Deformations of sd and pf shell  hypernuclei with antisymmetrized molecular dynamics Masahiro Isaka (RIKEN)

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 A major issue in hypernuclear physics “Hyperon as an impurity in nuclei”  hypernucleus Normal nucleusAs an impurity + Interaction: To understand baryon-baryon interaction Structure: To understand many-body system of nucleons and hyperon Today’s talk: deformation of  hypernuclei

Recent achievements in (hyper)nuclear physics Knowledge of  N effective interaction Study of light (s, p-shell)  hypernuclei –Accurate solution of few-body problems [1] –  N 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 [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’yo et al., PTP 93 (1995), 115. Recent developments enable us to study structure of  hypernuclei

Toward heavier and exotic  hypernuclei Experiments at JLab and J-PARC etc. Hypernuclear chart will be extended to heavier regions Taken from O. Hashimoto and H. Tamura, PPNP 57(2006),564. “Structure of hypernuclei” Coexistence of shell and cluster Exotic cluster Developed cluster p-sd shell region Light  hypernuclei n-rich region sd-pf shell region Today’s talk: Various deformations Triaxial deformation + 41  Ca, 39  Ar 25  Mg Coexistence of deformations

Deformation of nuclei Many nuclei manifests various quadrupole deformation Most of them are prolate or oblate deformed (axially symmetric) (parameterized by quadrupole deformation parameters  and  )  = 0 ◦  ≈ 30 ◦ Spherical  = 60 ◦   0 0◦0◦ 60 ◦ Long Middle Short Triaxial Oblate (axially symmetric) Prolate (axially symmetric)  = 0 Today’s talk: Various deformations Triaxial deformation + 25  Mg Coexistence of deformations 41  Ca, 39  Ar

Topic 1: Coexistence of deformations in A ≃ 40 nuclei Different deformations could appear in the excited states in a nucleus Svensson et al., PRC63, R (2001). Ideguchi, et al., PRL 87, (2001) O’Leary, et al., PRC61, (2000). Superdeformed(SD) states With 1:2 axis ratio of deformation Observed in 40 Ca, 36 Ar and 44 Ti If a  particle is added, what is happen? Various deformed states also appear in 38 Ar  ≃   ≃  1 2  ≃ 

Topic 2: Triaxial deformation of nuclei Largely deformed Low-lying 2nd 2 + indicates having the triaxial deformation Ex.) 24 Mg Our task: to identify triaxial deformation of 24 Mg by using  Triaxial deformed nuclei are not many, Mg isotopes are the candidates Identification of triaxial deformation is not easy

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

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

Theoretical Framework: HyperAMD  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 M.Isaka, et al., PRC83(2011) M. Isaka, et al., PRC83(2011)

1. Coexistence of deformations M.Isaka, M. Kimura, E. Hiyama, H. Sagawa, and Y. Yamamoto Examples: 41  Ca, 39  Ar What is the difference in responses among deformations ? 1:2 Addition of  spherical Various deformations SD

Topic 1: Coexistence of deformations in A ≃ 40 nuclei Different deformations could appear in the excited states in a nucleus Svensson et al., PRC63, R (2001). Ideguchi, et al., PRL 87, (2001) O’Leary, et al., PRC61, (2000). Superdeformed(SD) states With 1:2 axis ratio of deformation Observed in 40 Ca, 36 Ar and 44 Ti If a  particle is added, what is happen? Various deformed states also appear in 38 Ar

B  with different deformations(structures)   binging energy (B  ) in light  hypernuclei with cluster structure  coupled to the compact state is more deeply bound Changes of excitation spectra Ex.) 10  Be (  +  + n +  ) 4 body calc.: E. Hiyama and Y. Yamamoto, PTP128(2012)105 8 Be(0 + ) + n(p-orbit)    8 Be(0 + ) + n(s-orbit)   

Expected difference of B   Examples: 41  Ca ( 40 Ca  ), 39  Ar ( 38 Ar +  ) Purposes: to reveal difference of B  depending on deformations Which is the largest?

