Nuclear Structure Physics at 4 GLS Norbert Pietralla
Nuclear Structure Physics at 4 GLS Norbert Pietralla SFB 634 Collaborative Research Center TUD Institut für Kernphysik Darmstadt University of Technology Research Center of Excellence Nuclear and Radiation Physics TUD Professor Dr. Norbert Pietralla TU Darmstadt
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
Relevance n Deductive understanding of Nature n Solid understanding of the nucleus as a laboratory for other fields (standard model, neutrino physics, strongly interacting many -body Fermi-systems…) n Dynamics of cosmic objects and the “Origin of the Elements“ (astrophysics, nuclear astrophysics) Professor Dr. Norbert Pietralla TU Darmstadt
Recent Progress n Systematic derivation of structural form of nucleon-nucleon interaction from QCD in Chiral Perturbation Theory n Unique low-energy NN-potential Vlow-k from Renormalization Group approach n Non-perturbative all-order calculations from selfconsistent iteration methods for nuclear manybody systems n Advanced many-body techniques, e. g. , No-Core Shell Model, Monte-Carlo Shell Model, … Professor Dr. Norbert Pietralla TU Darmstadt
Once the atomic nucleus is formed effective (in-medium) forces can generate simple pattern. shell structure: valence nucleons Cooper pairing: N s, d boson system Professor Dr. Norbert Pietralla TU Darmstadt Collective motion: nuclear shapes
Outline n Nuclear physics with low-energy photons (nuclear dipole physics) n Impact of photon beams from Laser Compton Backscattering ¨ Recent progress at Duke‘s HI S potential of -ray beams from Laser Compton Backscattering ¨ Research n Summary Professor Dr. Norbert Pietralla TU Darmstadt
Nuclear Structure Physics with low-energy photon beams n Pure EM-interaction (nuclear-) model independent “small“ cross sections, thick targets n Minimum projectile mass min. angular momentum transfer, -selective: dipole-modes n Polarisation “Parity physics“ Professor Dr. Norbert Pietralla TU Darmstadt spin
Role of Isovector Spin-flip M 1 excitations in Nuclear Physics E (Me. V) Quark-Spin-flip Nucleon-Spin-flip Professor Dr. Norbert Pietralla TU Darmstadt
Electric Giant Dipol Resonance (GDR) E 1 GDR in 197 Au GDR-Strength vs A Protons Neutrons Sensitive to average Proton-Neutron-Restoring Force but insensitive to shell structure: need low-energy E 1/M 1 data ! Professor Dr. Norbert Pietralla TU Darmstadt Data from: A. Bohr, B. Mottelson “Nuclear Structure”
Photonuclear Reactions Absorption Separation threshold ´ gs AX ´ A´Y Nuclear Resonance Fluorescence (NRF) Photoactivation Photodesintegration (-activation) Professor Dr. Norbert Pietralla TU Darmstadt
Traditionally Bremsstrahlung: Kneissl, Pietralla, Zilges, J. Phys. G 32, R 217 (2006). Professor Dr. Norbert Pietralla TU Darmstadt
Overview: dipole modes Exotic Modes Spin M 1 Strength Orbital M 1 Strength Scissors mode, … B(M 1) Professor Dr. Norbert Pietralla TU Darmstadt
Scissors Mode in Deformed Nuclei (Darmstadt, 1983) Scissors mode classically: current loop => M 1 magnetic dipole excitation electron scattering photon scattering Bohle et al. , NPA 458, 205 (1986). Professor Dr. Norbert Pietralla TU Darmstadt
S-DALINAC facility at IKP TU Darmstadt i 1 Source Electron Source 130 Me. V Electron LINAC Photon Experiments 1 10 Me. V Injector: Photon Scattering / Photofission 2 < 30 Me. V Tagger: Photodesintegration / Photon Scattering Professor Dr. Norbert Pietralla TU Darmstadt 2
Darmstadt Low-Energy Photon Scattering Site at S-DALINAC < 10 Me. V Ge(HP) Cu -detectors Cu Target e- Energie Intensity Radiator target Electrons A. Zilges E < 10 Me. V Bremsstrahlung Energie Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Systematics of the Pygmy Dipole Resonance • Concentration around 5 -7 Me. V • Strong fragmentation • Summed strength: Scaling with N/Z ? Is this really all E 1 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
Parity Measurements Principle of a Compton-Polarimeter Professor Dr. Norbert Pietralla TU Darmstadt
Modest polarisation sensitivity Better use polarized -ray beams ! Professor Dr. Norbert Pietralla TU Darmstadt
Parity Measurements with Linearly Polarized Photon Beams Azimuthal asymmetry → parity quantum no. Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
HIg. S Beam Profile Professor Dr. Norbert Pietralla TU Darmstadt
Testing shell structure from M 1 Spin-flip excitation Professor Dr. Norbert Pietralla TU Darmstadt
First ever observation of a 1+ state of 40 Ar Professor Dr. Norbert Pietralla TU Darmstadt
T. C. Li, NP et al, Phys. Rev. C (2006). Professor Dr. Norbert Pietralla TU Darmstadt
Astrophysical Relevance of M 1 Data Langanke et al. , PRL (2004). Neutrino-cross sections Darmstadt data 54 Fe Professor Dr. Norbert Pietralla TU Darmstadt
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
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 bremstarget e- Forward-backward asymmetry ? Parity-violation circular -θ bremsstrahlung spectrum N target θ P ≤ 75% E Weak interaction Professor Dr. Norbert Pietralla TU Darmstadt
The 20 Ne case: parity mixing of p(d )n(d ) yrast levels 1 5/2 Γ(1+) ? isobaric analog states 1+ 11270± 5 1 - 11262± 3 T=1 Γ(1 -) 3 5/2 5+ 1 - ≤ 0. 3 ke. V 1+ 2+ 20 F, + 3+ 4 gs T< = 1 ΔE=7. 5± 5. 7 ke. V “enhancement factor” 670 ± 7000 Understand effects of weak interaction microscopically 20 Ne 0+ Goal: measure parity violation in simple states ! T<=0 ► e. g. , study the parity doublet in 20 Ne ! Professor Dr. Norbert Pietralla TU Darmstadt
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 shell excitations ! (combine all 3 aspects) Professor Dr. Norbert Pietralla TU Darmstadt
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, Professor Dr. Norbert Pietralla quantal systems provide TU Darmstadt wonderful laboratories for frontier research in all four areas
Summary Nuclear structure physics with -ray beams is a vivid field with high discovery potential n 4 GLS can become a major facility in this field n Needs: - energy-tunable, high-flux, polarized -ray beam from LASERCompton backscattering n All this is possible at 4 GLS ! n Professor Dr. Norbert Pietralla TU Darmstadt
Professor Dr. Norbert Pietralla TU Darmstadt
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