CNS, University of Tokyo S. Shimoura Chiba

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1 CNS, University of Tokyo S. Shimoura

Isospin symmetry New Magic Numbers Shape Coexistence Neutron Skin/Halo Di-neutron correlation

2 Introduction Structure and Dynamics of Nuclei as functions of N and Z in a wide area of nuclear chart Collectivities / Single-Particle Properties of Nuclear Matter Decoupling of P and N <=> Isospin symmetry New Magic Numbers Shape Coexistence Neutron Skin/Halo Di-neutron correlation Giant/Pigmy Resonances Known ~ Available now > 10 3 /s /s /s Theoretical Prediction

3 Size/ρ-distribution Skin/Halo Shell Structure New magic # Isospin / Deformation New modes etc. IVE1 ISE0, ISE1 " L, " S, " J " T; q,!,... Size/ρ-distribution σ R, elastic scat. Shell Structure Mass / S n, S 2n Inelastic scatt. Low lying states Knockout / Transfer New modes Coulex Inelastic scatt. CEX etc.

4 Introduction Structure information of nuclei as functions of N and Z Shell Evolution Collectivities (clustering) / Single particle structure in excited states Nuclear responses 14 O 22 O Disappearance of N=20 magicity 12 Be Disappearance of N=8 magicity Deformation / Cluster structure

5 Inverse Kinematics w/ RI beam RI beam ( pps; ΔE~a few %) Exc. States γ rays Decay Fragments Target as probe Interaction Formation of Excited States of Exotic Nuclei Direct reactions and their selectivities In-beam spectroscopy measuring decay products Invariant-mass/γ-ray spectroscopy Particle detectors at forward angles (kin. focus.) Gamma detectors surrounding target (Doppler shift) Missing-mass spectroscopy Recoil & Active Target Measurement Dispersion Matching/Measurement

6 Probes for direct reactions Heavy Nuclei: Strong Coulomb Field Coulomb Excitation, Coulomb Dissociation E1, E2, (M1) / Isovector H, D, 4 He [Liquid targets] Inelastic Scattering Isovector (H) / Isoscaler(H, D, 4 He) Spin-Flip (H, D) / Spin-Non-Flip (H, D, 4 He) Charge Exchange Fermi type (H) / Gamow-Teller type (H, D) Nucleon Transfer (α,t), (α, 3 He) Reaction Knockout Other (Be, C, ) Inelastic Scattering Knockout / Fragmentation Dirty RI beams and/or Changing Target Same Nucleus can be populated via Different Processes without changing Detector System

Liquid Helium Target (CRYPTA) 100-250 mg/cm 2 24-30 mm φ 7µm Havar window Kept less than 4K sealed with Al cylinder

7 Liquid Helium Target (CRYPTA) mg/cm mm φ 7µm Havar window Kept less than 4K sealed with Al cylinder Melting point of helium is 1atm Developed by CNS/Rikkyo/RIKEN Cold head H. Ryuto et al., NIMA 555 (2005) 1 Target

8 Observables reaction/decay meas. Yields (Cross Sections) / Lifetime / Width Spectra : As a function of Exc. Energy (+ incident energy) Properties of populated states ( Selectivity) Angular Distribution / Momentum Transfer Assignment of L J π Eikonal Model [Knockout] Virtual Photon / DWBA / Coupled Channels [Coulex, Inelastic, Transfer] Optical Potential / Transition Density Folding Model with Density Dependent Effective Interaction Angular Correlation / Alignments Assignment of J π Cross sections as a function of

9 Typical Setup of Experiment inverse kinematics 30% Doppler Gamma-ray detector 75 Charged particle detector Plastic scintillator ΔE, E, and position 12 Be vacuum 12 Be, 13 B F3 Beam tracker Position and direction Separate high and low vacuum 120mg/cm 2 4K β 0.3 H. Ryuto et al., NIMA 555 (2005) 1

