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Nuclear Structure Now (precision and discovery)

Nuclear Structure Now (precision and discovery). C.J.(Kim) Lister Lister@anl.gov. Our Nuclear Domain. RIBF@RIKEN. FAIR@GSI. FRIB@MSU. A different view of our nuclear world. Ab-initio Greens Functional Monte Carlo Calculations. Pieper and Wiringa (ANL) Described in NP A751 516c (2005).

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Nuclear Structure Now (precision and discovery)

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  1. Nuclear Structure Now(precision and discovery) C.J.(Kim) ListerLister@anl.gov

  2. Our Nuclear Domain

  3. RIBF@RIKEN FAIR@GSI FRIB@MSU

  4. A different view of our nuclear world

  5. Ab-initio Greens Functional Monte Carlo Calculations Pieper and Wiringa (ANL) Described in NP A751 516c (2005)

  6. Neutron Stars

  7. Testing Ab-Initio Calculations

  8. 6He RMS Radii of 6,8He P.Mueller et. al (ANL)

  9. RMS Radii of 6,8He After some convergence issues were resolved, predictions of charge radii very good, ~ 1%…..matter radii not quite so good. L.-B. Wang et al., PRL 93, 142501 (2004) P. Mueller et al., PRL 99, 252501 (2007).

  10. Transfer Reactions ANL-UWM CollaborationA. H. Wuosmaa et. al. PRL94 082592 and PRC72 061301(R) 2005 Example: 6He(d,p)7He Issues: How reliable are calculations of unbound states? Is there a low lying state below 1MeV? Data Fit to g.s. and Ex=2.25,G=3.0 MeV state Sn=0.533 l=1 p3/2 No renormalization to QMC calculations

  11. Transfer Reactions Compare: 6He(d,p)7He and 8Li(d,3He)7He Issues: Is spectroscopy of broad resonances possible? 1/2 - Yes!!Using selective in both population and decay channels 5/2-

  12. The Special Case of Beryllium Nuclei

  13. Key Issues: Microscopically, how do the neutrons really form a potential to bind the nucleus? Is it the same for all states?

  14. Investigating 8Be …..Here in Mumbai!! Upshot: Test of electromagnetic decay from unbound resonance Experiment Ab-Initio Theory

  15. The Bound States of 10Be 9Be+n 6812 6179 6263 2- 0+ 219 2895 1- 2811 E1 2+ 2589 M1/E2 5958 5960 E2 E1 2590 E1 2+ 3367 E2 0+ 10Be

  16. A=10 nuclei provide a sensitive test of GFMC Very sensitive to the effects of 3-body correlations. 10Be Data Compilation GFMC Theory Q ≤ 0 Q ≥ 0 S.C. Pieper, K. Varga and R.B. Wiringa, Phys. Rev. C 66, 044310 (2002).

  17. The Ab-Initio projection of T=0 and T=1 density Ken Nollett (ANL) and Brent Graner (UC) visulization of 10Be J=21 state (2008)

  18. The Traditional Shell Model (1956+++) Kurath, Cohen and Kurath, Millener and Kurath, Millener and Warburton R=11.3

  19. 10Be : A popular nucleus Ratio Calc. Author (e2fm4) (e2fm4) Okabe MO 11.26 0.44 25.6 Caurier NCSM 6.58 0.13 49.5 Itagaki TMO 11.8 0.70 16.9 Navratil NCSM 5.4 0.17 32.7 Arai MCM 4.8 0.10 48.0 Wiringa GFMC 7.89(30) 2.08(26) 3.8 EXPT 10.5(1.0) ?? ?? MO : Molecular orbit model, N. Itagaki and S. Okabe, Phys. Rev. C 61, 044306 (2000). NCSM : No-core shell model, E. Caurier et al., Phys. Rev. C 66, 024314 (2002). TMO : Triaxial Molecular Orbital, N. Itagaki et al., Phys. Rev. C 65, 044302 (2002). MCM : Microscopic cluster model, K. Arai, Phys. Rev. C 69, 014309 (2004). GFMC : Greens Functional Monte Carlo, R. Wiringa and S. Pierper et al., Private Communication.

  20. Previously measured DSAM J=21 lifetime in 10Be Evaluated t = 180(18) fs • Systematic problems of:- • Initial recoil velocity ill-defined • Stopping powers poorly known • Very slow recoils • State feeding poorly known • Detector angle poorly defined • At the time these measurements WERE cutting edge and provided discriminating tests of the (new) intermediate-coupling shell model (Kurath et al 1958) . • But now we need better! All DSAM measurements E.K. Warburton et al., Phys. Rev. 129, 2180 (1963). G.C. Morrison et al., - unpublished (1965). E.K. Warburton et al., Phys. Rev. 148, 1072 (1966). T.R. Fisher et al., Phys. Rev. 176, 1130 (1968).

