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Theoretical Perspective Witold Nazarewicz (Tennessee) The Future of Gamma-Ray Spectroscopy

Theoretical Perspective Witold Nazarewicz (Tennessee) The Future of Gamma-Ray Spectroscopy August 17-18, 2007, FSU, Tallahassee, Florida. Introduction Historical perspective Getting there: transformation period Tomorrow (LRP): science motivators Summary. Historical Perspective.

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Theoretical Perspective Witold Nazarewicz (Tennessee) The Future of Gamma-Ray Spectroscopy

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  1. Theoretical Perspective Witold Nazarewicz (Tennessee) The Future of Gamma-Ray Spectroscopy August 17-18, 2007, FSU, Tallahassee, Florida Introduction Historical perspective Getting there: transformation period Tomorrow (LRP): science motivators Summary

  2. Historical Perspective • For theory highlights, see excellent review by Satula and Wyss: Rep. Prog. Phys. 68, 131 (2005) • Technological milestones not included • Early History: The Beginnings • 1900: Discovery of gamma rays by Villard • 1910: Bragg shows that gammas are rays • 1914: Rutherford and Andrade measure wavelengths (crystal diffraction). • Rutherford coins the name ‘gamma rays’ • 1924: Pauli suggests that hyperfine splitting is related to deformed nuclei • 1935: Schüler and Schmidt measure nuclear quadrupole moment (Casimir 1936) • 1936: Bohr’s paper on the deformed nuclear liquid drop. Vibrations. • 1937: Bohr and Kalckar. Rotations and the moment of inertia • 1938: Teller and Wheeler. Rotations. • 1939: Fission and shape degrees of freedom (Meitner & Frisch, Bohr & Wheeler)

  3. Age of Discovery • 1948: Nuclear shell model (Jensen and Goeppert-Mayer) • 1950: Deformed shell model (Rainwater) • 1951: Particle+rotor model; intrinsic system (A. Bohr) • 1952: Nuclear Jahn-Teller effect (particle-vibration coupling) • Rotational states in the actinides • 1953: Unified model (Bohr & Mottelson, Hill & Wheeler) • Coulomb excitation • 1954: Cranking model • 1955: Nilsson model (Nilsson and Moszkowski) • Intensity (Alaga) rules • 1958: Shell-model description of nuclear rotation: Elliott’s SU(3) model. Band termination • Nuclear superconductivity (Bohr-Mottelson-Pines, Belyaev) • 1960: Coriolis anti-pairing • 1961: Systematic calculations of moments of inertia (with pairing) • 1962: Discovery of fission isomers • 1963: Observation of 10+ state with alpha beam • 1964: Shell energy • 1965: Observation of 20+ state with heavy-ion beam • 1967: Theory of shell correction; prediction of superdeformation

  4. Vocabulary, Learning the Rules of the Game • 1969: “Nuclear Structure vol. I” by B&M • Superheavy magic numbers • 1970: First cranked HFB calculations • 1971: Backbending observed • 1972: Rotational alignment • 1974: Rotating liquid drop model • Interacting Boson Model introduced • Yrast traps (high-K isomers) found • 1975: Signature quantum number • “Nuclear Structure vol. II” by B&M • 1976: Rotating shell correction approach. Prediction of high-spin superdeformation • 1979: Cranked Shell Model. Angular momentum alignment. Quasiparticle diagrams • 1981: Prediction of uniform rotation around non-principal axis • 1983: Terminating bands predicted in heavy nuclei (observed 1984) • Discovery of a nuclear reflection-asymmetric rotor • 1984: Theory of reflection-asymmetric nuclear rotors • Discovery of the scissors mode • 1985: Rotational quasi-continuum studied • 1986: Discovery of high-spin superdeformation • Rotational damping predicted • 1988: Deep inelastic spectroscopy introduced • 1990: Discovery of identical bands • 1991: Discovery of magnetic rotation • First g.s. g-factor measurement in light neutron-rich nuclei using fast beams • 1993: Shears mechanism and explanation of magnetic rotation. Realization that • deformations can be associated with currents. • 1995: Gammasphere construction completed • Fundamentals of shell model tested • Basic collective modes characterized • Unified model extremely successful • Simple geometric and algebraic schemes introduced • Useful labels to characterize states and phenomena • Powerful phenomenology developed • Can interpret basic features of nuclear response to high spin • Tools of trade mastered • Data systematized • but… • Only qualitative understanding (e.g., MOI) • Lacking microscopic understanding rooted in interaction • …Labeling is not equivalent to understanding…