10 Analysis of Alpha inelastic excitation WF s of gnd. and exc. states (φ 0 (r), φ(r)) Gnd. State density (ρ 0 (r)) Distorting pot. (V 0 (r)) O.M. analysis Elastic Scat. Data Global Systematics Microscopic Macroscopic BM; Tassie α, β, δ Folding with effective interaction v eff Macroscopic BM β, δ DWBA transition density (ρ tr (r)) Transition pot. (V tr (r)) Experimental Data Integrated C.S., Ang. Distr. Ang. Cor. J π, δ=βr, Transition Matrix Element δ sum rule

11 Alpha inelastic scattering DWBA by using single folding model with DD interaction Collective form factor Compression mode Tassie model

12 γ γ spectrum coincident with 12 Be ejectiles 2.1 & 2.7 MeV States excited by (α, α ) DWBA [ col. FF & folding pot.] Angular Distributions of 12 Be*

14 γ γ α α 2.1 & 2.7 MeV States excited by (α, α ) Alignments of 12 Be* Anisotropic Angular Distribution of γ Consistent with Prediction of DWBA calculation assuming 2 + & 1 - excitation, resp. Confirmation of 1 - assignment for 2.7 MeV state

15 Alpha inelastic scatterings 4 He( 14 O, A MeV No bound states in 14 O 14 O* 13 N+p, 12 C+2p, 12 C*+2p, 10 C+α, 10 C*+α Isoscalar E0 & E1 modes (compression) Multipole Decomposition Analysis (MDA) of Isoscalar excitation Effect of Continuum

16 Compression modes Isoscalar Vibration Compression modes

17 14 O 14 C (mirror pair; sub magic) No bound state O 14 C 6 bound states 1, 0 +, 3, 0, 2 +, 2

18 4 He( 14 O, 14 O * ) at 60 A MeV 14 O* 13 N+p, 12 C+2p, 12 C*+2p, 10 C+α, 10 C*+α

19 4 He( 14 O, 14 O * ) at 60 A MeV G.S. Density of 14 O L=0 L=1 L=2 L=3 Relativistic mean field (TIMORA) HO density Angular distributions for two (Unfold from e-scat. on 14 C) types of 14 O density

20 4 He( 14 O, 14 O * ) at 60 A MeV (MDA) Angular distributions 1 - state at Ex=5.17 MeV Ex= MeV Ex=15 16 MeV

21 Partial Cross Sections for each Multipole 4 He( 14 O, 14 O * ) - MDA L=0 L=1 L=2 L=3 L>3 13 N+p Ex (MeV) Ex (MeV) Chiba All L=0 L=1 L=2 L=3 L>3 40% 78% 16% 10% Fraction of EWSR (Ex<25 MeV)

22 4 He( 14 O, 14 O * ) : Strength distribution Dipole L=0 L=1 RPA Calc. (Sagawa) RPA Calc. (Sagawa) 14 C 14 O 5 Ex (MeV) 20 5 Ex (MeV) 20 One bound 0 + state in 14 C One bound 1 - state in 14 C

23 Alpha inelastic scattering to highly excited cluster states 4 He( 12 Be, 6 He+ 6 He) & 4 He( 12 Be, 4 He A MeV Cluster states in 12 Be L=0, 2, (4) excitations Multipole Decomposition Analysis (MDA) including decaying process

24 E x spectra of 6 He+ 6 He & α+ 8 He 6 He+ 6 He α+ 8 He

25 Angular distribution of (α,α ) Angular correlation of 6 He+ 6 HeDecay (interference) d d & 2 MDA analysis = " ineld" decay l, m 2 * (# ) Y ( )!% l$ lm lm " decay

26 100% Same method (with odd l) is applied for 4 He+ 8 He channel (preliminary)

27 6 He+ 6 He α+ 8 He Very preliminary

28 6 He 6 He α α kev Freer et al. Bohlen et al. 210 kev 360 kev α n n α + n n α 8 He α α + + -

29 M. Ito, N. Itagaki, H. Sakurai, and K. Ikeda, Phys. Rev. Lett. 100, (2008)

30 4 He( 12 Be, 6 He 6 He), 4 He( 12 Be, 4 He 8 He) MDA. Resonant states including negative parity states Lifetime of 12m Be(0 + ) Large mixing of (p) 2 and (sd) 2 $ "! + #! ~ (π) 2 ~ (σ) 2 #! + "!

