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 Hartley Ӝ. #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 , 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 13 th September 2012

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

Background and motivation - Recent Calculations by Dudek (THEORETICIAN) Tetrahedral shape characterized by an α 32 in the expansion of the nuclear surface: 13 th September 2012

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

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

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 13 th September 2012 Odd spin- Tetra Candidate Masri et al., de Boer et al., Emling et al., Riley et al., Caprio et al. and Morrison et al.

Experimental Details  Analyzed data acquired using GAMMASPHERE (ANL, USA)  Produced by 148 Nd( 12 C,4n) 156 Dy reaction; 65MeV – Fusion Evaporation Reaction  2.5 x 10 9 events 13 th September 2012

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

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

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

Discussion - Systematic Comparison 13 th September 2012

Discussion - Systematic Comparison 13 th September 2012

Discussion - Band mixing Model 6 th September 2011 Spin

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

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

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 13 th September 2012

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

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

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