CYRIC @Tohoku University Dept. of Physics, Tohoku University T.Fukuchi (Rikkyou University)

1. Search for chiral doublet structures in mass A~80 region: odd-A 79Kr and odd-odd 80Brwith the Hyperball2 array @ CYRIC CYRIC @Tohoku University Dept. of Physics, Tohoku University T.Fukuchi (Rikkyou University) N.Aoi (RIKEN) J.Timar ATOMKI (Hungary) K. Starosta (MSU) R. Wadsworth Univ. of York (U.K) G. Rainovski (SUNY at Stony Brook)

2. R jn intmd. short long jp Rh Isotpes Odd-A jn R intmd. short Odd-Odd jp long J. Timar et al. to be submitted.

3. A~130 Odd-Odd (ph11/2nh11/2-1) 132Cs,130Cs,128Cs,126Cs,124Cs 134La,132La,130La 134Pr,132Pr 136Pm 140Eu,138Eu Odd-A (p(h11/2)2nh11/2-1) 135Nd,135Ce A~190 Odd-Odd (ph9/2ni13/2) 188Ir Even-Even (ph11/2(d5/2,g7/2)n(h11/2)2) 136Nd A~80 (unexplored) Odd-Odd (pg9/2ng9/2-1) 80Br(?), Odd-A (p(g9/2)2ng9/2-1) 79Kr(?) A~105 Odd-Odd (pg9/2-1nh11/2) 106Ag, 106Rh,104Rh,102Rh 100Tc Odd-A (pg9/2-1n(h11/2)2) 107Ag,105Rh, 103Rh

4. Possible chiral structure in 79Kr 79 1~2.5% p(g9/2)2ng9/2 5~10% 50% G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)

5. Hyperball2 frame/Rail (March ) BGO counters (April ) Target chamber Cryogenic system/LN2 transport Installation of dets. Electronic set up DAQ Making of targets (A. Lipski) Excitation functions A gg coincidence run A Road to HB2 experiment at CYRIC

6. 70Zn(13C,xnypzag)

7. gg coincidence measurement with Stony Brook array (6 Compton suppressedGe dets.) 1154 827 559 1026 1144 1144 700 1026 827

9. Hyperball2 runJune 14~17, 2005 (11shifts) • Reaction: 70Zn(13C,4n)79Kr • Target: 1mg/cm2 self-supporting 70% 70Zn • Beam: 13C3+ @ 65MeV • 4 Clovers + 10 single Ge dets. participating in trigger (out of 12 mounted) • Trigger • Triple or higher Ge coincidence • Compton suppressed; Peak to total=~20% • Coincidence window 150ns

10. Hyperball2 array performance • Total peak photo efficiency: 0.025 @ 827 keV • Dead time (pile up, reset): 0.1 • Over Compton suppression: 0.3 • Dead time due to noise: 0.2 • FWHM (intrinsic) • ~4keV (single Ge) & ~3keV (Clover) • DAQ dead time: 0.3 827keV gated 1026 1144 827

11. Performance improvement • Number of detectors 14 →18 • Collimator for Ge detectors • Over suppression 0.3 → 0.01 Total photo peak efficiency = 0.025 X1.3X1.4 =0.045 @ ~827 keV For triple coincidence, performance improvement by 1.823 =6

12. Proposed experiment with the Hyperball2 array • 70Zn(13C,4n)79Kr @ 65MeV • Pb backed 1mg/cm270Zn target (ready) • Reduction of Doppler broadening • ~200K counts for 827keV peak X 6=1.2M • 1.2MX0.01=12K for the transitions of interests in 12 shifts with triple coincidence measurement • 3 shifts for 80Br test run with the same reaction but lower energy @55MeV Total of 15 shifts

13. 70Zn + 13C

14. Total cross section σ=~1b Beam intensity I: 2pnA Target thickness S: 1mg/cm2 Average number of gamma rays emitted:10 Rate estimate ~106 gamma/second

15. σ=~500mb Beam intensity I: 2pnA Target thickness S: 1mg/cm2 Average number of gamma rays emitted:10 Total photo peak efficiency of Hyperball2: 5% 79Kr yield estimate (79Kr: 54K particle/second)X10X(0.05)3X24x3600 ~6 million g-g-g coincidence in 79Kr per day 24million g-g-g coincidence in requested 12 shifts equivalent to 72 g-g unfolded event

16. Doublet bands in 10545Rh60 J. Timar et al., PLB598,178 (2004). Energy [MeV] Spin [ħ]

17. Doublet bands in odd-even 13560Nd75S. Zhu et al., PRL 91(2003) 132501. Energy [MeV] Spin [ħ]

18. Hyperball2experiment @ CYRIC (Being assembled) • 70Zn(13C,4n)79Kr @58MeV or 65Cu(18O,p3n)79Kr @65MeV • [ Single Ge (60%) +BGO ] x 14 + [ Clover type Ge (125%) +BGO ] x 6 → Photopeak efficiency ~ 5% at 1 MeV • UMEM/Double buffering

19. Possible chiral structure in 79Kr p(g9/2)2ng9/2 G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)

20. In-beam experiment with Hyperball2 • Advantages • Large total photo peak efficiency (g-g-g coincidence) • Transistor reset type (high counting rate→ high intensity beam) • BGO as a multiplicity filter (12x6+6x14=156 elements) • Clover detector as Compton polarimeter • Disadvantages • Few angles (detectors placed mostly around 90º) → lower angular correlation sensitivity

21. Ge det. status at glance • Eurisys Single Crystal Ge (r.e. ~60%) X 5 • Ortec Single Crystal Ge (r.e. ~60%) X 10 • Eurisys Clover type Ge X 6 • (r.e. ~20%, add-back 125%) Total X 21 Ready for use X 12 Being Repaired X 6 (G2,G3,G14,S/N1,S/N3,S/N4) Problematic X 3 (G1,G9,G1)

22. Target chamber for in-beam experiments with Hyperball2 at CYRIC

23. Important theme of nuclear structure studiesNuclear deformation • Spontaneous symmetry breaking • Collective degree of freedom • Nuclear Shape • Coupling of single particle degree and collective degree of freedom

24. 132Ce Rotation

25. Unique Parity Orbit N=5 • Simple Harmonic Oscill. • (SHO) • p=(-1)N N=4 • SHO+l•s • Major shell consisting of • majorities of normal parity • and unique parity orbitals. N=3 N=2 • The ph11/2nh11/2 confg. • is comprised of two • unique parity orbitals. N=1 0s 0s N=0 0s1/2 SHO SHO+l•s

26. R jp jn Possible realization for chiral geometry:odd-odd nuclei in the A~130 region intmd. • Z=~55 N=~75 • Triaxial mass distribution (shape). • Fermi level lies • low in proton h11/2subshell, • highin neutron h11/2subshell. • Collective rotation of triaxial rotor • with irrotational flow moment of inertia. short long

27. Chiral Geometry in Nuclei Mutually orthogonal coupling of three angular momenta in odd-odd nuclei K.Starosta Phys. Rev. Lett. 86, 971 (2001).

28. 134Pr Chirality