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Search for chiral doublet structures in odd-A 79 Kr with the Hyperball2 array @ CYRIC

Search for chiral doublet structures in odd-A 79 Kr with the Hyperball2 array @ CYRIC. CYRIC/Tohoku University J.Timar ATOMKI (Hungary) K. Starosta (MSU) R. Wadsworth Univ. of York (U.K) G. Rainovski (SUNY at Stony Brook). 134 Pr. Chirality. A~130 Odd-Odd ( p h 11/2 n h 11/2 )

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Search for chiral doublet structures in odd-A 79 Kr with the Hyperball2 array @ CYRIC

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  1. Search for chiral doublet structures in odd-A 79Kr with the Hyperball2 array @ CYRIC CYRIC/Tohoku University J.Timar ATOMKI (Hungary) K. Starosta (MSU) R. Wadsworth Univ. of York (U.K) G. Rainovski (SUNY at Stony Brook)

  2. 134Pr Chirality

  3. A~130 Odd-Odd (ph11/2nh11/2) 132Cs,130Cs,128Cs,126Cs,124Cs 134La,132La,130La 134Pr,132Pr 136Pm 140Eu,138Eu Odd-A (p(h11/2)2nh11/2) 135Nd A~190 Odd-Odd (ph9/2ni13/2) 188Ir (D. L. Balabanski et. al.,Phys. Rev. C 70, 044305 (2004)) A~80 (unexplored) Odd-Odd (pg9/2ng9/2) 80Br(?), Odd-A (p(g9/2)2n(g9/2)) 79Kr(?) A~105 Odd-Odd (pg9/2nh11/2) 106Ag, 106Rh,104Rh,102Rh 100Tc (P.Joshi’s Talk), Odd-A (pg9/2n(h11/2)2) 105Rh, 103Rh

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

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

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

  7. 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

  8. 70Zn + 13C

  9. 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

  10. Excitation function measurement and preliminary experiment at Stony Brook • Excitation function measurements for two reactions at Van de Graaff Tandem/LINAC facility • Beam time scheduled in April (Timar Janos ATOMKI, Hungary & Stony Brook NATO grant) • One week in-beam g-g coincident measurement with better of the two reactions. (6 BGO suppressed Ge array) • Preliminary analysis

  11. In-beam experiment preparation • Hyperball2 frame/Rail (March assembly) • Target chamber (in the making) • BGO counters (April assembly) • Cryogenic system/LN2 transport (in progress) • Power issue • DAQ

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

  13. 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

  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. 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)

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

  17. 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

  18. 132Ce Rotation

  19. 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

  20. 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

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

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