IN A SEARCH FOR TETRAHEDRAL SYMMETRIES IN 156Dy

1. IN A SEARCH FOR TETRAHEDRAL SYMMETRIES IN 156Dy S.N.T Majola†$, J F Sharpey-Schafer#*, R A Bark$, P Datta$, S P Bvumbi#, E A Georgieva Lawrie$, P Jones$, S M Mullins$,T Dinoko$#, D Negi$, L P Masiteng$, P Papka$‡, S Ntshangase†, O Shirinda$, Lee Riedinger and D. J HartleyӜ. #University of Western Cape, Department of Physics, P/B X17, Bellville, ZA-7535 RSA * University of Zululand, Department of Physics, P/B X1001, Kwa Dlangezwa, ZA-3886 RSA $ IThemba Laboratory for Accelerator Based Sciences, PO Box 722, Somerset, ZA-7129 RSA Ӝ University of Tennessee, Department of Physics, Knoxville, TN 37996-1200, USA § Faculty of Physics, St. Kliment Ohridski University of Sofia, Sofia 1164, Bulgaria. † University of Cape Town, Department of Physics, Private Bag X3,Rondebosch,7701, RSA ‡ University of Stellenbosch, Department of Physics, Private Bag X1, Maitland, 7601 X3, RSA 13th September 2012

2. Charts of The Nuclides - 156Dy is Localized in the transitional rare earth region - Has been studied extensively, especially at high spin - still poorly understood at low spin 156Dy Z=66 N=90

3. Background and motivation-Recent Calculations by Dudek (THEORETICIAN) Tetrahedral shape characterized by an α32 in the expansion of the nuclear surface: 13th September 2012

4. Background and Motivation -160 mass region Tetrahedral Minima Dudek Calculations for 156Dy (N=90) 13th September 2012

5. Background and Motivation- Possible Candidate for Tetrahedral in 156Dy Odd spin- Tetra Candidate Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al. 13th September 2012

6. Background and Motivation-Previous studies • Negative parity sequence previously known as an octupole bands • Absence results from a much greater E1 rate to the ground band • The purpose of this study is learn which of these explanations is correct Odd spin- Tetra Candidate Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al. 13th September 2012

7. Experimental Details • Analyzed data acquired using GAMMASPHERE (ANL, USA) • Produced by 148Nd(12C,4n)156Dy reaction; 65MeV – Fusion Evaporation Reaction • 2.5 x 109 events 13th September 2012

8. Experimental Details -GAMMASPHERE Sphere at Argonne National Laboratory 13th September 2012

9. Status of The Analysis (156Dy)- E2s 148Nd (12C, 4n) 156Dy Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al. Ground State Band Tetrahedral candidate Tetrahedral candidate 12th September 2012

10. Status of The Analysis (156Dy)- E2s Tetrahedral candidate Ground State Band (5- → 3-) still missing! 13th September 2012

11. Discussion-Systematic Comparison 13th September 2012

12. Discussion -Systematic Comparison 13th September 2012

13. Discussion- Band mixing Model 0 10 20 Spin 6th September 2011

14. Conclusion β-band (2+ → 0+) missing! 13th September 2012

15. Status of The Analysis (156Dy) (-ve parity bands) Tetrahedral candidate Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al. Ground State Band BandX 13th September 2012

16. Status of The Analysis (156Dy) (+ve parity bands) Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al. Ground State Band β-band 13th September 2012

17. Status of The Analysis (156Dy)(Gamma Band bands extended) 124Sn (36S, 4n) 156Dy Odd Gamma Band Odd Gamma Band 148Nd (12C, 4n) 156Dy Odd Gamma Band Even Gamma Band Odd Gamma Band Odd Gamma Band S-Band GS-Band 13th September 2012

18. Status of The Analysis (156Dy)(Gamma Band bands) 124Sn (36S, 4n) 156Dy Odd Gamma Band Odd Gamma Band 148Nd (12C, 4n) 156Dy Even Gamma Band Odd Gamma Band S-Band GS-Band 13th September 2012

19. Status of The Analysis (156Dy)(Spin and parity - Unknown) Ground State Band β-band 13th September 2012