Nuclear Structure – Current Directions

1. Nuclear Structure – Current Directions A Thematic Overview R. F. Casten

2. Quarks and Gluons Early Universe Lattice QCD Critical Point? Temperature Tc Hadrons Color Super- Conductor ? Nuclei Neutron stars Net Baryon Density Nucleon

3. 100 Mean Field Models Collective models Shell Model(s) Effective Interactions 10 Microscopic Ab Initio (GFMC...) QCD Proton Number Bare Nucleon-Nucleon Interactions 1 Quark-Gluon Interactions 50 100 10 5 1 Neutron Number QCD Vacuum QCD Vacuum

4. Distance heavy nuclei Energy few body quarks gluons vacuum quark-gluon soup QCD nucleon QCD few body systems free NN force many body systems effective NN force The Nuclear Many-Body Problem Energy, Distance, Complexity radioactive beams electron scattering relativistic heavy ions

5. The study of nuclei is a forefront area of science that links the Standard Model, QCD phenomena, many-body systems, and the cosmos. Goal: a comprehensive description of nuclei and their reactions Nuclear structure and reactions go beyond nuclei per se: Understanding the quantum many-body problem at variousdistance/energy scales Testing the fundamental laws of nature Understanding stellar evolution and the origin of the elements Society (national security, energy, medicine…) Both theory and experiment are needed. The Nucleus: an integral part of nuclear science

6. QCD • Origin of NN interaction • Many-nucleon forces • Effective fields subfemto… nano… Complex Systems Giga… Cosmos femto… Physics of Nuclei Quantum many-body physics Nuclear Astrophysics • In-medium interactions • Symmetry breaking • Collective dynamics • Phases and phase transitions • Chaos and order • Dynamical symmetries • Structural evolution • Origin of the elements • Energy generation in stars • Stellar evolution • Cataclysmic stellar events • Neutron-rich nucleonic matter • Electroweak processes • Nuclear matter equation of state • How does complexity emerge from simple constituents? • How can complex systems display astonishing simplicities? How do nuclei shape the physical universe?

7. Nuclear Structure Theory Overarching goal: • This has been a lofty and ambitious goal in nuclear science for over fifty years • “Unified” does not mean that there is a single theoretical method that will work in all cases • Self-bound, two-component quantum many-fermion system • Complicated interaction based on QCD with at least two- and three-nucleon components • We seek to describe the properties of “nuclei” ranging from the deuteron to neutron stars To arrive at a comprehensive and unified microscopic description of all nuclei and low-energy reactions from the the basic interactions between the constituent protons and neutrons There is no “one size fits all” theory for nuclei, but all our theoretical approaches need to be linked by an underlying use of the constituents and the interactions between them

8. A new era in Nuclear Structure Physics The New Frontiersof Physics with Exotic Nuclei Terra incognita — huge gene pool of nuclei • Four Frontiers • Proton Rich Nuclei • Neutron Rich Nuclei • Heaviest Nuclei • Evolution of structure within these boundaries We can customize our system– fabricate “any” nucleus (designer nuclei)controlling the number of constituent protons and neutrons to isolate and amplify specific physics or interactions

9. Nuclear Input (experiment and theory) Masses and drip lines Nuclear reaction rates Weak decay rates Electron capture rates Neutrino interactions Equation of State Fission processes Supernova neutron-Star E0102-72.3 KS 1731-260 How does the physics of nuclei impact the physical universe? • What is the origin of elements heavier than iron? • How do stars burn and explode? • What is the nucleonic structure of neutron stars? X-ray burst p process s-process 4U1728-34 331 330 Frequency (Hz) r process 329 328 327 10 15 20 Time (s) rp process Nova Crust processes T Pyxidis stellar burning protons neutrons

10. 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 remarkable 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

11. Nuclear collective motion What is the origin of ordered motion of complex nuclei? Complex systems often display astonishing simplicities. Nuclei are no exception. How is it that a heavy nucleus, with hundreds of rapidly moving nucleons, can exhibit collective motion.

12. Two views of nuclear structure Single-particle motionBulk collective motion Single-particle excitations Macroscopic shape with residual interactions of nuclear matter Phonons — bosons Protons, neutrons — fermions j = half-integer (orbital + intrinsic) Pauli Principle: At most 2j + 1 particles in a given orbit

13. Microscopy, mean field, shell structure Ui Vij r = |ri - rj|  r  = nl , E = Enl H.O. E = ħ (2n+l) E (n,l) = E (n-1, l+2) E (2s) = E (1d) Clusters of levels  shell structure Pauli Principle (≤ 2j+1 nucleons in orbit with ang. mom. j)  magic numbers, inert cores, valence nucleons Many-body  few-body: each body counts. Addition of 2 neutrons in a nucleus with 150 can drastically alter structure

14. Independent Particle Motion(particles in a box) • Mottleson Importance of shell gaps, magic numbers, and shell structure is not just a matter of details but fundamental to our understanding of one of the most basic features of nuclei– independent particle motion. If we don’t understand the basic quantum levels of nucleons in the nucleus, we don’t understand nuclei. Many aspects: Changing magic numbers, intruder orbits, residual interactions, correlations, collectivity, binding (e.g., drip lines, superheavies), and regularities. Perhaps counter-intuitively, the emergence of specific forms of nuclear collectivity depends on independent particle motion (and the Pauli Principle).

