1. ELI & FAIR: A Natural Pair Nuclear Structure w
ELI & FAIR: A Natural Pair Nuclear Structure w. Photon Beams Norbert Pietralla, TU Darmstadt
DAAD
BMBF
DAAD
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

2. Outline
Nuclear physics with low-energy photons (nuclear dipole physics)
Impact of photon beams from Laser Compton Backscattering
Recent progress at Duke‘s HIS
Proof of Principle: 32S
Pygmy Dipole Resonance: 138Ba
Spin-Orbit Splitting: 40Ar
Weak Coupling of Single Particles: 207Pb
Parity Doublet : 20Ne
Research potential of -ray beams from Laser Compton Backscattering
Summary
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

3. Nuclear Physics with MeV-range photon beams
Pure EM-interaction
(nuclear-) model independent
“small“ cross sections, thick targets
Minimum projectile mass
min. angular momentum transfer, spin-selective: dipole-modes
Polarisation
„Parity Physics“
Narrow Bandwidth (at ELI)
„Selective Manipulation of Nuclear States“
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

4. Role of Isovector Spin-flip M1 excitations in Nuclear Physics
(MeV)
Nucleon-Spin-flip
Quark-Spin-flip
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

5. Induced 3N-Interaction in EFT
Isovector M1 excitation of 48Ca
Vlow-k interaction
3N-forces from EFT
SPEs self-consistently calculated in many-body perturbation theory
S-DALINAC data
J.Holt, A.Schwenk et al., subm. to PRL
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

6. Electric Giant Dipol Resonance (GDR)
Protons
Neutrons E1
GDR in 197Au
GDR-Strength vs A
Sensitive to average Proton-Neutron-Restoring Force
but insensitive to shell structure: need low-energy E1/M1 data !
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
Data from: A.Bohr, B.Mottelson “Nuclear Structure”

7. E1 Strength Distribution
Energy/MeV
Strength 5 10 15
GDR
Pygmy
Quadrupol/Oktupol
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

8. Photonuclear Reactions
Separation
threshold
Absorption ´  ´ 
A´Y  gs AX
Nuclear Resonance Fluorescence (NRF)
Photoactivation
Photodisintegration
(-activation)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

9. Traditionally Bremsstrahlung: Kneissl,Pietralla,Zilges, J. Phys
Traditionally Bremsstrahlung: Kneissl,Pietralla,Zilges, J.Phys.G 32, R217 (2006).
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

10. Scissors Mode of Deformed Nuclei (A.Richter, Darmstadt, 1983)
classically: current loop => M1
magnetic dipole excitation
electron scattering
photon scattering
Bohle et al., NPA 458, 205 (1986).
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

11. M1 phenomena in the nuclear valence shell
Collectivity of the Scissors Mode
Richter,
Kneissl,
von Brentano
et al.
Stuttgart-Darmstadt-Köln
Measure of quadrupole
collectivity 1+ 2+ E2 M1
N. Pietralla et al., PRC 58, 184 (1998)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

12. S-DALINAC at TU Darmstadt1 2 i 1 2
Photon Experiments
10 MeV Injector: Photon Scattering / Photofission
< 30 MeV Tagger: Photodesintegration / Photon Scattering
Source
130 MeV Electron LINAC
Electron Source
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

13. Darmstadt Low-Energy Photon Scattering Site at S-DALINAC
Ge(HP)
g-detectors Cu Cu
< 10 MeV
Target g e-
Radiator target
Electrons
Bremsstrahlung
E < 10 MeV
Intensity
Intensity
Energie
Energie
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

14. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

15. Is this really all E1 strength ?
Systematics of the Pygmy Dipole Resonance
Concentration
around 5-7 MeV
Strong fragmentation
Summed strength: Scaling with N/Z ?
Is this really all E1 strength ?
core
skin
A. Zilges et al., PLB 542 (2002) 43.
S. Volz et al., NPA 779 (2006) 1.
U. Kneissl et al., J.Phys.G 32, R217 (2006).
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

