{36}$Ar, $^{12}$C-$^{28}$Si and so on, and mean-field-type structure. Superposing these wave functions, we performed GCM calculation. We found that $\alpha$-$^{36}$Ar cluster structure and $^{12}$C-$^{28}$Si cluster structure were important components for $K = 0_2^+$ and $0_3^+$ bands, respectively. We also discuss negative parity states of $^{40}$Ca. [Preview Abstract] |
Thursday, September 22, 2005 3:30PM - 3:45PM |
KE.00006: A new stochastic method superposing multiple Slater determinants Kazuhiro Yabana, Satoshi Shinohara, Hirofumi Ohta, Takashi Nakatsukasa In light nuclei, there appear various excited states with different correlation structures. We propose a new stochastic method of superposing multiple Slater determinants which we wish to describe these excited states in a unified way. Our method starts with preparing a lot of Slater determinants whose single-particle orbitals are randomly distributed Gaussian wave packets. They are cooled towards a mean-field solution by the imaginary-time method. In the course of cooling, a lot of shoulder states as well as local minima appear. They exhibit various correlation structures with clustering, deformations, and so on. We store these configurations and then make a configuration mixing calculation with projections with respect to the parity and the angular momentum. To examine usefulness and feasibility of the method, we made a calculation for $^{16} $O nucleus employing a simple BKN interaction. We find that our method provides convergent solutions for a few excited states for each spin and parity. [Preview Abstract] |
Thursday, September 22, 2005 3:45PM - 4:00PM |
KE.00007: Projected Skyrme Hartree-Fock approach to structure of Mg isotopes Hirofumi Ohta, Takashi Nakatsukasa, Kazuhiro Yabana Skyrme-Hartree-Fock (SHF) calculations using the Cartesian mesh representation has been successful to describe ground-state properties of nuclei for a wide mass region. We extend the method so as to describe odd-parity excited configurations in the variation after parity projection (H.~Ohta, K.~Yabana, and T.~Nakatsukasa, Phys. Rev. C {\bf 70} (2004) 014301). The angular momentum projection in the full three-dimensional Euler angles has been performed for the first time in realistic calculations. Now the method is being applied to Mg isotopes. The ground-state correlation energies, excitation spectra, transition amplitudes, etc. are calculated. The calculation shows an importance of symmetry restoration. [Preview Abstract] |
Thursday, September 22, 2005 4:00PM - 4:15PM |
KE.00008: Cluster structure and excitation strengths in $^{11}$B T. Kawabata, H. Akimune, Y. Fujita, H. Fujita, M. Fujiwara, K. Hara, K. Hatanaka, M. Itoh, K. Nakanishi, Y. Shimbara, A. Tamii, M. Uchida, H.P. Yoshida, M. Yosoi, Y. Kanada-E'nyo, S. Kishi, H. Sakaguchi, S. Terashima, Y. Yasuda, T. Wakasa The $^{11}$B($^3$He$,t$), $^{11}$B($d,d'$), and $^{11}$B($p,p'$) reactions were measured at forward scattering including zero degrees. Combining the experimental results from the three reactions, the isoscalar and isovector spin-flip M1 strengths were successfully determined for the low-lying states in $^{11}$B. The proton and neutron quadrupole excitation strengths were also deduced from the $^{11}$B($d,d'$) results and previously measured $\gamma$- decay widths. The obtained excitation strengths were compared with the shell model and antisymmetrized molecular dynamics calculations. It was found that the $3/2^-_3$ state in $^{11}$B has a cluster structure. This state is considered to be an analog state of the $0^+_2$ state in $^{12}$C which is a well-known $3\alpha$ cluster state. For the $5/2^-_3$ state, both the shell-model-like and cluster-like structures were observed. [Preview Abstract] |
Thursday, September 22, 2005 4:15PM - 4:30PM |
KE.00009: Cluster structure in A=6 nuclei above particle decay threshold Hidetoshi Akimune, Tamio Yamagata, Maki Kinoshita, Masahisa Ohta, Ayako Shiokawa, Hiroaki Utsunomiya, Kaoru Hara, Shintaro Nakayama, Kenichi Fushimi, Kayoko Ichihara, Yuko Matsui, Mamoru Fujiwara, Naonobu Hashimoto, Keigo Kawase, Kousuke Nakanishi, Masaru Yosoi, Masayoshi Tanaka, Mark Greenfield, Keigo Hara The di-trinucleon clustering-resonance of $^{3}$He+$^{3}$He in $^{6}$Be and t+t in $^{6}$He were studied via the $^{6}$Li($^{3}$He,t $^{3}$He) and $^{6}$Li($^{7}$Li,$^{7}$Be t) reactions at the incident energies of 150 MeV/A and 65 MeV/A. A new resonance in $^{6}$Be and $^{6}$He was found at around Ex=18 MeV in the binary decay channel of $^{3}$He+$^{3}$He and t+t. The angular correlations measured for $^{3}$He and t particles in the binary decay show a contribution dominantly from the multipolarity of an L=1. [Preview Abstract] |
Thursday, September 22, 2005 4:30PM - 4:45PM |
KE.00010: Alpha Condensed Structure of Resonance States of 12C Yasuro Funaki, Akihiro Tohsaki, Hisashi Horiuchi, Peter Schuck, Gerd Roepke The states with $J^\pi=0^+$, $2^+$, and $4^+$ of $^{12}$C with excitation energies less than about 15 MeV are investigated with the alpha condensate wave function with spatial deformation and by using the method of ACCC (analytic continuation in the coupling constant) which is necessary for a proper treatment of resonance states. The calculated energy and width of the recently observed $2_2^+$ state are found to be well reproduced. The obtained $2_2^+$ wave function has a large overlap with a single condensate wave function of $3\alpha$ gas-like structure. The density distribution is shown to be almost the same as that of the $0_2^+$ state that is regarded as a $3\alpha$ Bose- condensed state, if the energy of the $2_2^+$ state is scaled down to the same value as the one of the $0_2^+$ state. Furthermore, the kinetic energy, nuclear interaction energy, and Coulomb interaction energy of the calculated $2_2^+$ state are shown to be very similar to those of the $0_2^+$ state. It is also shown that the $2_2^+$ state is obtained by promoting just one alpha cluster out of the condensate of the $0_2^+$ state into a $D$-wave. We conclude that the $2_2^+$ state has a structure similar to the $0_2^+$ state of Bose-condensate character with a dilute $3\alpha$ gas-like structure$[1]$.\\ $[$1$]$ Y. Funaki, A. Tohsaki, H. Horuichi, P. Schuck, and G. R\"opke, Euro. Phys. J. A, Vol. 24, No. 3 (2005), pp. 321 - 344. [Preview Abstract] |
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