1. Norbert Pietralla TU Darmstadt1 1. Feb. 2010 Current Themes of Nuclear Research and how the ELI photonuclear pillar could contribute to them Norbert Pietralla Director Institut für Kernphysik Darmstadt University of Technology (TUD) Collaborative Research Center SFB634 Research Center of Excellence Nuclear and Radiation Physics TUD Exploring nuclei with lasers

2. Norbert Pietralla TU Darmstadt2 1. Feb. 2010 Vision of Nuclear Physics Understanding the properties of heavy atomic nuclei quantitatively and predictably from their basic constituents, quarks and gluons, and from the interactions between them.

3. Norbert Pietralla TU Darmstadt3 1. Feb. 2010 Recent Progress Systematic derivation of structural form of nucleon- nucleon interaction from QCD in Chiral Perturbation Theory Unique low-energy NN-potential V low-k from Renormalization Group approach Non-perturbative all-order calculations from self- consistent iteration methods for nuclear many-body systems Advanced many-body techniques, e.g., No-Core Shell Model, Monte-Carlo Shell Model,…

4. Norbert Pietralla TU Darmstadt4 1. Feb. 2010 But still… Present theory still needs phenomenology for quantitative reliability Phenomenology requires input from data The less is known, the worse does theory Quest for „extreme“ conditions…

5. Relevant nuclear themes e.g. Nuclear Structure and Astrophysics Relevance for Astrophysics

6. Norbert Pietralla TU Darmstadt6 1. Feb. 2010 Central Topics for Nuclear Structure Halos Neutron Skins Neutron stars Pygmy Resonance EOS Quest for the limits of existence Halos, Open Quantum Systems, Few Body Correlations Changing shell structure far away from stability Skins, new collective modes, nuclear matter, neutron stars Phases and symmetries of the nuclear many body system Origin of the elements  unified theory (ab-initio, density functional, shell model)

7. Norbert Pietralla TU Darmstadt7 1. Feb. 2010 Outline Nuclear physics with low-energy photons (nuclear dipole physics) ELI day 1:  „Exploring the weakly bound“ Measurements near separation threshold  „Exploring the unknown“ Highest resolution (eV / MeV)-spectroscopy  „Exploring the dangerous“ radioactive-waste management (multi-billion $ market) Summary

8. Norbert Pietralla TU Darmstadt8 1. Feb. 2010 Photonuclear Physics with MeV-range photon beams Pure EM-interaction (nuclear-) model independent “small“ cross sections, penetrating, thick targets Minimum projectile mass min. angular momentum transfer, spin-selective: dipole-modes Polarisation “Parity physics“

9. Norbert Pietralla TU Darmstadt9 1. Feb. 2010 Realm of photonuclear structure physics  Electric Dipole strength concentrated in GDR above and in PDR below particle separation threshold  Photonuclear reaction useful tool for investigation of dipole strength Energy / MeV 515 ( γ,γ ‘)( γ, n) Giant Dipole Resonance Pygmy- Dipol Resonance Two- Phonon- State SnSn x

10. Norbert Pietralla TU Darmstadt10 1. Feb. 2010 Photonuclear Reactions gs ´´  Separation threshold AXAX A´ Y  Nuclear Resonance Fluorescence (NRF) Photoactivation Photodisintegration  Absorption (-activation) ´´

11. Norbert Pietralla TU Darmstadt11 1. Feb. 2010

12. Norbert Pietralla TU Darmstadt12 1. Feb. 2010 HIgS Beam Profile N.Pietralla et al. Phys. Rev. Lett. 88 012502 (2002).

13. Norbert Pietralla TU Darmstadt13 1. Feb. 2010 Traditionally Bremsstrahlung: Kneissl,Pietralla,Zilges, J.Phys.G 32, R217 (2006).

