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Dipole response of exotic nuclei and the EOS Konstanze Boretzky, GSI for the LAND-R 3 B Collaboration low-lying dipole strength nuclear matter properties predictions for relation to symmetry energy parameters dipole strength in


  1. Dipole response of exotic nuclei and the EOS Konstanze Boretzky, GSI for the LAND-R 3 B Collaboration • low-lying dipole strength �� nuclear matter properties � predictions for relation to symmetry energy parameters • dipole strength in Tin isotopes: � Coulomb excitation in inverse kinematics using LAND-R 3 B � 129-132 Sn � interpretation in terms of symmetry energy for 130 , 132 Sn, 208 Pb • experimental outlook: � decay studies: 68 Ni � dipole strength evolution in proton-rich nuclei � new systematic investigations EQUATION OF STATE Konstanze Boretzky – Emmi workshop July 2010

  2. Dipole response of exotic nuclei and the EOS symmetry energy ( ρ ) 'core' skin EQUATION OF STATE Konstanze Boretzky – Emmi workshop July 2010

  3. Dipole response of exotic nuclei and the EOS symmetry energy ( ρ ) 'core' skin EQUATION OF STATE Konstanze Boretzky – Emmi workshop July 2010

  4. symmetry energy of nuclear matter Taylor expansion per nucleon in nuclear matter : − N Z ρ α = ρ + ρ α 2 + α 4 α = E ( , ) E ( , 0 ) S ( ) Ο ( ) , 2 A K ρ = − + ρ − ρ + 2 E ( , 0 ) a 0 ( ) ... V 0 ρ 2 18 0 ∂ 2 ρ α 1 E ( , ) | ρ = = S ( ) 2 ∂ α 2 2 α = 0 p 0 ∆ p K a 4 = + ρ − ρ + ρ − ρ 2 + a 0 ( ) 0 ( ) ... 4 0 0 ρ ρ 2 2 18 0 0 J = a 4 : Symmetry energy per nucleon in pure neutron matter L ~ p 0 : symmetry energy pressure ∆ K 0 : correction to incompressibility Konstanze Boretzky – Emmi workshop July 2010

  5. symmetry energy S 2 ( ρ ) and neutron skin in 208 Pb B. A. Brown PRL 85 (2000) 5296 & S. Typel & B.A. Brown PRC 64 (2001) 027302 • strong linear correlation between neutron skin and a 4 , p 0 • no distinct correlation to other quantities R.J.Furnstahl NPA 706(2002)85-110 Konstanze Boretzky – Emmi workshop July 2010

  6. pygmy dipole resonance and neutron skin "... ,the pygmy dipole resonance may place important constraints on the neutron skin of heavy nuclei and, as a result, on the equation of state of neutron-rich matter." J. Piekarewicz, PRC 73 (2006) 044325 RRPA (DD-ME2, 132 Sn Σ B PDR (E1)/ Σ B GDR (E1) [%] a 4 =30-38 MeV) neutron skin thickness [fm] RQRPA N.Paar Konstanze Boretzky – Emmi workshop July 2010

  7. Experimental Approach: Electromagnetic excitation at high energies 129-132 Sn, 133,134 Sb 58 Ni, 67-69 Ni b>R P +R T Absorption of Pb ‘virtual Photons’ σ elm ~ Z 2 1 st order pertubation theory: High velocities β ≈ 0.6-0.9 ⇒ High-frequency Fourier components d σ elm / dE = N γ (E) σ γ (E) E γ , max ≈ 18 MeV (for β = 0.8) Konstanze Boretzky – Emmi workshop July 2010

  8. Exp. Approach: Production of fission-fragment beams � Primary: 3*10 8 238 U/spill @550MeV/u � Secondary (mixed): 50 ions 132 Sn/spill (~10/sec @500 MeV/u) ρ A B e = βγ Z m c u B ρ – from position at middle focal plane of the FRS 132 Sn β – from TOF Z – from ∆ E LAND Konstanze Boretzky – Emmi workshop July 2010

  9. Experimental Approach: The LAND reaction setup @ GSI Konstanze Boretzky – Emmi workshop July 2010

  10. Results: even neutron rich Sn isotopes photoneutron cross section σ ( γ ,Xn) [ mb ] 400 124 Sn stabile nucleus 300 (real photons) 200 theoretical Coulomb experimental Coulomb cross section radioactive nucleus cross section 100 (virtual photons) d σ /dE * [ mb/MeV ] σ ( γ ,Xn) [ mb ] 400 300 300 (1n) (2n) (3n) 130 Sn 300 200 200 PDR 200 • position: ~ 10 MeV 100 100 • strength: 100 some % TRK d σ /dE * [ mb/MeV ] σ ( γ ,Xn) [ mb ] Sumrule 400 300 300 (1n) (2n) (3n) 132 Sn • accordance with 300 predictions 200 200 200 GDR 100 100 100 • no deviation from systematics 10 20 10 20 10 20 E * [ MeV ] E * [ MeV ] E * [ MeV ] P. Adrich et al., PRL 95 (2005)132501 Konstanze Boretzky – Emmi workshop July 2010

