1 / 37

Structure of L hypernuclei with the antisymmetrized molecular dynamics method

Structure of L hypernuclei with the antisymmetrized molecular dynamics method. Masahiro Isaka (RIKEN). Grand challenges of hypernuclear physics. 2 body interaction between baryons (nucleon, hyperon) hyperon-nucleon (YN) hyperon-hyperon (YY)

vera
Download Presentation

Structure of L hypernuclei with the antisymmetrized molecular dynamics method

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Structure of Lhypernuclei with the antisymmetrized molecular dynamics method Masahiro Isaka (RIKEN)

  2. Grand challenges of hypernuclear physics • 2 body interaction between baryons (nucleon, hyperon) • hyperon-nucleon (YN) • hyperon-hyperon (YY) • Addition of hyperon(s) shows us new features of nuclear structure Ex.) Structure change by hyperon(s) • No Pauli exclusion between N and Y • YN interaction is different from NN Interaction: To understand baryon-baryon interaction + A major issue in hypernuclear physics Normal nucleus As an impurity L hypernucleus Structure: To understand many-body systemof nucleons and hyperon “Hyperon as an impurity in nuclei” Today’s talk: “Structure change by a L particle”

  3. Recent achievements in (hyper)nuclear physics Knowledge of LN interaction • Study of light (s, p-shell) L hypernuclei • Accurate solution of few-body problems [1] • LN G-matrix effective interactions [2] • Increases of experimental information [3] Development of theoretical models • Through the study of unstable nuclei Ex.: Antisymmetrized Molecular Dynamics (AMD)[4] • AMD can describe dynamical changes of various structure • No assumption on clustering and deformation Recent developments enable us to study structure of L hypernuclei [1] E. Hiyama, NPA 805 (2008), 190c, [2] Y. Yamamoto, et al., PTP Suppl. 117 (1994), 361., [3] O. Hashimoto and H. Tamura, PPNP 57 (2006), 564., [4] Y. Kanada-En’yoet al., PTP 93 (1995), 115.

  4. Structure of L hypernuclei L hypernuclei observed so far • Concentrated in light L hypernuclei • Most of them have well pronounced cluster structure Developed cluster Light L hypernuclei Taken from O. Hashimoto and H. Tamura, PPNP 57(2006),564.

  5. Structure of L hypernuclei L hypernuclei observed so far • Concentrated in light L hypernuclei • Most of them have well pronounced cluster structure Changes of cluster structure 6Li 7 Li 7 Li Example: L L Adding L T. Motoba, et al., PTP 70,189 (1983) E. Hiyama, et al., PRC 59 (1999), 2351. K. Tanida, et al., PRL86 (2001), 1982. Developed cluster Light L hypernuclei d a L reduces inter-cluster distance between a + d Taken from O. Hashimoto and H. Tamura, PPNP 57(2006),564.

  6. Toward heavier and exotic L hypernuclei Experiments at J-PARC, JLab and Mainz etc. • Heavier and neutron-richL hypernuclei can be produced • Various structures will appear in hypernuclei sdshell nuclei p-sd shell region Ex.: 21LNe Coexistence of structures Developed cluster n-rich nuclei Light L hypernuclei Ex.: 12LBe n-rich region Exotic cluster Taken from O. Hashimoto and H. Tamura, PPNP 57(2006),564.

  7. Stricture ofp-sd shell nuclei • Mean-field like and a + 16O cluster structures coexist within the small excitation energy Ex.) 20Ne 20Ne a + 16O Mean-field 6Li 7LLi Adding L cf.7LLi (a + d + L) 2- d a 0+(g.s.) Mean-field structure also contributes L reduces the a + d distance 1- What is difference in structure changes by adding a L particle ?

  8. Structure of neutron-rich nuclei • Exotic cluster structure exists in the ground state regions “molecular-orbit” Ex.) Be isotopes • Be isotopes have a 2a cluster structure Y. Kanada-En’yo, et al., PRC60, 064304(1999) N. Itagaki, et al., PRC62 034301, (2000). • 2a cluster structure is changed depending on the neutron number p2config. s2config. s-orbit psconfig. psconfig. p-orbit What is happen by adding a L to these exotic cluster structure ?

  9. L Hypernucleichart will be extended “Structure of L hypernuclei” How does a L particle modify structures of p-sd shell/n-rich nuclei ? sdshell nuclei p-sd shell region Ex.: 21LNe Coexistence of structures Developed cluster n-rich nuclei Light L hypernuclei Ex.: 12LBe n-rich region Exotic cluster Our method: antisymmetrized molecular dynamics (AMD) Hypernuclear chart: O. Hashimoto and H. Tamura, PPNP 57(2006),564.