14. Norbert Pietralla TU Darmstadt14 1. Feb. 2010 S-DALINAC facility at IKP TU Darmstadt 1 2 Photon Experiments 10 MeV Injector: Photon Scattering / Photofission < 30 MeV Tagger: Photodesintegration / Photon Scattering Source 130 MeV Electron LINAC Electron Source

15. Norbert Pietralla TU Darmstadt15 1. Feb. 2010 Darmstadt Low-Energy Photon Scattering Site at S-DALINAC Target Ge(HP)  -detectors Radiator target e-e-  Energie Intensity Electrons Energie Intensity Bremsstrahlung < 10 MeV Cu E  < 10 MeV Cu

16. Norbert Pietralla TU Darmstadt16 1. Feb. 2010 Spectroscopy near separation threshold

17. Norbert Pietralla TU Darmstadt17 1. Feb. 2010 A. Zilges et al., PLB 542 (2002) 43. S. Volz et al., NPA 779 (2006) 1. U. Kneissl, NP et al., J.Phys.G 32, R217 (2006). Systematics of the Pygmy Dipole Resonance Concentration around 5-7 MeV Strong fragmentation Summed strength: Scaling with N/Z ? Mass dependence of  -ray strength function ? skin core

18. Norbert Pietralla TU Darmstadt18 1. Feb. 2010  aim: determination of transition strengths: need absolute values for ground state transition width  NRF-experiments give product with branching ratio:  assumption:  no transition in low-lying states observed  but: many small branchings in other states?  self-absorption: measurement of absolute ground state transition widths eV-resolving spectroscopy with photon beams

19. Norbert Pietralla TU Darmstadt19 1. Feb. 2010 Principle of Self-Absorption absorber nuclei: photons of decay processes: E0E0 EfEf EjEj JfJf JjJj J0J0 Γ j0 Γ fj Γ0Γ0 Γ0Γ0 Γ0Γ0 e Absorber

20. Norbert Pietralla TU Darmstadt20 1. Feb. 2010 Interaction within the absorber atomic attenuation mainly Compton effect Klein-Nishina formula resonance absorption depends on Γ 0 Doppler cross section

21. Norbert Pietralla TU Darmstadt21 1. Feb. 2010 Photon flux density after absorption

22. Norbert Pietralla TU Darmstadt22 1. Feb. 2010 problem: resolution of modern detectors by far too low solution: scattering target made of same material as absorber is highly resolving detector (same resonances → sensitive on change in photon flux) two measurements: one w/ and one w/o absorber scatterer bremsstrahlung radiator calibrator electrons absorber absorber spectrum detector self-absorption: decrease of decays in scatterer because of resonant absorption Principle of Self-Absorption

23. Norbert Pietralla TU Darmstadt23 1. Feb. 2010 Measuring principle II

24. Norbert Pietralla TU Darmstadt24 1. Feb. 2010 Recent results ( 140 Ce) scatterer: 2 g 140 Ce calibrator: 312 mg 11 B absorber: 60 g CeO 2 endpoint energy: 8 MeV measuring time: in each case about 4 days Photon flux: 10 3  /(s eV cm 2 )

25. Norbert Pietralla TU Darmstadt25 1. Feb. 2010 Determine ground state transition width Γ 0 self-absorption R can be calculated analytically it depends on K and thus on reminder: determine self-absorption experimentally and compare with calculation

26. Norbert Pietralla TU Darmstadt26 1. Feb. 2010 Test of „the branching Assumption“ Γ 0 /Γ ≈ 1 Access to  -ray strength function green line: branching ratio into ground state is = 1 branching ratio can‘t be larger than 1 – points have to lie above green line two transitions with small branching into ground state (large errros) many points agree with green line one point clearly underneath green line – not one strong but two weaker transitions of close lying states?!

27. Norbert Pietralla TU Darmstadt27 1. Feb. 2010 Potential for ELI photonuclear pillar‘s high-flux high-resolution  -ray beam Improvement by 3 orders of magnitude in photon flux is feasible Will open up new horizons for photonuclear research  Nuclear dipole strength near threshold  Fine structure of quadrupole response  Energy resolution on Doppler-width scale  Detection of hazardous material in bulk matter  New approaches…

28. Norbert Pietralla TU Darmstadt28 1. Feb. 2010 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 should be possible at ELI !