ND and SD states of 40 Ca Ground, normal deformed and superdeformed states are obtained Y. Taniguchi, et al., PRC 76, (2007) Core nucleus 40 Ca: basically same calculation as 1:2 spherical   ≃ 

Results: Energy curves of 41  Ca as a function of  40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca 41 Ca   “GS ⊗  ”, “ND ⊗  ” and “SD ⊗  ” curves are obtained SD states will appear in 41  Ca spherical superdeformed 40 Ca 41 Ca  spherical 41 Ca  superdeformed Energy (local) minima are almost unchanged

Definition: General trend:   changes within MeV as  increases Results:  single particle energy  single particle energy GS NDND SDSD 41 Ca  40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca Energy surface 

Results:  single particle energy   varies due to changes of spatial overlap between  and N –Deformation of  distribution is small, while nuclear part is deformed  GS  NDND  SDSD matter    GS NDND SDSD 41 Ca  40 Ca(Pos)⊗  (s)

Results: Difference of  binding energy B  ND and SD states are predicted in 41  Ca B  is different among ground, ND and SD states 40 Ca 41 Ca  Largest

Many kinds of deformed states in 38 Ar Several deformed rotational bands are observed They have different deformations with different nucleon configurations D. Rudolph, et al., Phys. Rev. C (2002)

Results: Energy curve and  single particle energy 39 Ar  Energy (local) minima are almost unchanged   changes within MeV as  increases 38 Ar Energy (local) minima with different deformations appear Energy curve  single particle energy  

Results: Difference of B  Excited staes with different deformations are predicted in 39  Ar B  is different depending on deformations and consistent with   

Other predictions of B  B  is larger in the SD state in 39  Ar, etc. Bing-Nan Lu, et al., Phys. Rev. C89, (2014) Localization of nucleons makes  deformed 38 Ar SD ground MeV MeV 39 Ar  Large spatial overlap between N and  Large B  Large B  in the SD state will give important information about localization Matter density of 39 Ar SD ground 

2. Triaxial deformation Based on M.I., M. Kimura, A. Dote, and A. Ohnishi, PRC87, (R) (2013) Examples: Mg To identify triaxial deformation by using  in p orbit

Deformation of nuclei Triaxial deformed nuclei are not many Its identification is not easy Prolate Oblate Triaxial  = 0 ◦  ≈ 30 ◦ Spherical  = 60 ◦   0 0◦0◦ 60 ◦ Candidate: Mg isotope Long Middle Short “  in p orbit can be a probe to study nuclear (triaxial) deformation”

Triaxial deformation If 24 Mg is triaxially deformed nuclei Large overlap leads to deep binding Middle Small overlap leads to shallow binding cf. prolate deformation Ex.) 9  Be p orbit parallel to 2  (long axis) p orbit perpendicular to 2  (short axes) Large overlap Deeply bound Split corresponding to long/short axes Small overlap Shallowly bound Triaxial deformation Prolate deformation p-states split into 3 different state

Triaxial deformation If 24 Mg is triaxially deformed nuclei Large overlap leads to deep binding Middle Small overlap leads to shallow binding Triaxial deformation Prolate deformation G.S. Excitation Energy 25  Mg 24 Mg ⊗  s-orbit) 24 Mg ⊗  p-orbit) Split into 3 states? p-states split into 3 different state Observing the 3 different p-states is strong evidence of triaxial deformation Our (first) task: To predict the level structure of the p-states in 25  Mg

Results ： Single particle energy of  hyperon   single particle energy on  plane Single particle energy of  hyperon is different from each p state –This is due to the difference of overlap between  and nucleons 25 Mg (AMD,  in p orbit)  Lowest p state2nd lowest p state3rd lowest p state