  5. Modern Era • 1995: Relativistic Coulex of light neutron-rich nuclei • 1996: Extreme s.p. SM picture of high-spin superdeformations • 1998: Prompt proton decay of a well-deformed rotational band • 1999: High-spin states of the heaviest elements • 2001: Rotating proton emitters • 2002: Superdeformed wobblers • Deep-inelastic studies of neutron-rich nuclei (-decays with prompt gammas) • Coulex with heavy neutron-rich ISOL beams • Important SD-yrast link in 152Dy found • First g-factor measurement on isomers in heavy neutron-rich nuclei with fast beams • 2003: Shell structure with two-proton knockout (gammas with knockout residues) • 2005: First nuclear moment measurement with radioactive beams by the recoil-in- • vacuum technique • Pygmy and GDR around 132Sn • Multiple Coulex with heavy proton-rich ISOL beams • Transfer in inverse kinematics with ISOL beams using -particle • coincidences and particle- angular correlations • 2006: Discrete states in 58Ni at E=42 MeV, E~4.4 MeV • Gamma ray spectroscopy used as a powerful tool • Life at the limits is demanding: many triggers required • Coupling of angular momentum with isospin extremely successful • Addressing basic questions of the nuclear many-body problem • Probing unique features of the polarized system • Contributions across disciplines • Applications? • From Quantity to Quality

  6. Extreme single-particle motion in superdeformed high-spin states R.W. Laird et al., Phys.Rev.Lett. 88, 152501 (2002) • Geometry of s.p. orbits the main factor • Weak dependence on interaction • Conclusion: selective data are needed! Unpaired HF and RMF W. Satula et al., Phys.Rev.Lett.77, 5182 (1996)

  7. distance excitation energy angular momentum (j-polarization) mass and charge N/Z ratio (isospin polarization) (e.g., the local central force) • also: • tensor force • two-body spin-orbit • second-order spin-orbit…

  8. SD SHE NN force nuclear magnetism What the @$#? pairing pygmy Why do we need GRETA? What physics will mainly benefit from unsurpassed n and tracking? Is this physics compelling enough? Questions

  9. Questions (1): Physics of Nuclei and Nuclear Astrophysics(NSAC Tribble Report) • What binds protons and neutrons into stable nuclei and rare isotopes? • What is the origin of simple patterns in complex nuclei? • When and how did the elements from iron to uranium originate? • What causes stars to explode?

  10. Questions (2): RIA Brochure

  11. S1n Brown & Sherrill, MSU

  12. Shell Model Density Functional Theory N+Z N-Z angular momentum temperature What are the missing pieces?

  13. Old paradigms, universal ideas, are not correct First experimental indications demonstrate significant changes No shell closure for N=8 and 20 for drip-line nuclei; new shells at 14, 16, 32… Near the drip lines nuclear structure may be dramatically different.

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

  15. EXAMPLES ARE USEFUL…

  16. Towards the Universal Nuclear Energy Density Functional Walter Kohn: Nobel Prize in Chemistry in 1998 isoscalar (T=0) density isovector (T=1) density isoscalar spin density Local densities and currents + pairing… isovector spin density current density Construction of the functional: E. Perlinska et al. Phys. Rev. C 69, 014316 (2004) spin-current tensor density kinetic density kinetic spin density Example: Skyrme Functional Total ground-state HF energy

  17. Nuclear DFT From Qualitative to Quantitative! S. Cwiok, P.H. Heenen, W. Nazarewicz Nature, 433, 705 (2005) • Deformed Mass Table in one day! • HFB mass formula: m~700keV • Good agreement for mass differences UNEDF (SCIDAC-2) will address this question!