29. Norbert Pietralla TU Darmstadt29 1. Feb. 2010 Thank you !

30. Norbert Pietralla TU Darmstadt30 1. Feb. 2010 Parity Measurements Principle of a Compton-Polarimeter

31. Norbert Pietralla TU Darmstadt31 1. Feb. 2010 Modest polarisation sensitivity Better use polarized  -ray beams !

32. Norbert Pietralla TU Darmstadt32 1. Feb. 2010 Azimuthal asymmetry → parity quantum no. Parity Measurements with Linearly Polarized Photon Beams

33. Norbert Pietralla TU Darmstadt33 1. Feb. 2010

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35. Norbert Pietralla TU Darmstadt35 1. Feb. 2010

36. Norbert Pietralla TU Darmstadt36 1. Feb. 2010

37. Norbert Pietralla TU Darmstadt37 1. Feb. 2010

38. Norbert Pietralla TU Darmstadt38 1. Feb. 2010 Testing shell structure from M1 Spin-flip excitation

39. Norbert Pietralla TU Darmstadt39 1. Feb. 2010

40. Norbert Pietralla TU Darmstadt40 1. Feb. 2010 40Ar First observation of a 1 + state of 40 Ar

41. Norbert Pietralla TU Darmstadt41 1. Feb. 2010 Duke-Stony Brook expt. high-pressure Ar gas HIgS polarized g-beam 7.7 MeV < E < 11 MeV analyzing power 50% Duke – Stony Brook data (2 examples)

42. Norbert Pietralla TU Darmstadt42 1. Feb. 2010 T.C.Li, NP et al, Phys.Rev.C (2006).

43. Norbert Pietralla TU Darmstadt43 1. Feb. 2010 Astrophysical Relevance of M1 Data Darmstadt data 54 Fe Langanke et al., PRL (2004). Neutrino-cross sections

44. Norbert Pietralla TU Darmstadt44 1. Feb. 2010 Direct Measurement of B(GT) from Charge-Exchange Reactions Osaka-data Fujita et al., PRL(2005). Adachi et al.,PRC (2006).

45. Norbert Pietralla TU Darmstadt45 1. Feb. 2010 Polarized Beams 100 keV Polarized Electron Gun 5 m Spatial restriction – transport of accelerator equipment 10 MeV Injector 250 keV Thermionic Electron Gun To Experimental Hall

46. Norbert Pietralla TU Darmstadt46 1. Feb. 2010

47. Norbert Pietralla TU Darmstadt47 1. Feb. 2010

48. Norbert Pietralla TU Darmstadt48 1. Feb. 2010 Preparation system Polarized electron gun Differential pumping stages Injector cryostat Prebuncher system Chopper Mott polarimeter Wien filter 1 m S-DALINAC Polarized INjector (SPIN) From Gun Laser Red Hall Entrance Thermionic electron gun Injector cryostat 2 m  Design of polarized injector beam line finished (Prof.Dr.J.Enders)  Installation begins – middle of January 2010

49. Norbert Pietralla TU Darmstadt49 1. Feb. 2010 Polarization in the entrance channel Linear polarization (HI  S) spin/parity program (since 2001) Circular polarization (HI  S, S-DALINAC) parity non-conservation 20 Ne, 238 U EE bremsstrahlung spectrum NN P  ≤ 75% e-e- target  circular bremstarget -θ-θ θ Forward-backward asymmetry ? Parity-violation Weak interaction

50. Norbert Pietralla TU Darmstadt50 1. Feb. 2010 Polarization in the entrance channel Linear polarization (HI  S) spin/parity program (since 2001) Circular polarization (HI  S, S-DALINAC) parity non-conservation 20 Ne, 238 U target  circular -θ-θ θ Forward-backward asymmetry ? Parity-violation Weak interaction

51. Norbert Pietralla TU Darmstadt51 1. Feb. 2010 The 20 Ne case: parity mixing of yrast levels ΔE=7.5±5.7 keV “enhancement factor” 670 ± 7000 Γ(1 - ) ≤ 0.3 keV Γ(1 + ) ? T < =0 1+1+ 1-1- 11270±5 11262±3 20 Ne 0+0+ 20 F, T < = 1 1-1- 1+1+ 3+3+ 4+4+ 5+5+ 2+2+  (d 5/2 1 ) (d 5/2 3 ) gs 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 20 Ne !