31 Nucleon Transfer from A MeV Proton Single particle states in neutron-rich nuclei 4 He( 12 Be, 13 Bγ) [S. Ota et al., Phys. Lett. B 666 (2008) 311] 4 He( 22 O, 23 Fγ), [ 4 He( 23 F, 23 Fγ), 4 He( 24 F, 23 Fγ), He( 25 Ne, 23 Fγ)] utilizing cocktail beams [S. Michimasa et al., Phys. Lett. B 638 (2006) 146] p n

32 Nucleon (Proton) Transfer from Alpha (d,n), ( 3 He,d), (α,t), Incident energy higher than 30 MeV/u Thicker target (100~200 mg/cm 2 ) Less distortion effect Less multi-step process Same optical potential as inelastic excitation Identification by comparing with other direct reactions But x Momentum mismatch

33 Momentum Matching Condition (Classical) As if Getting off from the moving train (projectile) to platform (target) Internal motion in the train (Fermi motion in the projectile) along the opposite direction of the train (target) Motion on the platform (Fermi motion of the nucleon on the target) along the direction of the train

34 Momentum Matching Condition (QM) % % r k c' c' xb T T " [ c] [ c'] a + A! b + B Post PW Prior PW V V = 2 a xb xa b a % % = = c c r k c =! a B!! = ( b + = ( A + c' r & k c' = & = & c' V V xb xa x) + V ( 2$ ) ( 2$ ) r ; k " 2 B xa x) Plane Wave Born Approx. h 2 ; h V 3 =! ba ba 2 h 2µ c! c! xb 2 h 3 2µ xa r = k & c a B 2µ xb 2µ Binding energies of a and B xa a x r xb b r c r c r xa B r r r ikxb ( xb 3 r ( k + " ) d r # ( ) e d r # *( ) xb r r r ikxb ( xb 3 r ( k + " ) d r # ( ) e d r # *( ) A B xa r k c' a B ' ' xb xb a a xb xb ' ' xa xa B B xa xa A e e r & ik xa r & ik Fourier Components of wave functions of nucleon (x) in a and B Same value but different expressions xa r ( xa r ( xa

35 Proton Transfer in Momentum Space A MeV A MeV q (fm -1 ) Be E x =0 13 B*(10MeV) -1 p q z (fm -1 ) 0 d E x =40 n 1 q (fm -1 ) Be E x =0 E x =40 p 13 B*(10MeV) α -1 0 q z (fm -1 ) t 1 13 B* d 13 B* α

36 DWBA Calculation Example: 22 O(α,t) 23 F 22 O(d,n) 23 F

37 N-rich N=8 Nuclei Spin-orbit splitting between νp 1/2 & νp 3/2 depend on the number of protons in πp 3/2 orbit attracting νp 1/2 orbit V Τ p n n-rich Boron 8 sd p 1/2 p 3/2 6 p n n-rich Beryllium sd p 1/2 p 3/2 12 Be Low-lying 2 + state Low-lying 1 - state Low-lying state Magicity loss in N=8 Deformed ground state Change of Boron Proton Shell as a function of configuration sd p 1/2 sd p 1/2 13 B Spherical ground state How about excited states? p n p n 13 B 13 gs B* Deformed core + proton? Chiba p 3/2 p 3/2

38 4 He( 12 Be, A MeV Deformed 12 Be core + 1 proton? C 2 S(BM) ~ 0.27 for δ=0.4 β( 12 Be(p,p )) ~ [101]1/2 Spherical G.S. Deformed Excited 1/2 +? [220]1/2 [101]3/2 ε 2 ~ δ ~ 0.95β 0.3 [110]1/2

39 Spectra of 14 C, 12 Be, 11 B, and 13 B S n = C 11 B 13 B Be

40 4 He( 12 Be, A MeV CNS GRAPE NaI(Tl) array 12 Be beam 4.83 MeV states strongly excited by (α, t) Liq. He target

41 4 He( 12 Be, A MeV Angular Distribution of 13 B coin. with 4829 kev γ FR-DWBA (DWUCK5) Optical Potential: 12 C + 4 He (entrance) 12 C + 3 He (exit) L=0 -> J π = 1/2 + C 2 S ~ 0.2 -> Proton single particle state on 12 Be

