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Nuclear Structure'06: Questions and Challenges Witold Nazarewicz (Tennessee)

Nuclear Structure'06: Questions and Challenges Witold Nazarewicz (Tennessee) "The Expanding Physics of Jefferson Lab" June 12-14, 2006 Jefferson Lab, Newport News, VA. Introduction Challenges and questions Relevance to CEBAF@JLab Recent examples A comment on RIA Summary. Distance.

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Nuclear Structure'06: Questions and Challenges Witold Nazarewicz (Tennessee)

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  1. Nuclear Structure'06: Questions and Challenges Witold Nazarewicz (Tennessee) "The Expanding Physics of Jefferson Lab" June 12-14, 2006 Jefferson Lab, Newport News, VA • Introduction • Challenges and questions • Relevance to CEBAF@JLab • Recent examples • A comment on RIA • Summary

  2. 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

  3. Energy-dependent resolution (use different microscopes to probe different degrees of freedom) pion p+ ~140 MeV QCD scale 1000 MeV g g g g g g g g g g g deuteron ~3 MeV N-binding scale pion-mass scale _ _ _ _ _ _ _ _ _ d d d d d d d d d d d 10 MeV 100 MeV u u u u u u u u u u u u d collective ~1 MeV J. Dobaczewski, RIA Summer School, 2004

  4. How do protons and neutrons make stable nuclei and rare isotopes? What is the origin of simple patterns in complex nuclei? What is the equation of state of matter made of nucleons? What are the heaviest nuclei that can exist? When and how did the elements from iron to uranium originate? How do stars explode? What is the nature of neutron star matter? How can our knowledge of nuclei and our ability to produce them benefit the humankind? Life Sciences, Material Sciences, Nuclear Energy, Security ✔ • What is the QCD basis for the inter-nucleon force? • What are the limits of our understanding of nuclear structure? • What is the impact of short distances on low-momentum physics? • At what distance and energy scale does the underlying quark and gluon structure of nuclear matter become evident? • How do hadrons change in nuclear medium? • What can the introduction of an “impurity” (in the form of a ) tell us about the nuclear environment and the N-N force? ✔ ✔ Questions that Drive the Field(as in the RIA Brochure) ✔ Physics of nuclei ✔ Nuclear astrophysics ✔ Applications of nuclei Electron scattering provides an ideal microscope for nuclear structure physics

  5. Nuclear Structure Theory Overarching goal: • This is a lofty and ambitious goal that has been a “Holy Grail” 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 • Violates the criteria of perfect theory as defined by Gross: • No infinities • No new physics at short distances/high energies • No adjustable parameters • But… Very few theories that explain reality are perfect… 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

  6. Effective Field Theory tells us that: • Short-range (high-k) physics can be integrated out (no need to worry about explicit inclusion of hard core when dealing with low-k phenomena) • Successive two-body scatterings with short-lived high-energy intermediate states unresolved → must be absorbed into three-body force • Power counting can be controlled • … but the operators have to be renormalized (i.e., consistent with the power counting) Weinberg’s Third Law of Progress in Theoretical Physics: “You may use any degrees of freedom you like to describe a physical system, but if you use the wrong ones, you’ll be sorry!” D. Furnstahl, INT Fall’05

  7. Nuclear Structure: the interaction Effective-field theory (χPT) potentials Vlow-k: can it describe low-energy observables? • Quality two- and three-nucleon interactions exist • Not uniquely defined (local, nonlocal) • Soft and hard-core • The challenge is: • to understand their origin • to understand how to use them in nuclei Bogner, Kuo, Schwenk, Phys. Rep. 386, 1 (2003) N3LO: Entem et al., PRC68, 041001 (2003) Epelbaum, Meissner, et al.

