Dipole response of exotic nuclei and the EOS Konstanze Boretzky, GSI - - PowerPoint PPT Presentation

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Dipole response of exotic nuclei and the EOS Konstanze Boretzky, GSI - - PowerPoint PPT Presentation

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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

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Konstanze Boretzky – Emmi workshop July 2010

EQUATION OF STATE

Konstanze Boretzky, GSI for the LAND-R3B Collaboration

Dipole response of exotic nuclei and the EOS

  • 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-R3B 129-132Sn interpretation in terms of symmetry energy for 130, 132Sn, 208Pb

  • experimental outlook:

decay studies: 68Ni dipole strength evolution in proton-rich nuclei new systematic investigations

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Konstanze Boretzky – Emmi workshop July 2010

Dipole response of exotic nuclei and the EOS EQUATION OF STATE symmetry energy (ρ)

'core' skin

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Konstanze Boretzky – Emmi workshop July 2010

Dipole response of exotic nuclei and the EOS EQUATION OF STATE symmetry energy (ρ)

'core' skin

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Konstanze Boretzky – Emmi workshop July 2010

symmetry energy of nuclear matter

A Z N Ο S E E − = + + = α α α ρ ρ α ρ , ) ( ) ( ) , ( ) , (

4 2 2

... ) ( 18 ) ( ) , ( 2 1 ) (

2 2 2 4 2 2 2

|

+ − ∆ + − + = = ∂ ∂ =

=

ρ ρ ρ ρ ρ ρ α α ρ ρ

α

K p a E S

... ) ( 18 ) , (

2 2

+ − + − = ρ ρ ρ ρ K a E

V

Taylor expansion per nucleon in nuclear matter :

J = a4:

Symmetry energy per nucleon in pure neutron matter

L ~ p0:

symmetry energy pressure

∆K0:

correction to incompressibility

a4 p0

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Konstanze Boretzky – Emmi workshop July 2010

symmetry energy S2(ρ) and neutron skin in 208Pb

  • B. A. Brown PRL 85 (2000) 5296 & S. Typel & B.A. Brown PRC 64 (2001) 027302
  • strong linear correlation between neutron skin and a4, p0
  • no distinct correlation to other quantities

R.J.Furnstahl NPA 706(2002)85-110

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Konstanze Boretzky – Emmi workshop July 2010

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

RQRPA N.Paar RRPA (DD-ME2, a4=30-38 MeV)

132Sn

ΣBPDR(E1)/ΣBGDR(E1) [%] neutron skin thickness [fm]

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Konstanze Boretzky – Emmi workshop July 2010

Experimental Approach: Electromagnetic excitation at high energies

b>RP+RT Pb

Absorption of ‘virtual Photons’

σelm ~ Z2

58Ni, 67-69Ni 129-132Sn, 133,134Sb

High velocities β ≈ 0.6-0.9

⇒ High-frequency Fourier components Eγ,max ≈ 18 MeV (for β=0.8)

1st order pertubation theory:

dσelm / dE = Nγ(E) σγ(E)

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Konstanze Boretzky – Emmi workshop July 2010

  • Exp. Approach: Production of fission-fragment

beams βγ ρ B Z A c m e

u

=

Bρ – from position at

middle focal plane

  • f the FRS

β – from TOF Z – from ∆E

LAND

Primary: 3*108 238U/spill @550MeV/u Secondary (mixed): 50 ions 132Sn/spill (~10/sec @500 MeV/u)

132Sn

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Konstanze Boretzky – Emmi workshop July 2010

Experimental Approach: The LAND reaction setup @ GSI

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Konstanze Boretzky – Emmi workshop July 2010

Results: even neutron rich Sn isotopes

σ(γ,Xn) [mb] dσ/dE* [mb/MeV] (1n) (2n) (3n) σ(γ,Xn) [mb] E* [MeV] dσ/dE* [mb/MeV] E* [MeV] (1n) (2n) (3n) E* [MeV] σ(γ,Xn) [mb]

100 200 300 400 100 200 300 100 200 300 100 200 300 400 100 200 300 10 20 100 200 300 10 20 100 200 300 400 10 20

experimental Coulomb cross section photoneutron cross section

stabile nucleus (real photons) radioactive nucleus (virtual photons)