16. Polarimetry with linearly polarized photon beams
Scattering intensity
distribution for linearly
polarized photons
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

17. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

18. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

19. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

20. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

21. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

22. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

23. HIS Beam Profile; Parity of Pygmy Resonance
HIS data
138Ba
Polarized photon beam
HIS 2002
Compton-polarimeter
EUROBALL Cluster 1999
N. Pietralla et al. Phys. Rev. Lett. 88, (2002)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

24. Testing shell structure from M1 Spin-flip excitation
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

25. Proton Spin-Orbit Force near 40Ca
p-n are in different shells
“Otsuka mechanism”
40Ar
HIS data
40Ar
T.C.Li, NP et al. Phys. Rev. C 73, (2006).
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

26. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

27. Astrophysical Relevance of M1 Data
Langanke et al., PRL (2004).
Neutrino-cross sections
Darmstadt data
54Fe
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

28. Collective Valence-Shell Structures
Two-Phonon Structures
quadrupole-octupole
symmetric/mixed-symmetric
92Zr
96Mo
HIS data
C. Fransen, NP et al., Phys. Rev. C 70, (2004)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

29. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

30. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

31. Testing single particle contributions to complex nuclear states
207Pb
HIS data
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

32. Polarization in the entrance channel
Parity Physics
Polarization in the entrance channel
Linear polarization (HIS)
spin/parity programme (since 2001)
Circular polarization (HIS, S-DALINAC)
parity non-conservation
20Ne
target g
circular
Forward-backward
asymmetry ?
Parity-violation
Weak interaction -θ θ
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

33. 20Ne case: parity mixing of yrast levels
20F, T< = 1 1- 1+ 3+ 4+ 5+ 2+
p(d5/21)n(d5/23) gs
ΔE=7.5±5.7 keV
“enhancement factor”
670 ± 7000
Γ(1-) ≤ 0.3 keV
Γ(1+) ? 1+ 1-
11270±5
11262±3
20Ne 0+
T=1
isobaric analog states
Goal: measure parity violation
in simple states !
Understand effects of weak interaction
microscopically
► e.g., study the parity doublet in 20Ne !
T<=0
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

34. 20Ne: Parity Mixing of Yrast States
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

35. 20Ne/28Si in linearly/circularly polarized γ-beam
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

36. 20Ne/28Si in linearly/circularly polarized γ-beam
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

37. HIS is unique and complementary Increased intensity
summary
New data: beam time Sept. 2007
203,205Tl
206,207,208Pb
40Ar
HIS is unique and complementary
Increased intensity
Strong nuclear Structure program: keep it well going !
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

38. Summary
Nuclear structure physics with -ray beams is a vivid field with high discovery potential
ELI can become a major facility in this field
Needs: energy-tunable, high-flux, high-rep.rate, high-resolution, polarized -ray beam from LASER-Compton backscattering
All this will be possible at ELI !
Future w. high Brightness: ELI & FAIR
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

39. Thank you !
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

40. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons

41. Importance of the Proton-Neutron Interaction
Occupation-number dependence of spe‘s
Dominant origin for shape-phase transition
Dominates evolution of collectivity and deformation
Study observables that are directly sensitive to the proton-neutron interaction in the valence shell !
Rick Casten‘s
Textbook
Read it!
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

42. Scissors mode of deformed nuclei
Darmstadt, 1983
Achim Richter
(γ, γ‘)
(e,e‘)
Predicted by
Lo Iudice & Palumbo, 1978
@ 3 MeV: Iachello, 1981 in IBM
Bohle et al., NPA 458, 205 (1986).
DALINAC data
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

43. 94Mo: the „hydrogen atom“ for MS structure
M1 as unique signature for MS states
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

44. Superconducting-DArmstadt LINear electron ACcelerator (S-DALINAC)
130 MeV in-house electron linac
TM010 -mode acceleration
„cw“ beam at 3 GHz („S“-band)
Ideal for nuclear structure studies
Thanks to
State of Hesse
TU Darmstadt
DFG
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

