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Structure and astrophysics from nuclear reactions
with exotic nuclei

Structure and astrophysics from nuclear reactions
with exotic nuclei July 14, 2009, University of the West of Scotland (Paisley Campus). Questions that drive the field: How to unify structure and reaction aspects of nuclei?

williamjevans
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Structure and astrophysics from nuclear reactions
with exotic nuclei

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  1. Structure and astrophysics from nuclear reactions
with exotic nuclei July 14, 2009, University of the West of Scotland (Paisley Campus) • Questions that drive the field: • How to unify structure and reaction aspects of nuclei? • How to incorporate open-channels effects into microscopic nuclear structure models? • How to incorporate microscopic structure information into reaction models? • What is the reliability of nuclear structure/astrophysics data extracted in a model dependent way from reaction measurements? How can we minimize the “model” aspect? • What is the preferred strategy for developing the microscopic reaction theory? Can large computers help? • Crucial Questions: • What is the essential input for developing the “universal” optical model potential? • How to take consistently into account breakup and transfer channels? Do we need more data at this point? • How far can surrogate reactions take us? Is (d,p) going to inform us about (n,g)? • How are cluster configurations born in nuclei? What is the microscopic foundation of the Ikeda diagram? • What is the interplay between continuum and isospin-breaking effects? • Can threshold effects be used as spectroscopic tools?

  2. Prog. Part. Nucl. Phys. 59, 432 (2007)

  3. (7.27) (14.44) (19.17) (28.48) (7.16) (11.89) (21.21) (14.05) (4.73) Excitation energy (13.93) (9.32) 11Li Mass number

  4. Physics of rare isotopes Interactions Many-body Correlations Open Channels • Interactions • Isovector (N-Z) effects • Poorly-known components come into play • Long isotopic chains crucial • Configuration interaction • Mean-field concept often questionable • Asymmetry of proton and neutron Fermi surfaces gives rise to new couplings (Intruders and the islands of inversion) • New collective modes; polarization effects • Open channels • Nuclei are open quantum systems • Exotic nuclei have low-energy decay thresholds • Coupling to the continuum important • Virtual scattering • Unbound states • Impact on in-medium Interactions

  5. Hagen et al, ORNL/UTK Ab initio: Reactions Nollett et al, ANL Coupled Clusters n+ CC GFMC Quaglioni & Navratil, LLNL 2008 No Core Shell Model + Resonating Group Method Overlap functions provide the link!

  6. n-10Be phase shifts with CD-Bonn NN interaction 10Be n 11Be: Quaglioni and Navratil, Phys. Rev. C 79, 044606 (2009) n-10Be phase shifts • NCSM/RGM calculation: • CD-Bonn 2000 NN potential • two-body effective interaction Nmax=7 @ h= 13 MeV • 10Be states: • n-10Be wave function extends to large distances • Relative kinetic energies decrease • Dramatic increase of 11Be binding energy 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 E [MeV] • Inversion between andstates reproduced 1/2- 1/2+ Expt. NCSM/RGM NCSM The proper description of extended n-10Be configurations leads to parity-inverted 11Be g.s.

  7. Reactions Workflow UNEDF Reaction Work Ground state Excited states Continuum states Target A = (N,Z) Structure ModelsMethods: HF, DFT, RPA, CI, CC, … Transition Density [Nobre] KEY: UNEDF Ab-initio Input User Inputs/Outputs Exchanged Data Related research UNEDF: VNN, VNNN… Transition Densities Veff for scattering Folding [Escher, Nobre] Eprojectile Transition Potentials Deliverables Coupled Channels or DWBA[Thompson, Summers] Hauser- Feshbach decay chains [Ormand] Partial Fusion Theory [Thompson] Residues (N’,Z’) Inelastic production Compound emission Two-step Optical Potential Elastic S-matrix elements or Resonance Averaging [Arbanas] Neutron escape [Summers, Thompson] Preequilibrium emission Voptical Global optical potentials Optical Potential [Arbanas]

  8. HRIBF experiments to understand the 26Al(p,g)27Si stellar reaction rate • Large amounts of 26Al have been observed in the Galaxy by g-ray telescopes. • The nucleosynthesis must be ongoing since the half-life is much shorter than the age of the Galaxy. • Source of 26Al is unknown. Most probable source is supernovae but novae also contribute. COMPTEL Studied mirror levels with 26Al(d,p)27Al First measurement of the 26Al(p,p)26Al excitation function

  9. Conclusions • Much excitement in the air • Low-energy reactions are difficult • Low-energy reactions with exotic nuclei are very difficult (low-lying thresholds) • Developing microscopic optical model is a key challenge • Exciting theoretical developments • Complex-energy shell model and SMEC provide unification, predict new phenomena, and will soon provide quantitative guidance • CDCC becomes more sophisticated (3-body continuum incorporated) • Other approaches, e.g., ADWA, very useful • Ab-initio approaches • Time-dependent approaches • Spectroscopic factors have been overrated. The overlap amplitude provides a link between structure and reactions. • What astrophysical reactions are crucial? Need for sensitivity studies. • Unique, and sometimes spectacular, data from RNB facilities provide important insights, but… • More quality theory needed • Exclusive data important to calibrate models, but… • More selectivity is needed

  10. Thank you!

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