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

Professor Dr. Norbert Pietralla TU Darmstadt 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

Professor Dr. Norbert Pietralla TU Darmstadt 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

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 Collective motion: nuclear shapes Professor Dr. Norbert Pietralla TU Darmstadt

Professor Dr. Norbert Pietralla TU Darmstadt 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

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

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

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 ! Professor Dr. Norbert Pietralla TU Darmstadt Data from: A.Bohr, B.Mottelson “Nuclear Structure”

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

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

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

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

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) Professor Dr. Norbert Pietralla TU Darmstadt

S-DALINAC facility at IKP TU Darmstadt 1 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 Professor Dr. Norbert Pietralla TU Darmstadt

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

Professor Dr. Norbert Pietralla TU Darmstadt

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 ? 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

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

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

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

Professor Dr. Norbert Pietralla TU Darmstadt

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

Professor Dr. Norbert Pietralla TU Darmstadt 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) Professor Dr. Norbert Pietralla TU Darmstadt

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

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

250 keV Thermionic Electron Gun Polarized Beams 100 keV Polarized Electron Gun 250 keV Thermionic Electron Gun 10 MeV Injector To Experimental Hall 5 m Spatial restriction – transport of accelerator equipment Professor Dr. Norbert Pietralla TU Darmstadt

S-DALINAC Polarized INjector (SPIN) Preparation system Polarized electron gun Differential pumping stages Injector cryostat Prebuncher system Chopper Mott polarimeter Wien filter 1 m Red Hall Entrance Thermionic electron gun Injector cryostat 2 m From Gun Laser Design of polarized injector beam line finished (Prof.Dr.J.Enders) Installation begins – middle of 2007 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 20Ne, 238U bremstarget target e- g Forward-backward asymmetry ? Parity-violation Weak interaction circular -θ θ Eg bremsstrahlung spectrum Ng Pg ≤ 75% Professor Dr. Norbert Pietralla TU Darmstadt

The 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 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

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, quantal systems provide wonderful laboratories for frontier research in all four areas Professor Dr. Norbert Pietralla TU Darmstadt

Professor Dr. Norbert Pietralla TU Darmstadt 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

Professor Dr. Norbert Pietralla TU Darmstadt

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 Professor Dr. Norbert Pietralla TU Darmstadt

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

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