Results ： Single particle energy of  hyperon    s. p. energy is different from each other with triaxial deformation 25 Mg (AMD)  Lowest p state (Parallel to long axis) 2nd lowest p state (Parallel to middle axis) 3rd lowest p state (Parallel to short axis) I II III I II III I II III Lowest 2nd Lowest 3rd Lowest 3 p-states with different spatial distributions of  in p-orbit I II III

Results: Excitation spectra 3 bands are obtained by  hyperon in p-orbit – 24 Mg ⊗  p(lowest), 24 Mg ⊗  p(2nd lowest), 24 Mg ⊗  p(3rd lowest) Lowest threshold : in between 8.3 and 12.5 MeV Ne + 21   Splitting of the p states

Triaxial deformation of 26 Mg: 27  Mg 26 Mg (AMD) Energy surface (0 + state) 27  Mg (AMD) Similar discussions can be possible in the other Mg isotopes

Summary  Summary AMD + GCM was used to study deformations of sd-pf shell  hypernuclei  added to various deformed states: 41  Ca and 39  Ar Various deformed states in  hypernuclei –Deformation is almost unchanged by  –B  is different depending on deformations Largest in the ground state Smaller in the deformed state such as SD states  as a probe to study triaxial deformation: 25  Mg  in p-orbit generates three different p states in 25  Mg –This is due to the triaxial deformation of the core nucleus  Future plan To predict the production cross sections Comparison of B  with cluster states: 13  C (Hoyle +  )

Backup

Structure of 24 Mg Large deformation ・・・ Candidate of triaxial deformed nuclei Excitation energy of K  =2  band depends on the triaxial deformation [1,2] [1] M. Bender and P-H. Heenen, Phys. Rev. C78, (2008). [2] M. Kimura, R. Yoshida and M.Isaka, Prog. Theor. Phys. 127, 287(2011).

Structure of 24 Mg Low lying K  =2  band: a sign of triaxial deformation Excitation energy of K  =2  band depends on the triaxial deformation M. Bender, P-H. Heenen, PRC78, (2008)., M. Kimura, R. Yoshida, M.I., PTP 127, 287(2011). Ex K  = 2  band is rigid against the exclusion of the triaxial deformation Does  particle change these two bands?

Results: Excitation spectra of 25  Mg Excitation energy of K  =2  ⊗  s band is shifted up by about 200 keV 200keV

Back up: Superdeformation SD is due to the large shell gap at certain deformations Taken from E. Ideguchi, et al., PRL 87, (2011)

ND and SD states of 40 Ca Ground, normal deformed and superdeformed states are obtained Y. Taniguchi, et al., PRC 76, (2007) Core nucleus 40 Ca: basically same calculation as 1:2 spherical   ≃ 

Energy curves of 41  Ca as a function of  40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca 41 Ca   “GS ⊗  ”, “ND ⊗  ” and “SD ⊗  ” curves are obtained SD states will appear in 41  Ca spherical superdeformed 40 Ca 41 Ca  spherical 41 Ca  superdeformed Energy (local) minima are almost unchanged

Definition: General trend:   changes within MeV as  increases  single particle energy GS NDND SDSD 41 Ca  40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca Energy surface 

Definition: General trend:   changes within MeV as  increases  single particle energy GS NDND SDSD 41 Ca  40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca Energy surface  13 C  13 C(Pos)⊗  (s) Similar to the p shell  hypernuclei

Difference of  binding energy B  ND and SD states are predicted in 41  Ca B  is different among ground, ND and SD states 40 Ca 41 Ca  Largest

Superdeformed states in Sc hypernuclei Various deformations coexist in the g.s. regions We predict ND and SD states with mp-mh configuration Examples: 46  Sc, 48  Sc Core nuclei ( 45 Sc, 47 Sc) Difference of B   depending on deformation by adding a 

Excitation spectra of 46  Sc and 48  Sc Difference of B  leads to the energy shift up of the deformed states Similar phenomena in 48  Sc We hope these states in Sc  hypernuclei  are observed at JLab Shifted up