  8. Ab initio Configuration interaction Density Functional Theory Bottom-up approaches to nuclear structure Roadmap Collective and Algebraic Models (top-down) Theoretical approaches overlap and need to be bridged

  9. Ab initio: GFMC, NCSM, CCM (nuclei, neutron droplets, nuclear matter) S. Pieper, ENAM’04 1-2% calculations of A = 6 – 12 nuclear energies are possible excited states with the same quantum numbers computed

  10. Ab Initio Nuclear Structure Theory (with bare NN+NNN interactions) • Quantum Monte Carlo (GFMC) 12C • No-Core Shell Model 13C • Coupled-Cluster Techniques 16O • Unitary Model Operator Approach • Faddeev-Yakubovsky • Bloch-Horowitz • … The nucleon-based description works to <0.5 fm • Input: • Excellent forces based on the phase shift analysis • EFT based nonlocal chiral NN and NNN potentials • Challenges: • Interaction: NNN • How important is NNNN? See nucl-th/0606017for 4He estimates • How to extend calculations to heavier systems? • Treatment of weakly-bound and unbound states, and cluster correlations

  11. Experiment in red 6He and 11Li Charge Radii measured by laser spectroscopy ANL: 6He TRIUMF: 11Li DCM SVMC FMD Inert core GFMC NSCM L-B Wang et al., Phys. Rev. Lett. 93, 142501 (2004) Sanchez et al., Phys. Rev. Lett. 96, 033002 (2006)

  12. Diagonalization Shell Model (medium-mass nuclei reached;dimensions 109!) Honma, Otsuka et al., PRC69, 034335 (2004) and ENAM’04 N=0 CI works great, but… 1024 is not an option!!! Smarter solutions are needed Martinez-Pinedo ENAM’04 Challenges: Configuration space Effective Interactions Open channels

  13. Nuclear DFT (non-relativistic and relativistic) From Qualitative to Quantitative! • Deformed Mass Table in one day! • HFB mass formula: m~700keV • Good agreement for mass differences

  14. Old paradigms, universal ideas, are not correct Near the drip lines nuclear structure may be dramatically different. Experimental indications from RNB facilities (ISOLDE, NSCL, RIKEN, SPIRAL,…) demonstrate significant changes No shell closure for N=8 and 20 for drip-line nuclei; new shells at 14, 16, 32…

  15. Why is the shell structure changing at extreme isospins? Interactions Many-body Correlations Open Channels • Interactions • Isovector (N-Z) effects • Poorly-known components of the effective interaction come into play (spin-orbit and tensor interactions and related fields)

  16. Shell Model Ab Initio Density Functional Theory Isospin dependence What are the missing pieces?

  17. T. Otsuka et al. Phys. Rev. Lett 87, 082502 (2001) SM, Gogny J. Dobaczewski, nucl-th/0604043 SO densities (strongly depend on shell filling) Skyrme-DFT Spin-Orbit and Tensor (among many possibilities)

  18. Why is the shell structure changing at extreme isospins? • Many-body correlations • Pairing • Deformation (islands of inversion) • Coexistence phenomena • Is the shell model (HF) picture valid in the limit of very strong • configuration interaction? • Dripline systems • Superheavies • Low-lying open channels • The nucleus is an open quantum system • Exotic nuclei unify structure and reaction aspects • Continuum coupling can influence bulk properties (such as binding and sizes) and spectroscopy (shell effects)

  19. Coupling of nuclear structure and reaction theory (microscopic treatment of open channels) • ab-initio description • continuum shell model • Real-energy CSM (Hilbert space formalism) • Gamow Shell Model (Rigged Hilbert space) • cluster models N. Michel et al., GSM nucl-th/0601055 J. Rotureau et al., DMRG nucl-th/0603021 Thomas/Ehrman shift • N. Michel et al., Phys. Rev. Lett. 89, • 042502 (2002); Phys. Rev. C67, 054311 (2003); Phys. Rev. C70, 064311 (2004) • G. Hagen et al, Phys. Rev. C71, 044314 (2005)

  20. Soon: implementation to hadron spectroscopy

  21. NSCL@MSU 2005 • How well does nuclear theory describe the energy and spatial structure of the single particle wave functions? • Can the parameterized N-N force adequately describe the short-range correlations among the nucleons? • Electron-induced proton knock-out • What is the role of long-range correlations and open channels?