15. Pairing (in nuclei and nuclear matter) Manifestations: Energy gaps in even-even nuclei; Compression of levels in odd-A nuclei Odd-even mass differences Moments of inertia and rotational motion Quenching of Coriolis coupling Structural evolution in an Ising context; H = Hsph + HColl: Sph.-Def. Competition Structural singularities in N = Z nuclei • Unique nuclear features: surface effects/finite size, kinds of Cooper pairs, • Essential for existence of weakly-bound nuclei; continuum scattering • Various density regimes of strength • Crucial for many-body dynamics, skin modes, pair localization • Connection to other fields (BECs, CSC)

16. p-n interactions Strongest along diagonal where highest p-n overlaps occur First direct correlation of empirical p-n interaction strengths with empirical growth rates of collectivity Empirical R4/2

17. Ab initio Configuration interaction Density Functional Theory Approaches to nuclear structure Roadmap Collective and Algebraic Models Theoretical approaches overlap and need to be bridged

18. Approaches to Nuclear Structure • Microscopic – Approximate solutions to real nuclei • Effective Interactions • Ab initio, No core, Monte Carlo • Density Functional Theory • Enormously complex, numerically intensive. However, revolutionary advances, greatly enhanced ability to predict wide variety of nuclei  promise of a comprehensive theory • Macroscopic – Exact solutions to ideal nuclei • Geometricsymmetries. Simple patterns, quantum nos., Selection rules • Analytic, Intuitive understanding -- WHAT symmetries? • Challenge to microscopy – Why THESE symmetries, which nuclei, why in THESE nuclei? • Complementarity

19. Ab initio: GFMC, NCSM, CCM (nuclei, neutron droplets, nuclear matter) NN NNN 1-2% calculations of A = 6 – 12 nuclear energies are possible excited states with the same quantum numbers computed S. Pieper, ANL

20. Asymptotic Freedom (for theorists) Density Functional Theory

21. r Diffuse V (r) Normal potential New Features in Weakly Bound Nuclei Spatially extended wave functions V (r) Halo Nuclei Normal nuclear density 11Li Density (log) p-n core r n-skin 0 10 20 Radius (fm) New form of matter – low density, diffuse, spatially extended, nearly pure neutron matter Altered shell structure

22. Possible Changes in Structure for Skin Nuclei J. Dobaczewski and W. Nazarewicz 126 p1/2 f5/2 h9/2 3p i13/2 f5/2 p3/2 2f N=5 p1/2 h9/2 p3/2 f7/2 f7/2 1h 82 h11/2 d3/2 g7/2 3s h11/2 s1/2 N=4 d3/2 2d g7/2 s1/2 d5/2 d5/2 1g 50 g9/2 very diffuse surface neutron drip line no spin orbit exotic nuclei/ hypernuclei g9/2 around the valley of b-stability harmonic oscillator

23. SUPERHEAVIES

24. Sph. Deformed Classifying Structure -- The Symmetry Triangle of Collective Behavior Dynamical Symmetries, Phase Transitions, Critical Point Symmetries, Order and Chaos E(5) X(5) Landau Theory Complementarity of macroscopic and microscopic approaches. Why do certain nuclei exhibit specific symmetries and not others? Why these specific evolutionary trajectories? What unknown regularities appear along the Arc? What will happen far from stability?

25. Skins and Skin Modes n p Neutron “skins” near the neutron drip lineOuter regions of low density nearly pure neutron matter

26. Production and use of Exotic Isotopes High Energy Heavy Ion Driver Fragmentation Target and Ion Separator Fast Beam Experiments Intense Stable Ion Beam Exotic Ion Beam Exotic Ions Stopped Beam Experiments (Traps) Gas Stopping Reaccelerated Beam Experiments High Energy Proton Driver ISOL Target/Ion Extraction Second Accelerator Intense Proton Beam Exotic Ion Beam Exotic Ions

28. Radioactive Ion Beam Facilities Timeline ISOLDE 2000 2005 2010 2015 2020 NSCL HRIBF CARIBU@ATLAS In Flight ISOL Fission+Gas Stopping Beam on target ISAC-II ISAC-I SPIRAL2 SPIRAL FAIR SIS RIBF RARF RIF

29. Exotic Nuclei Paradigm-Changing Discovery Potential Complexity – Simplicity Comprehensive Understanding of Atomic Nuclei Links to nano-science, high energy physics, and the cosmos Applications

30. Jargon  • Key to conference is communication • Biggest bottleneck to communication is jargon. • Examples (some may shock you): • Jlab: Partons, generalized parton distributions, the sea, quantitative relation of Q2 to size, Bjorken x… • RIA: island of inversion, yrast states, gamma vibrations, intruder states, K quantum number, B(E2) values, density functional theory…

31. Thanks to many from whom I have stolen slides, especially WitekHave a great Workshop !!!