42 4 He( 12 Be, A MeV Proton single particle state on 12 1/2+ Be: /2+ : 0.003?? 1/2+ : 0.03? 1/2- : /2- : /2+ 5/2+ 1/2+ : 0.01 PSDFU PSDFU Chiba 3/2- Shell model (3hw)

13 B(1/2 + 1) Present calc. Hyper deformation? 1/ E x + 2 1! 8 MeV! = 0.73 2 3 h# = ( sd) " ( sd)!

43 13 B(1/2 + 1) Present calc. Hyper deformation? 1/ E x + 2 1! 8 MeV! = h# = ( sd) " ( sd)! Proton intruder state in neutron-rich nuclei neutron proton 4He(12Be,13Bγ) Experiments By Ota et al. 1/ 2 + E x! 5 MeV + α - α By Seminar Chiba

44 1/2 + state in 13 B* by AMD Kanada-Enyo prelim.

45 Exotic Magic Number at N=16 (Z~8) Spin-orbit splitting between νd 3/2 & νd 5/2 depend on the number of protons in d 5/2 orbit attracting νd 3/2 orbit by V στ 16 d 3/2 s 1/2 d 5/2 V Τ 20 p n p n n-rich n-rich Oxygen Fluorine Excitation energy of 3/2 + S.P. state in 17 F & 23 F? d 3/2 s 1/2 d 5/2 Change of Fluorine Proton Shell as a function of Neutron number d 3/2 s 1/2 d 5/2 V Τ p n p n 17 F* 23 F*?

46 23 F spectra S. Michimasa et al., Phys. Lett. B 638 (2006) 146 Data are taken simultaneously +1p Inel. -1n -1n1p

47 S. Michimasa et al., Phys. Lett. B 638 (2006) O(a,t) 23 F*

48 νd 5/2 empty νd 5/2 full S. Michimasa et al., Phys. Lett. Seminar B 638 Chiba 146

49 SHARAQ RIBF Exp. Studies of Nuclear Many-body System Varieties in Detectors Sensitivities Nucleus Sensors Observables Materials Nuclides Probes Interactions Varieties in Nuclei N-/P-rich Nuclei RIBF Varieties in Probes Reactions using various quantum numbers Isospin (T) Spin (J, L, S) Parity (π) Energy & Momentum (ω, q) A (N, Z)... Probe

50 Motivation Response of Nuclear System using Intermediate-Energy direct reactions Studies using New Quantum Probe RI beam Large Isospin and Mass Excess Various I π ( Excited states ) Controlling Transferred Momenta, Q-values, Spin, Isospin ΔS ΔT q-ω Accessing kinematical area/conditions inaccessible by stable nuclear beam Ordinary kinematics (Missing mass spectroscopy) -> High Resolution Spectrometer + High Quality RI Beam + (Detectors of decaying particles) Asymmetric nuclear System studied using stable probes Inverse kinematics + Invariant Mass / γ-decay / Recoil and High-resolution missing-mass spectroscopy

51 Int. E Direct reactions ( A MeV) Weak Distortion :Minimal central force Effective Interaction : Spin-Isospin modes d' d$ ~ % fi (& )# C t ( q) " % ( q) r ST ~ v r 3 iq" 2 tr ( q) d r % ( r) e dr r R ( r) j ( qr) Y ( qˆ ) =! fi =! r fi 2 l l k f θ lm q k i

SHARAQ Spectroscopy with Highresolution Analyzer of RadioActive Quantum beams RI Beam (E = 150 400 MeV/A) as a new PROBE beam (stable) to nuclear systems Large Isospin iso-tensor excitations Large

52 SHARAQ Spectroscopy with Highresolution Analyzer of RadioActive Quantum beams RI Beam (E = MeV/A) as a new PROBE beam (stable) to nuclear systems Large Isospin iso-tensor excitations Large internal energy (q,ω) inaccessible by stable beams beam (unstable) (q,ω) ejectile (unstable) large negative Q-value Endothermic (q,ω) ejectile (stable) small Q-value Photon line: q=ω Stable Beam ω IVSMR Multi n s DGT Exothermic Charge Exchange Reactions GT SHARAQ q