45. Electron and Proton Scattering on 94Mo
S-DALINAC data
O.Burda et al., Phys.Rev.Lett. 99, (2007)
One-phonon states are strongly excited in (e,e‘) and (p,p‘) scattering experiments
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

46. Ex „GQR“ Valence shell 2+p 2+ms 2+n 2+1 Conclusions Vmix
Understanding of transition densities requires configurations „beyond the valence shell“.
IBM (valence shell model) unable to predict behaviour of transition densities.
QPM serves here as „full theory“ (no effective charges,…).
IBM (valence shell model) can be considered „effective low-energy theory“ (effective interaction, effective charges,...).
Effective models possible because of clear separation of scales (~2 MeV vs. ~20 MeV).
„GQR“
Valence shell
2+p
2+ms
Vmix
2+n
2+1
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

47. Summary
Nuclear structure physics: exciting topic of quantum many-body physics
Theory developments: from solid QCD to effective nuclear theory
Key-role of pn-interaction for formation of collective structures
Proton-neutron mixed-symmetry states: sensitive to effective pn-interaction in the valence shell
Isovector character of MSS first measured directly from transition radii
New signature for pn-mixed-symmetry states
First firm observation of mixed-symmetry state in radioactive isotope
Experimental methods available for research with „rare isotope beams“
FAIR under construction
FAIR nuclear structure programme is starting right now (the students [and professors] can‘t wait…)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

48. Many Thanks… P.von Brentano, J.Jolie, Ch.Fransen (Köln)
T.Ahn, L.Coquard, T.Möller, G.Rainovski, Ch.Walz, O.Burda, P.von-Neumann-Cosel, M.Danchev, C.Stoyanov, D.Tarpanov
J.Wambach, V.Yu.Ponomarev, R.V.Jolos
P.Reiter (Köln), V.Werner,R.F.Casten (Yale)
J.Gerl, J.Leske, P.Boutachkov, E.Merchan, N.Goel, M.Reese, Ch.Stahl
B.Alikhani, O.Möller, A.Heinz, Ph.John, A.Givechev, N.Kurz, H.Schaffner
Many more PhD/M.Sc./B.Sc.-students for their enthusiasm
DAAD
BMBF
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

49. Summary
Nuclear structure physics: exciting topic of quantum many-body physics
Theory developments: from solid QCD to effective nuclear theory
Key-role of pn-interaction for formation of collective structures
Proton-neutron mixed-symmetry states: sensitive to effective pn-interaction in the valence shell
Isovector character of MSS first measured directly from transition radii
New signature for pn-mixed-symmetry states
First firm observation of mixed-symmetry state in radioactive isotope
Experimental methods available for research with „rare isotope beams“
FAIR under construction
FAIR nuclear structure programme is starting right now (the students [and professors] can‘t wait…)
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

50. Generic Aspects of Nuclear Structure: (and topic of this presentation)
Heavy Atomic nucleus
strongly coupled many-body system
consists of two equivalent entities (protons-neutrons)
quantum system
Two-fluid quantum system
COLLECTIVITY
ISOSPIN SYMMETRY
SHELL STRUCTURE
How do these features coexist, interplay, and compete?
What are the dominant mechanisms and forces?
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

51. Principle of a Compton-Polarimeter
Parity Measurements
Principle of a
Compton-Polarimeter
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

52. Modest polarisation sensitivity Better use polarized -ray beams !
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

53. 21. Oct. 2011 | Norbert Pietralla @ NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

54. Resolution Scale and Simple Pattern
shell structure:
interacting nucleons
Cooper pairing:
N s,d boson system
Collective motion:
nuclear shapes
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons

55. Identification of One- and Two-phonon MSSs
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

56. Evidence for common structure of MSSs
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons
7. Mai 2018 |

57. Isovector Giant Dipole Resonance (IVGDR)
Protons
Neutrons
Strength of IVGDR vs A
GDR in 197Au
Sensitive to average pn-restoring force
However, insensitive to shell structure
21. Oct | Norbert NuSTAR-week | Experiments with Real Photons