  • P. Adrich et al., PRL 95 (2005)132501

PDR

  • position: ~ 10 MeV
  • strength:

some % TRK Sumrule

  • accordance with

predictions GDR

  • no deviation from

systematics

theoretical Coulomb cross section 124Sn 130Sn 132Sn

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Konstanze Boretzky – Emmi workshop July 2010

Low-lying strength in 132Sn mass region

  • bserved in all isotopes

difference between even and odd isotopes due to neutron separation threshold location and unpaired neutrons

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Konstanze Boretzky – Emmi workshop July 2010

Low-lying strength in 132Sn mass region

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Konstanze Boretzky – Emmi workshop July 2010

Low-lying strength in 132Sn 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

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Konstanze Boretzky – Emmi workshop July 2010

2 4 6 8 10 12

130Sn

Σ BPDR(E1)/Σ BGDR(E1) [ % ]

132Sn

0.15 0.2 0.25 0.3 0.35 1 2 3 4 5 6

130Sn

Rn-Rp [ fm ]

po [ MeV/fm3 ]

1 2 3 4 5 6

132Sn

po [ MeV/fm3 ]

Rn-Rp [fm]

Asymmetry parameters and neutron skins from experimental dipole response

  • A. Klimkiewicz, N. Paar et al.,

PHYSICAL REVIEW C 76, 051603(R) (2007)

< a4> = 32.0 ± 1.8 MeV Rn-Rp = 0.23 ± 0.04 fm Rn-Rp = 0.24 ± 0.04 fm < p0> = 2.3 ± 0.8 MeV/ fm3

ΣBPDR(E1)/ΣBGDR(E1) [%]

p0 [MeV/fm3] p0 [MeV/fm3] RQRPA calculations from

  • N. Paar
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Konstanze Boretzky – Emmi workshop July 2010

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)

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Konstanze Boretzky – Emmi workshop July 2010

208Pb analysis

a4 = 31.4 ± 0.8 MeV p0 = 2.1 ± 0.3 MeV / fm3 δr = 0.17 ± 0.02 fm ∑Bpdr(E1)=1.98 e2 fm2

from N.Ryezayeva et al., PRL 89(2002)272501

∑Bgdr(E1)=60.8 e2 fm2

from A.Veyssiere et al.,NPA 159(1970)561

RQRPA- N.Paar RQRPA- N.Paar RQRPA- N.Paar

  • ur

approach

M.Csatlos et al. NPA 719(2003)C304 A.Krasznahorkay et al. NPA 567(1994)521 C.J.Batty et al. Adv.Nucl.Phys. (1989)1 B.C. Clark et al. PRC 67(2003)044306

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Konstanze Boretzky – Emmi workshop July 2010

new contributions/contradictions

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Konstanze Boretzky – Emmi workshop July 2010

new contributions/contradictions

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Konstanze Boretzky – Emmi workshop July 2010

  • pen 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 32Ar experiment – under analysis

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Konstanze Boretzky – Emmi workshop July 2010

Isovector and isoscalar electric dipole and quadrupole response of neutron-rich Sn nuclei

accepted proposal at GSI What is new?

  • adress 124Sn to 134Sn
  • 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 CD2 target
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Konstanze Boretzky – Emmi workshop July 2010

Coulombexcitation of 132Sn on Pb target at 300 and 600 AMeV

600 AMeV 300 AMeV E1 E2 E1 E2 2*105 events simulated extracted E2 strength

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Konstanze Boretzky – Emmi workshop July 2010

proton pygmy predictions

N.Paar et al., Phys.Rev.Lett. 94 (2005) 182501 ≈ 6 % EWSR

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Konstanze Boretzky – Emmi workshop July 2010

Dipole response studies in 32Ar and 34Ar

statistics expected: ~500 events in PDR region, ~1000 in GDR region ~150 events in PDR region, ~1500 in GDR region

32Ar 34Ar

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Konstanze Boretzky – Emmi workshop July 2010

The LAND-FRS Collaboration

127-132Sn (Exp. S221) – 57-72Ni (Exp. S287)