52. Norbert Pietralla TU Darmstadt52 1. Feb. 2010 Heavy Atomic nucleus many-body system consists of two equivalent entities (protons-neutrons) quantum system COLLECTIVITY SHELL STRUCTURE ISOSPIN SYMMETRY Two-fluid quantum system Generic Aspects of Nuclear Structure Coexist, interplay, and compete? Study collective proton-neutron valence shell excitations ! (combine all 3 aspects)

53. Norbert Pietralla TU Darmstadt53 1. Feb. 2010 Themes and challenges of Modern Science Complexity out of simplicity How the world, with all its apparent complexity and diversity can be constructed out of a few elementary building blocks and their interactions Simplicity out of complexity How the world of complex systems can display such astonishing regularity and simplicity Understanding the nature of the physical universe Manipulating nature for the benefit of mankind Nuclei: Two-fluid, many-body, strongly-interacting, quantal systems provide wonderful laboratories for frontier research in all four areas From US-NSAC-charge: “Nuclear Physics with the Rare Isotope Accelerator”

54. Norbert Pietralla TU Darmstadt54 1. Feb. 2010 Die Valenz-Proton-Neutron Wechselwirkung Bestimmt die Entwicklung von Kollektivitaet und Kerndeformation Bildet die mikroskopische Grundlage fuer Deformations- Phasen-Uebergangsverhalten (Federman-Pittel Mechanismus) Bewirkt Besetzungszahlabhaengigkeit von Einteilchen- Energien, Energieluecken und Schalenstruktur

55. Norbert Pietralla TU Darmstadt55 1. Feb. 2010 Relevance Deductive understanding of Nature Solid understanding of the nucleus as a laboratory for other fields (standard model, neutrino physics, strongly interacting many-body Fermi-systems…) Dynamics of cosmic objects and the “Origin of the Elements“ (astrophysics, nuclear astrophysics)

56. Norbert Pietralla TU Darmstadt56 1. Feb. 2010 shell structure: valence nucleons Cooper pairing: N s,d boson system Collective motion: nuclear shapes Once the atomic nucleus is formed effective (in-medium) forces can generate simple pattern.

57. Norbert Pietralla TU Darmstadt57 1. Feb. 2010 Nucleon-Spin-flip Role of Isovector Spin-flip M1 excitations in Nuclear Physics E (MeV) Quark-Spin-flip

58. Norbert Pietralla TU Darmstadt58 1. Feb. 2010 Overview: dipole modes Exotic Modes B(M1) Orbital M1 Strength Scissors mode,… Spin M1 Strength

59. Norbert Pietralla TU Darmstadt59 1. Feb. 2010 Electric Giant Dipol Resonance (GDR) Protons Neutrons Sensitive to average Proton-Neutron-Restoring Force but insensitive to shell structure: need low-energy E1/M1 data ! GDR in 197 Au GDR-Strength vs A Data from: A.Bohr, B.Mottelson “Nuclear Structure” E1

60. Norbert Pietralla TU Darmstadt60 1. Feb. 2010 Scissors Mode in Deformed Nuclei (Darmstadt, 1983) Bohle et al., NPA 458, 205 (1986). Scissors mode classically: current loop => M1 magnetic dipole excitation electron scattering photon scattering

61. Norbert Pietralla TU Darmstadt61 1. Feb. 2010 Richter, Kneissl, von Brentano et al. Collectivity of the Scissors Mode M1 phenomena in the nuclear valence shell E2M1 Measure of quadrupole collectivity 2+2+ Stuttgart-Darmstadt-Köln 1+1+ N. Pietralla et al., PRC 58, 184 (1998)

62. Norbert Pietralla TU Darmstadt62 1. Feb. 2010 MSSs* at the analytical Limits N  = N =1 0+0+ 2+2+ 4+4+ 0+0+ 2+2+ SU(3) Rotor 2+2+ 3+3+ 1+1+ Scissors Mode N.Pietralla et al. Univ.zu Koeln, 1999 K=1 0+0+ 4+4+ 2+2+ 0+0+ 2+2+ 2+2+ 1+1+ 3+3+ U(5) Vibrator F max -1 MS multi-Phonon structure A. Richter et al. TU Darmstadt, 1983 * MSSs = proton-neutron Mixed-Symmetry States

63. Norbert Pietralla TU Darmstadt63 1. Feb. 2010 Proton-Neutron symmetrische und gemischt-symmetrische Valenzraumanregungen (schematisch/geometrisch) Sphaerischer Kern Vibration Deformierter Kern Rotation Protonen-Neutronen ausser Phase Gem.-sym. Vibration Protonen-Neutronen ausser Phase Scherenmode Animation: Robert Casperson (Yale)