  21. 11Li β-delayed 1-n emission Line shape depends on • Energies and intensities of all neutron branches feeding the level • Lifetime of the level • Angular correlation between gamma ray and neutron Y. Hirayama et. al. Phys Lets B611 239 (2005)…..polarized b-decay at ISAC/TRIUMF (high stats) F. Sarazin et al., Phys. Rev. C 70, 031302(R) (2004)….b-decay at ISAC / TRIUMF

  22. The Doppler Shift Attenuation Method (DSAM)

  23. The Doppler Shift Attenuation Method g Free Space Eg = Eo {1 + (v0/c)Cosq} q v0 g Stopping Eg = Eo {1 + F(t)Cosq} q 1 v(t) F(t) Actually, recoils are sufficiently swift (v/c ~6%) that 2nd order relativistic is correction needed 0 log(t)

  24. What SRIM shows us SLOW Ions…. 1 MeV 10Be in 100mg/cm2 Li on 6mg/cm2 Au FAST Ions…. 15 MeV 10Be in 100mg/cm2 Li on 6mg/cm2 Au (99.99% electronic stopping) J.F. Ziegler, J.P. Biersack and M.D. Ziegler http://www.srim.org

  25. 7Li(7Li,a)10Be at 10 MeV 10Be (g.s) = 18.2 MeV 10Be* (3.3) = 16.5 MeV 10Be* (5.9) = 15.0 MeV 10Be α DSAM* E.A. McCutchan et. al. (ANL) DSAM done properly:- 2-body kinematics High recoil velocity Well defined recoil direction Well defined gamma direction Control of state population

  26. Recoil-gamma time Recoil - g Gated Data 3 mg/cm2 Cu backing ΔE Etot in Ion Chamber A=10 q=3 selected with FMA

  27. 2 Counts Counts  Energy Energy But… • Need some finite thickness of production material • Need nuclei to recoil out of target N 1 3 2 Extracting the lifetime from mean  Ideally you want all decays in the stopping material 1 2 3 ’s weighted by # of decays at given time t time  determines weight time

  28. Results (1): First excited State with Jp=2+ at 3367 keV 7Li t = 290( )fs +200 -100 t = 270( )fs +100 -60 66mg/cm2 7Li on 6.95mg/cm2 Au • = 0.0525(5) t = 245(35)fs 115mg/cm2 7Li on 2.69mg/cm2 Au 7Li b = 0.0560(5) 7Li 288mg/cm2 7LiF2 on 2.48mg/cm2 Cu b = 0.0535(5)

  29. Traditional DSAM analysis……and GS alignment 100 mg/cm2 7Li on 2.33 mg/cm2 Au

  30. Results so far for 3369keV J=2 state

  31. The Bound States of 10Be 6179 6263 2- 0+ 219 2895 1- 2811 E1 2+ 2589 M1/E2 5958 5960 E2 E1 2590 E1 2+ 3367 E2 0+ 10Be 9Be+n 6812

  32. g g d d I2t2 I2t2 2+ 2+ Some Detective Work Required a b 1- I1t1 Is it possible to untangle the two-line Jp=1-,2+ mess? The states are only 1.8keV apart and have similar, short lifetimes

  33. What we have learned so far

  34. First J = 2+ state in 10Be NNDC transition strength was Our new transition strength Ab-initio transition strength Note: The predicted ab-initio summed E2 decay strength is:

  35. Second J = 2+ state in 10Be This work NNDC lifetime Sarazin et. al. Much smaller than GFMC which initially predicted 2.08(26) e2fm4 Theory seems to have much too much mixing of Jp=2+ states. The original GFMC with V18 and IL2 three body force predicted R=3.8

  36. Lessons Learned We set out to test a model that was thought to be good at the <10% level. Tests were for calc. stability & validating 3-body forces. We Found: Good agreement in absolute binding energy of the ground state. Modest agreement in the binding energies of the excited states (correct ordering, too close in energy) Good agreement in the total collectivity, without resorting to any effective charges. Modest agreement in the distribution of strength.

  37. Conclusions for 10Be In Experiment We have made a precise measurement of the lifetime of the first excited state in 10Be. Reliable <5% DSAM IS possible. We have determined the ratio R, which shows there is very little mixing between first and second J=2 states. In Theory We need to reconcile the differences: Does the experimental distribution of B(E2) strength allow us to constrain the models of 3-body forces? YES, but reveals more work is needed

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