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Nuclear Structure Physics at 4GLS

SFB634. Collaborative Research Center. TUD. Research Center of Excellence Nuclear and Radiation Physics. Nuclear Structure Physics at 4GLS. Norbert Pietralla Institut für Kernphysik Darmstadt University of Technology TUD. Vision of Nuclear Physics.

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Nuclear Structure Physics at 4GLS

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  1. SFB634 Collaborative Research Center TUD Research Center of Excellence Nuclear and Radiation Physics Nuclear Structure Physics at 4GLS Norbert Pietralla Institut für Kernphysik Darmstadt University of Technology TUD Professor Dr. Norbert Pietralla TU Darmstadt

  2. Vision of Nuclear Physics Understanding the properties of heavy atomic nuclei from their basic constituents, quarks and gluons, and from the interactions between them. Professor Dr. Norbert Pietralla TU Darmstadt

  3. 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) Professor Dr. Norbert Pietralla TU Darmstadt

  4. Recent Progress • Systematic derivation of structural form of nucleon-nucleon interaction from QCD in Chiral Perturbation Theory • Unique low-energy NN-potential Vlow-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,… Professor Dr. Norbert Pietralla TU Darmstadt

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

  6. 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 • Research potential of -ray beams from Laser Compton Backscattering • Summary Professor Dr. Norbert Pietralla TU Darmstadt

  7. Nuclear Structure Physics with low-energy 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“ Professor Dr. Norbert Pietralla TU Darmstadt

  8. Nucleon-Spin-flip Role of Isovector Spin-flip M1 excitations in Nuclear Physics E (MeV) Quark-Spin-flip Professor Dr. Norbert Pietralla TU Darmstadt

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

  10. Separation threshold  ´ ´  A´Y  Photonuclear Reactions Absorption gs AX Nuclear Resonance Fluorescence (NRF) Photoactivation Photodesintegration (-activation) Professor Dr. Norbert Pietralla TU Darmstadt

  11. Traditionally Bremsstrahlung: Kneissl,Pietralla,Zilges, J.Phys.G 32, R217 (2006). Professor Dr. Norbert Pietralla TU Darmstadt

  12. Overview: dipole modes Spin M1 Strength Exotic Modes Orbital M1 Strength Scissors mode,… B(M1) Professor Dr. Norbert Pietralla TU Darmstadt

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

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

  15. Ge(HP) g-detectors Target g e- Radiator target Electrons Bremsstrahlung Intensity Intensity Energie Energie Darmstadt Low-Energy Photon Scattering Site at S-DALINAC A.Zilges E < 10 MeV Cu Cu < 10 MeV Professor Dr. Norbert Pietralla TU Darmstadt

  16. Professor Dr. Norbert Pietralla TU Darmstadt

  17. 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 ? A. Zilges et al., PLB 542 (2002) 43. S. Volz et al., NPA 779 (2006) 1. A. Zilges, contrib. to Vico Equense 07. Professor Dr. Norbert Pietralla TU Darmstadt

  18. Parity Measurements Principle of a Compton-Polarimeter Professor Dr. Norbert Pietralla TU Darmstadt

  19. Modest polarisation sensitivity Better use polarized -ray beams ! Professor Dr. Norbert Pietralla TU Darmstadt

  20. Parity Measurements with Linearly Polarized Photon Beams Azimuthal asymmetry → parity quantum no. Professor Dr. Norbert Pietralla TU Darmstadt

  21. Professor Dr. Norbert Pietralla TU Darmstadt

  22. Professor Dr. Norbert Pietralla TU Darmstadt

  23. Professor Dr. Norbert Pietralla TU Darmstadt

  24. Professor Dr. Norbert Pietralla TU Darmstadt

  25. Professor Dr. Norbert Pietralla TU Darmstadt

  26. Professor Dr. Norbert Pietralla TU Darmstadt

  27. HIgS Beam Profile Professor Dr. Norbert Pietralla TU Darmstadt

  28. Testing shell structure from M1 Spin-flip excitation Professor Dr. Norbert Pietralla TU Darmstadt

  29. First ever observation of a 1+ state of 40Ar 40Ar Professor Dr. Norbert Pietralla TU Darmstadt

  30. T.C.Li, NP et al, Phys.Rev.C (2006). Professor Dr. Norbert Pietralla TU Darmstadt

  31. Astrophysical Relevance of M1 Data Langanke et al., PRL (2004). Neutrino-cross sections Darmstadt data 54Fe Professor Dr. Norbert Pietralla TU Darmstadt

  32. Direct Measurement of B(GT) from Charge-Exchange Reactions Osaka-data Fujita et al., PRL(2005). Adachi et al.,PRC (2006). Professor Dr. Norbert Pietralla TU Darmstadt

  33. g e- -θ θ Pg≤ 75% bremsstrahlung spectrum Ng Eg • Polarization in the entrance channel • Linear polarization (HIS) • spin/parity program (since 2001) • Circular polarization (HIS, S-DALINAC) • parity non-conservation • 20Ne, 238U bremstarget target Forward-backward asymmetry ? Parity-violation Weak interaction circular Professor Dr. Norbert Pietralla TU Darmstadt

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

  35. Generic Aspects of Nuclear Structure Heavy Atomic nucleus Two-fluid quantum system • many-body system • COLLECTIVITY • quantum system • SHELL STRUCTURE • consists of two equivalent entities (protons-neutrons) • ISOSPIN SYMMETRY Coexist, interplay, and compete? Study collective proton-neutron valence shellexcitations ! (combine all 3 aspects) Professor Dr. Norbert Pietralla TU Darmstadt

  36. From US-NSAC-charge: “Nuclear Physics with the Rare Isotope Accelerator” • 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 Professor Dr. Norbert Pietralla TU Darmstadt

  37. Summary • Nuclear structure physics with -ray beams is a vivid field with high discovery potential • 4GLS can become a major facility in this field • Needs: - energy-tunable, high-flux, polarized -ray beam from LASER-Compton backscattering • All this is possible at 4GLS ! Professor Dr. Norbert Pietralla TU Darmstadt

  38. Professor Dr. Norbert Pietralla TU Darmstadt

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