  10. Theoretical Framework: HyperAMD M.Isaka, et al., PRC83(2011) 044323 M. Isaka, et al., PRC83(2011) 054304 We extended the AMD to hypernuclei HyperAMD (Antisymmetrized Molecular Dynamics for hypernuclei) • Hamiltonian NN:Gogny D1S LN:YNG interactions (NF, NSC97f) • Wave function • Nucleon part:Slater determinant • Spatial part of single particle w.f. is • described as Gaussian packet • Single-particle w.f. of Lhyperon: • Superposition of Gaussian packets • Total w.f.:

  11. Theoretical Framework: HyperAMD M.Isaka, et al., PRC83(2011) 044323 M. Isaka, et al., PRC83(2011) 054304 • Procedure of the calculation • Variational Calculation • Imaginary time development method • Variational parameters: L Initial w.f.: randomly generated L L Energy variation Various deformations and/or cluster structure

  12. Theoretical Framework: HyperAMD M.Isaka, et al., PRC83(2011) 044323 M. Isaka, et al., PRC83(2011) 054304 • Procedure of the calculation • Variational Calculation • Imaginary time development method • Variational parameters: Angular Momentum Projection • Generator Coordinate Method(GCM) • Superposition of the w.f. with different configuration • Diagonalization of and

  13. 1. Heavier (sd-shell) L hypernuclei What is the difference of structure changes ? Examples: 21LNe (Theoretical prediction) Mean field like state a + 16O cluster state Based on M. Isaka, M. Kimura, A. Dote, and A. Ohnishi, PRC83, 054304(2011)

  14. Stricture ofp-sd shell nuclei • Mean-field like and a + 16O cluster structures coexist within the small excitation energy Ex.) 20Ne 20Ne a + 16O Mean-field Mean-field 0+(g.s.) 2- 1- What is difference in structure changes by adding a L particle ?

  15. “Shrinkage effect” of cluster structure by L • 6Li: a+ d cluster structure • L hyperon penetrates into the nuclear interior • L hyperon reducesa+ d distance Shrinkage effect: L hyperon makes nucleus compact T. Motoba, et al., PTP 70,189 (1983) E. Hiyama, et al., PRC 59 (1999), 2351. K. Tanida, et al., PRL86 (2001), 1982. 7 Example: LLi B(E2) reduction (Observable) Adding L +0.5 B(E2) = 3.6±0.5 e2fm4 +0.4 d a B(E2) = 10.9±0.9 e2fm4

  16. Structure of 20Ne • Various structure coexist near the ground state 20Ne(AMD) Kp=0-band (a + 16Oclustering) Ground band (mean-field like) 0+(g.s.) What is difference in structure change between two bands? Difference in shrinkage effects? 1-

  17. Preceding Study of 21LNe: cluster model calculation • Structure study of 21LNe hypernucleus • a + 16O + Lcluster model • “shrinkage effect” by L Lreduce the RMS radii in both ground and Kp = 0+ bands T. Yamada, K. Ikeda, H. Bandō and T. Motoba, Prog. Theor. Phys. 71 (1984), 985. MeV Similar B(E2) reduction in both bands (Both 20 % reduction)

  18. Results: Excitation spectra of 21LNe • Energy Spectra of 21LNe a+Ocluster Mean-field like Mean-field like a+Ocluster a+17LOthreshold a+16O threshold 20Ne (AMD) 21LNe (AMD)

  19. Results: Excitation spectra of 21LNe • Energy Spectra of 21LNe a+Ocluster Mean-field like Mean-field like a+Ocluster Kp = 0-⊗L Kp = 0- band 20Ne (AMD) 21LNe (AMD) Ground⊗L Ground band

  20. Results: Shrinkage effect • L reduces nuclear matter RMS radii • Reduction of the RMS radii is larger in the Kp = 0- (a + 16O + L) than in the ground band Kp=0-band (a + 16Ocluster) Ground band (intermediate structure) Large shrinkage mainly comes from the reduction of a + 16O distance 21LNe 20Ne 20Ne 21LNe (1/2)- 1- 0+(g.s.) (1/2)+

  21. Results: B(E2) reduction • Intra-band B(E2) values Ground band (Intermediate) Kp=0- band (Pronounced a + 16O) Larger B(E2) reduction in the Kp=0-band

  22. How does L modify exotic cluster structure ? 2. neutron-rich L hypernuclei Examples: 12LBe (Theoretical prediction) Molecular orbit structure of Be isotopes H. Homma, M. Isaka and M. Kimura

  23. Exotic structure of11Be 4 • Parity inverted ground state of the 11Be7 • The ground state of 11Be isthe 1/2+, while ordinary nuclei have a 1/2- state as the ground state Vanishing of the magic number N=8 Inversion 1/2+state 1/2+state 1/2- state 1/2- state

  24. Exotic structure of 11Be 4 • Parity inversion of the 11Be7 ground state • The ground state of 11Be is 1/2+ • Main reason of the parity inversion: molecular orbit structure • 11Be has 2a clusters with 3 surrounding neutrons 11Be 1/2- Extra neutrons in p orbit[1] inversion 11Be 1/2+ Extra neutrons in s orbit[1] Extra neutrons occupy molecular orbits around the 2a cluster [1] Y. Kanada-En’yo and H. Horiuchi, PRC 66 (2002), 024305.