  22. Do very long-lived superheavy nuclei exist? What are their physical and chemical properties? How to get there? HRIBF 2005 What are the limits of atoms and nuclei?

  23. lifetimes > 1y Superheavy Elements S. Cwiok, P.H. Heenen, W. Nazarewicz Nature, 433, 705 (2005)

  24. n n p p p n Skins and Skin Modes

  25. Collective or single-particle? Skin effect? Threshold effect? LAND-FRS Energy differential electromagnetic dissociation cross section Deduced photo-neutron cross section.

  26. Towards the Nuclear Energy Density Functional (Equation of State) • EXPERIMENT: • Giant resonances (especially GMR) • Neutron radii • PREX: 208Pb Neutron Distribution RMS Radius Experiment • Heavy ion collisions • But… nucleus is a very finite system! The region of nuclear surface is not a low-density nuclear matter (LDA is a poor approximation for nuclei) • Challenges: • density dependence of the symmetry energy • neutron radii • clustering at low densities

  27. Macroscopic Droplet Model Radii "From finite nuclei to the nuclear liquid drop: Leptodermous expansion based on self-consistent mean-field theory” P.-G. Reinhard, M. Bender, W. Nazarewicz, T. Vertse Phys. Rev. C 73 (2006) 014309 residual shell effects 8000 1000 300 125 around 1fm

  28. 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

  29. Tests of the Standard Model Parity violation studies in francium 126 82 Weak interaction studies in N=Z nuclei EDM search in radium 50 protons • Specific nuclei offer new opportunities for precision tests of: • CP and P violation • Unitarity of the CKM matrix • … 82 28 20 50 8 28 neutrons 2 20 How will we turn experimental signals into precise information on physics beyond the standard model? 8 2

  30. - + - + - + + - + - energy Schiff moment: L 0 R octupole deformation 1/2- 55.2 keV 0 1/2+ experiment 225Ra

  31. RARE ISOTOPE ACCELERATOR EXOTIC BEAM FACILITY

  32. 3/12/2006, NRC RISAC, Dennis Kovar, DOE

  33. 3/12/2006, NRC RISAC, Dennis Kovar, DOE Exotic Beam Facility

  34. The Bottom Line (as the RIAUO EC understands it) • On February 15, 2006, Secretary of Energy Samuel Bodman, in testimony before the Science Committee of the House, stated that there were no immediate plans to move forward with RIA at the present time but that DOE was planning to have preliminary engineering design for an exotic beam facility in about 5 years. • Two points should be clearly understood. First, it is clear that a future exotic beam facility remains a priority for the US government. Second, this may represent only a 2-year delay in the start of a facility since prior to Secretary Bodman's statements it was likely that preliminary engineering design for RIA would have begun in 2009. • We are optimistic that the prospects for forefront exotic beam research with an advanced facility in the US remain bright and that recent statements from DOE are an encouraging step forward towards the realization of that goal.

  35. There is an on-going National Academy study of the science with exotic beams that will play an important role in vetting the current government plans. And there will be a new LRP process very soon that will also assess exotic beam science and the priorities of our field. Compelling and unique science is the key In what areas can we make a unique contribution of high scientific priority?

  36. The study of nuclei is a forefront area of science. It is this research that makes the connection between the Standard Model, QCD phenomena, many-body systems, and the cosmos. A comprehensive description of nuclei and their reactions is needed Nuclear structure and reactions are important not just for nuclei: Understanding the quantum many-body problem at various distance/energy scales Testing the fundamental laws of nature Understanding stellar evolution and how the elements were made Society (national security, energy, medicine…) Theory and experiment are both needed to achieve this goal THE END The Nucleus: an integral part of nuclear science We hope to put together the coherent picture of the nucleus Electron scattering on radioactive nuclei

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