  18. J. Dobaczewski and J. Dudek, Phys. Rev. C52, 1827 (1995) M. Bender et al., Phys. Rev. C65, 054322 (2002). Can be adjusted to the Landau parameters Data: high-spin SD states and GT decays very poorly determined • Important for all I>0 states (including low-spin states in odd-A and odd-odd nuclei) • Impact beta decay • Influence mass filters (including odd-even mass difference) • Limited experimental data available

  19. S2n S2p Brown & Sherrill, MSU

  20. sdfp-shell nuclei: SM-DFT interface E. Caurier et al., Phys. Rev. Lett. 75, 2466 (1995) 48Cr

  21. Intruder states in the sdpf nuclei intruder states G. Stoitcheva et al., Phys. Rev. C73, 061304(R) (2006) deformed structures 28 f7/2 20 d3/2 45Sc P. Bednarczyk et al., Acta Phys. Pol. B32, 747 (2001)

  22. Zdunczuk, Satula, Wyss, Phys.Rev. C71 (2005) 024305 • Excellent examples of single-particle configurations • Weak configuration mixing • Spin polarization! • Experimental data available

  23. spdf space 1p-1h cross-shell

  24. SM SM’ 0.4 SM’’ 0.2 ESM-EEXP (MeV) 0 -0.2 -0.4 44Sc 46Ti 47V 42Ca 42Sc 44Ti 40Ca 43Sc 45Sc 45Ti 44Ca 46V Pandya transformation on the cross shell ME Bansal, French, Phys. Lett. 11, 145 (1964); Zamick, Phys. lett. 19, 580 (1965) the isospin-dependent contribution to the excitation energy of a 1p-1h state sd fp sd fp Crucial for the island of inversion around 32Mg!

  25. 3.0 2.5 2.0 1.5 1.0 0.5 0 Coming attractions: dynamics of band termination! Satula, Stoitseva, et al. EXP SM SkO E(Imax)-E(Imax-2) [MeV] SLy4 42Ca 44Sc 44Ti 46Ti 42Sc 47V 44Ca 43Sc 45Sc 45Ti 46V

  26. SkO 0.15 Brandolini et al., PRC66, 021302 (2002) 0.10 6.5 SLy4 0.05 dEC=DEHF - DEHF [MeV] 0 (C) 6.0 -0.05 42Ca 43Sc 45Sc 46Ti 44Ti 40Ca 5.5 44Ca 44Sc 45Ti 47V 46V 42Sc 5.0 50Cr SkO SLy4 4.5 DE([f7/2]n) [MeV] SkO 46Ti off off on on SLy4 off on COULOMB SHIFT (W. Satula et. al) Relative Coulomb shift Coulomb: off on polarization of strong field Absolute Coulomb shift of terminating state ~500keV deformed g.s and spherical Imax Coulomb:

  27. Coupling of nuclear structure and reactions Nucleus is an open system ! Thomas/Ehrman shift • ab-initio description • continuum shell model • Real-energy CSM (Hilbert space formalism) • Gamow Shell Model (Rigged Hilbert space) • cluster models • Coupling between • electromagnetic and • particle decays

  28. Spectroscopy of open systems: proton emitters • Non-adiabatic theory: • B.Barmore et al., Phys.Rev. C62, 054315 (2000) • A.T. Kruppa and WN, Phys. Rev. C69, 054311 (2004)

  29. Equation of state, nuclear density functional, and heavy nuclei

  30. Microscopic LDM and Droplet Model Coefficients: PRC 73, 014309 (2006)

  31. Collective potential V(q) Universal nuclear energy density functional is yet to be developed Surface symmetry energy crucial Different deformabilities!