Changes of the excitation spectrum in 48  Sc We predict mp-mh states with various deformations in 47 Sc Difference of B  and shift up of the deformed states in 48  Sc Shifted up

Energy surface as a function of  Ground, normal deformed and superdeformed states are obtained 45 Sc(Neg)⊗  (s) 45 Sc(Pos)⊗  (s) 45 Sc(Pos) 45 Sc(Neg) GS ND SD 45 Sc 40 Ca(Pos)⊗  (s) 40 Ca(Pos) GS ND SD 40 Ca Energy (local) minima are almost unchanged

Backup: Structure of the core nuclei Examples: 40 Ca, 45 Sc, 47 Sc and corresponding  hypernuclei

ND and SD states of 40 Ca Ground, normal deformed and superdeformed states are obtained Y. Taniguchi, et al., PRC 76, (2007) pf sd ND pf sd SDSD pf sd protonneutron GS Configuration Core nucleus 40 Ca: basically same calculation as

Configurations of nucleons Number of the deformed harmonic oscillator quanta pf sd ND pf sd SDSD pf sd protonneutron GS 40 Ca (+) GS

Configurations of nucleons

45 Sc: Configurations of nucleons protonneutron pf sd GS

45 Sc: Configurations of nucleons protons: similar to SD states of 40 Ca SD pf sd protonneutron protonneutron pf sd GS

47 Sc: Configurations of nucleons GS protonneutron pf sd ND2 pf sd protonneutron protons: similar to SD states of 40 Ca neutrons: similar to the GS

Excitation spectrum of 45 Sc Various deformed states are predicted in 45 Sc including SD states We hope SD band is observed by forthcoming experiment at RCNP 45 Sc (Expt.) 45 Sc (AMD)

Excitation spectrum of 47 Sc

Short summary AMD + GCM framework has been applied to 45 Sc and 47 Sc to investigate deformed excited states. Various deformed states with many-particle many-hole configurations –In 45 Sc, prediction of the SD states with proton 4p configuration –In 47 Sc, deformed states with 4p proton configuration, but neutron configuration is the same as the GS. Increase of neutron number may affect neutron configuration? Further investigations are required 47 Sc protonneutron SD in 45 Sc protonneutron SD in 40 Ca protonneutron

Backup: Configurations of nucleons protonneutron Ground pf sd ND2 pf sd ND2 pf sd ND1 SD pf sd pf sd N p = 33 N n = 42 N p = 35 N n = 42 N p = 35 N n = 44 N p = 34 N n = 42 N p = 36 N n = 44

Backup: Configurations of nucleons protonneutron ND2 ND1 ND2 pf sd ND1 pf sd Ground pf sd pf sd pf sd N p = 33 N n = 48 N p = 35 N n = 48 N p = 35 N n = 50 N p = 34 N n = 48 N p = 36 N n = 48

Results: Energy curve 38 Ar Energy (local) minima with different deformations appear

Results: Energy curve 39 Ar  “GS ⊗  ”, “ND ⊗  ” and “SD ⊗  ” curves are obtained Energy (local) minima are almost unchanged 38 Ar Energy (local) minima with different deformations appear

Definition: General trend:   changes within MeV as  increases Results:  single particle energy  single particle energy Energy surface 38 Ar(Pos)⊗  (s) 38 Ar(Pos) 

Results:  single particle energy   varies due to changes of spatial overlap between  and N –Deformation of  distribution is small, while nuclear part is deformed    

Results: Difference of B  Excited staes with different deformations are predicted in 39  Ar B  is different depending on deformations and consistent with   

Other predictions of B  B  is larger in the SD state in 37  Ar, etc. Bing-Nan Lu, Emiko Hiyama, Hiroyuki Sagawa and Shan-Gui Zhou, arXiv: v1 Localization of nucleons makes  deformed Distributions of  SD ground Matter density of 37 Ar SD ground  36 Ar SD ground MeV MeV 37 Ar  Large spatial overlap between N and  Large B  Large B  in the SD state will give important information about localization