53 Multi-neutron system 3,4 n ; 6,7 H with small q Resonant states? Correlation in multi-body scattering states? Correlation Spectral shape B C He LiBe H n Multi- Neutron Superheavy Hydrogen! (MeV) q (MeV/c ) Chiba 8 He 4 He 4n 4 He( 8 He, A MeV 8 Be 4 He( 18 O, A MeV

54 Multi-neutron system 2 n 3,4 He( 8 He, 8 Be) 3,4 n p s p 6,7 Li( 8 He, 8 Be) 6,7 H 4 n Double Dipole α n 2 n 2 n p s p p Dipole x Fermi/GT s n p n 7 Li 7 H

56 New Spin-Isospin Modes in nuclei: IVSMR IsoVector Spin-Monopole Resonance (IVSMR) β & β + directions ( 12 N (1 + ), 12 C), ( 12 B (1 + ), 12 C) Q=+17 MeV/ +13 MeV ( 11 Li, 11 Be*[1/2 - ]) : Q=+20 MeV Compression mode with στ O ~ r 2 στ Ex, width Spin compressibility of nuclear matter GT higher Ex 12 N 12 C (q,ω) small Q-value MeV/c qchiba ω Single Charge Exchange Reaction IVSMR GTR 50 MeV Sakai-G Project Grant-in-Aid of MEXT ( 12 N, 12 C), ( 12 B, A MeV (p,n), 800 MeV

57 New Spin-Isospin Modes in nuclei: DGTS Double Gamow-Teller States (DGTS) Not yet discovered Two-phonon response E DGTS = 2E GTS? Γ DGTS = 2 1/2 Γ GTS? Nuclear matrix elements for double beta decay ( 20 Mg, 20 Ne) ( 9 C(3/2 ), 9 Be(3/2 )) ω Double Charge Exchange Reaction DGTS 30 MeV Double β decay 30 MeV/c Sakai-G Project Grant-in-Aid of MEXT ( 20 Mg, A MeV ( 12 C, A MeV q

58 Specification dispersion (D) 5.86 m horizontal magnification (M x ) 0.40 D/M x 14.7 m momentum resolution (image size 1mm) 1/14700 vertical magnification (M y ) 0.0 angular resolution < 1 mrad vertical acceptance ± 3 deg for spot size 60mm 10mm (in dispersion matching operation) horizontal acceptance ± 1deg solid angle 2.7 msr for spot size of 10mm 10mm solid angle 4.8 msr

SHARAQ プロジェクト核反応前後でやりとりされるエネルギー運動量を高分解能で測定新しい魔法数様々な変形振動状態中性子物質高温原子核の反応 SHARAQスペクトロメータの仕様運動量分解能 Δp/p < 1/15000 高機能 RI ビームラインどれだけ音程が区別できるか分散測定

59 SHARAQ プロジェクト核反応前後でやりとりされるエネルギー運動量を高分解能で測定新しい魔法数様々な変形振動状態中性子物質高温原子核の反応 SHARAQスペクトロメータの仕様運動量分解能 Δp/p < 1/15000 高機能 RI ビームラインどれだけ音程が区別できるか分散測定最大磁気剛性 Bρ = 6.8Tm (ρ=4.8m) 始めの音の音程を測るどれだけ高い音まで測れるか分散整合立体角 ΔΩ =5 msr 始めと終わりの音程差を測るどれだけ小さな音まで測れるか運動量範囲 +/- 3% 2009年稼働開始どれだけ音域が広いか Chiba

60 Summary Alpha induced direct Reactions combined with invariant-mass/γ spectroscopy are powerful tools to investigate excited states in exotic nuclei Cluster states Isoscaler responses Nucleon transfer reactions at A MeV are useful for searching single-particle states Single particle structure Structure change in excited state Future : SHARAQ spectrometer and gamma-detector GRAPE will be used for studies at heavier exotic nuclei

Nuclear spectroscopy using direct reactions of RI beams

Nuclear spectroscopy using direct reactions of RI beams Introduction Spectroscopy of exotic nuclei (inv. kin.) Recent experimental results SHARAQ project in RIBF highly excited exotic states spectroscopy