  25. Excitation spectra of 11Be 11Be 1/2- 11Be(AMD) 11Be(Exp) 13C(Exp) b=0.52 11Be 1/2+ b=0.72 • Deformation of the 1/2- state is smaller than that of the 1/2+ state

  26. Excitation spectra of 11Be 11Be 1/2- 11Be(AMD) 11Be(Exp) 13C(Exp) Extra neutrons in p orbit[1] (small deformation) 11Be 1/2+ Extra neutrons in s orbit[1] (large deformation) Difference in the orbits of extra neutrons • Deformation of the 1/2- state is smaller than that of the 1/2+ state • Parity reversion of the 12LBe ground state may occur by L in s orbit [1] Y. Kanada-En’yo and H. Horiuchi, PRC 66 (2002), 024305.

  27. Structure change in 12LBe 11Be 1/2- Extra neutrons in porbit (small deformation) 11Be 1/2+ 11Be Extra neutrons in sorbit (large deformation) Parity inverted 1/2- 1/2+ What is happen by L in these states with different deformations? Deformations are reduced? Parity-inverted ground state changes?

  28. Results: Parity reversion of 12LBe • Ground state of 12LBe 3.0 2.0 11Be7 11Be7 13C7 b=0.52 (Exp.) (Exp.) (AMD) Excitation Energy (MeV) 1.0 0.0 b=0.72

  29. Results: Parity reversion of 12LBe • Ground state of 12LBe • The parity reversion of the 12LBe g.s. occurs by the L hyperon 3.0 2.0 11Be7 11Be7 13C7 (Exp.) (Exp.) (AMD) 12LBe Excitation Energy (MeV) (HyperAMD) 1.0 0.0

  30. Deformation and L binding energy • L slightly reduces deformations, but the deformation is still different • L hyperon coupled to the 1/2- state is more deeply bound than that coupled to the 1/2+ state • Due to the difference of the deformation between the1/2- and 1/2+ states 11Be 12Be L (Calc.) (Calc.) r = 2.53 fm 0.32 MeV r = 2.69 fm r = 2.67 fm 1/2- 0+ (1/2+⊗Ls) 0.25 MeV r = 2.51 fm b=0.52 BL = 10.24 MeV b=0.70 1/2+ 0- (1/2-⊗Ls) BL = 9.67 MeV b=0.72 b=0.47

  31. Summary • Summary • To study structure change by L, we applied an extended version of AMD to 21LNe and 12LBe . • Coexistence of structures in sd-shell nuclei • Shrinkage effect is larger in a + 16O + L band than the ground band • Exotic cluster structure of n-rich nuclei • The abnormal parity of 11Be ground state is reverted in 12LBe • Future works: “Structure changes” • Be hyper isotopes: L modifies 2a clustering and extra neutrons? • Coexistence structures: 13LC, 20LNe, etc. • Predictions of the production cross sections Large reduction of the B(E2) values in a + 16O + L band

  32. Backup:Lbinding energy in 21LNe • The L hyperon coupled to the intermediate state is more deeply bound than that coupled to the well developed a + 16O state • The L hyperon stays around O cluster in the a + O cluster state. Kp=0I+ band Kp=0- band 20Ne shallow binding in the a + Ostate 0+ 1- BL=15.9 MeV BL=16.9 MeV 21LNe (1/2)- (1/2)+

  33. Backup: Parity Coupling • Contribution of L hyperon in p orbit • The L(s) hyperon in the “Kp=0-⊗L(s) ” stays around the 16O cluster Kp=0-⊗L(s):about 90% it is not eigenstate of parity L(p) component should contribute to the “Kp=0-⊗L(s) ” state (Parity Coupling) (1/2)- Kp=0I+⊗L(p):about 10%

  34. Backup: L hyperon in a + 16O cluster structure • 21LNe: Kp=1-⊗Ls state Energy (MeV) (1/2)- Quadruple deformation parameter b

  35. Deformation change by L in p-orbit C 13 L • From changes of energy curves 12C (Pos) 12C(Pos)⊗L(p) 9LBe b = 0.27 b = 0.30 adding L in p orbit 20LNe quadrupole deformation b Lin p-orbit enhances the nuclear deformation 1.5 Spherical 1 Opposite trend to L in s-orbit 21LNe

  36. L binding energy • Variation of the L binding Energy • Lin s-orbit is deeply bound at smaller deformation • Lin p-orbit is deeply bound at larger deformation 13LC 13LC Energy curves Binding energy of L 12C(Pos.)⊗L(s) 12C Pos. 12C(Neg)⊗L(s) L binding energy [MeV] 12C(Pos)⊗L(p) E energy (MeV) 12C(Pos)⊗L(p) 12C(Pos)⊗L(s) + 8.0MeV • Variation of the L binding energies causes • the deformation change (reduction or enhancement)

More Related