  32. P.H. Heenen et al., Phys. Rev. C57, 1719 (1998) • Shell effects in metastable minima seem to be under control. • Important data needed to fix • the deformability of the NEDF: • absolute energies of SD states • absolute energies of HD states • Advantages: • large elongations • weak mixing with ND structures

  33. Collective modes at extreme isospins

  34. LAND-FRS N-rich nuclei: Collective or single-particle? Skin effect? Threshold effect? Energy differential electromagnetic dissociation cross section Deduced photo-neutron cross section.

  35. T. Nakatsukasa et al., Nucl. Phys. A573, 333 (1994) spin-flip Z-rich nuclei: Collective M1 strength Enhanced in deformed N=Z nuclei Probes T=1 physics (g9/2)2 excitation

  36. E. Padilla-Rodal et al., Phys Rev. Lett. 94, 122501 (2005) A.Gorgen et al., Acta Phys.Pol. B36, 1281 (2005) COULEX with N-rich and Z-rich RIBs HRIBF p-rich multiple Coulex n-rich Coulex SPIRAL

  37. Conclusions

  38. Brown & Sherrill, MSU

  39. Science stuff • Making more isotopes is better than making fewer isotopes, but what’s the science driver behind N versus N+M isotopes? How many is enough? cases? OMB’s Midcourse Pep Talk: 3/12/2006, NRC RISAC, Joel Parriott, OMB It is always better to be selective Main emphasis on quality and relevance (hence longer experiments, programs)

  40. Summary THE END • Gamma ray spectroscopy is a mature tool. We learned the rules of the game. • Therefore, we can exploit them to our advantage when fighting for a weak signal. • The future lies in the spin-isospin direction: probing extreme spin and isospin polarization. Searching for the missing links in our understanding. • Program highly relevant to the microscopic many-body problem • Program highly relevant to the unification of nuclear structure and reactions Illustrative examples (my shopping list) • Probing the spin-isospin sector of the effective interaction • Unique laboratory: high-seniority states • Shell structure in n-rich nuclei and the tensor force • Coulomb interaction • Nucleus as an open quantum many-body system • Gamma and particle spectroscopy • Coupling to continuum (open channels) • The limit of mass and charge • Surface symmetry term and deformability: SD and HD • Non-perturbative Coulomb • Collective modes at large/small isospin • Skin modes • Magnetic excitations

  41. Philip Bredesen, Governor of Tennessee, PAC05 welcome address We are doing an inadequate job of explaining “outside” of our community why what we do is important “People who truly understand something, who truly have command of a subject, can explain it at some level to anyone who asks and is willing to try to understand an answer. The point is that if you were asked about something and had to resort to that's all very complicated and until you take a course in differential equations and then give me a blackboard I can't possibly make you understand, that that was more often a signal of a failure of the physicist to have a real command of the issue than of the failure of the person asking the question. I have adapted it to my own life is the "Wal-Mart Test." When I propose to take some course of action in the public sector, I do a thought experiment and imagine how I will explain it to the Wal-Mart checkout person. Let me clear that I don't mean in any way dumbing-down the idea, I mean taking the principle that if I understand well enough what I am doing, I can cogently explain it to another human being with a different reference point. If I can successfully do this thought experiment, I have the makings of a plan.”

  42. Philip Bredesen, Governor of Tennessee, PAC05 welcome address Big science has had a great run for the last 60 years: Manhattan project, Sputnik and space exploration, the explosion and excitement of particle physics and accelerator; the rationale was obvious and easy. But those rationales are getting long in the tooth now, and need to be reinvigorated. (...) the reality is that resources are scarce, the reality is that big science needs resources that only the government can supply, and the reality is that those scarce resources will go to those things that ordinary citizens think are important to themselves and to their children and to our nation. That's our job, to remake that connection in the 21st century. There's nothing wrong or demeaning in this; even Michelangelo had patrons who had a seat at the table and needed to be satisfied.

  43. 132Sn 130Sn 140Sn IS IV J. Terasaki, J. Engel, nucl-th//0603021 SKM*+QRPA+HFB

  44. (3He,p) N=Z line Measure the np transfer cross section to T=1 and T=0 states Both absolute s(T=0) and s(T=1) and relative s(T=0) / s(T=1) tell us about the character and strength of the correlations

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