  11. Low-lying strength in 132 Sn mass region observed in all isotopes difference between even and odd isotopes due to neutron separation threshold location and unpaired neutrons Konstanze Boretzky – Emmi workshop July 2010

  12. Low-lying strength in 132 Sn mass region Konstanze Boretzky – Emmi workshop July 2010

  13. Low-lying strength in 132 Sn mass region real photon measurements at S-Dalinac: N= 82: PLB 542 (2002) 43 208Pb: PRL 89 (2002) 272502 40-48Ca: PRL 93 (2004) 192501 116,124Sn: PRC 57 (1998) 2229 Konstanze Boretzky – Emmi workshop July 2010

  14. Asymmetry parameters and neutron skins from experimental dipole response Σ B PDR (E1)/ Σ B GDR (E1) [ % ] Σ B PDR (E1)/ Σ B GDR (E1) [%] RQRPA calculations 12 130 Sn 132 Sn from 10 < p 0 > = 2.3 ± 0.8 MeV/ fm 3 8 N. Paar 6 < a 4 > = 32.0 ± 1.8 MeV 4 2 0.35 130 Sn 132 Sn R n -R p [ fm ] 0.3 R n -R p [fm] 0.25 R n -R p = 0.23 ± 0.04 fm R n -R p = 0.24 ± 0.04 fm 0.2 0.15 1 2 3 4 5 6 1 2 3 4 5 6 p 0 [MeV/fm 3 ] p 0 [MeV/fm 3 ] p o [ MeV/fm 3 ] p o [ MeV/fm 3 ] A. Klimkiewicz, N. Paar et al., PHYSICAL REVIEW C 76 , 051603(R) (2007) Konstanze Boretzky – Emmi workshop July 2010

  15. neutron skin thickness in Sn isotopes neutron skin thickness [fm] mass number of Sn isotopes stable isotopes: iv. GDR method A.Krasznahorkay et al., NPA 567 (1994) 521-540 radioactive isotopes: PDR/GDR method A. Klimkiewicz et al., PRC 76 (2007) 051603(R) Konstanze Boretzky – Emmi workshop July 2010

  16. 208 Pb analysis RQRPA- N.Paar ∑ B pdr (E1)=1.98 e 2 fm 2 from N.Ryezayeva et al., PRL 89(2002)272501 ∑ B gdr (E1)=60.8 e 2 fm 2 from A.Veyssiere et al.,NPA 159(1970)561 a 4 = 31.4 ± 0.8 MeV RQRPA- p 0 = 2.1 ± 0.3 MeV / fm 3 N.Paar δ r = 0.17 ± 0.02 fm A.Krasznahorkay et al. NPA 567(1994)521 C.J.Batty et al. Adv.Nucl.Phys. (1989)1 RQRPA- M.Csatlos et al. NPA 719(2003)C304 N.Paar B.C. Clark et al. PRC 67(2003)044306 our approach Konstanze Boretzky – Emmi workshop July 2010

  17. new contributions/contradictions Konstanze Boretzky – Emmi workshop July 2010

  18. new contributions/contradictions Konstanze Boretzky – Emmi workshop July 2010

  19. open questions • theory: � connection between PDR and symmetry energy parameters? • experiment: � systematics of dipole strength function? (mass, binding energies, asymmetry…) � new more systematic measurements � collectivity? � decay modes (direct gamma and particle decay modes) � role of the particle threshold? � sensitivity above and below threshold for exotic nuclei � connection to measurements for stable nuclei � structure of low-lying strength? � use of different probes, i.e. isoscalar probes � PDR strength in proton-rich nuclei? � adressed in 32 Ar experiment – under analysis Konstanze Boretzky – Emmi workshop July 2010

  20. Isovector and isoscalar electric dipole and quadrupole response of neutron-rich Sn nuclei accepted proposal at GSI What is new? • adress 124 Sn to 134 Sn • higher intensities • higher resolution, better mass reconstruction, less complex detector response system • measurement above and below the neutron threshold • determination of E2 components • excitation via an isoscalar probe using CD 2 target Konstanze Boretzky – Emmi workshop July 2010

  21. Coulombexcitation of 132 Sn on Pb target at 300 and 600 AMeV 2*10 5 events 600 AMeV E1 simulated E2 extracted E1 300 AMeV E2 strength E2 Konstanze Boretzky – Emmi workshop July 2010

  22. proton pygmy predictions N.Paar et al., ≈ 6 % EWSR Phys.Rev.Lett. 94 (2005) 182501 Konstanze Boretzky – Emmi workshop July 2010

  23. Dipole response studies in 32 Ar and 34 Ar statistics expected: ~500 events in PDR region, ~1000 in GDR region 32 Ar 34 Ar ~150 events in PDR region, ~1500 in GDR region Konstanze Boretzky – Emmi workshop July 2010

  24. The LAND-FRS Collaboration 127-132 Sn (Exp. S221) – 57-72 Ni (Exp. S287) Konstanze Boretzky – Emmi workshop July 2010

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