Search for chiral doublet structures Search for chiral doublet structures in odd-A in odd-A 7979Kr Kr
with the Hyperball2 array @ CYRICwith 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)
LR
LR
ROLLOR
LLRR
O
,||,||
,||,||
,0],[
HH
H
IMIM
IM
IMIM
IMIMH
iIM
IM
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LR
LR
134Pr
ChiralityChirality
A~130Odd-Odd (h11/2h11/2)132Cs,130Cs,128Cs,126Cs,124Cs134La,132La,130La134Pr,132Pr136Pm140Eu,138EuOdd-A ((h11/2)2h11/2)135Nd
A~105Odd-Odd (g9/2h11/2)106Ag,106Rh,104Rh,102Rh100Tc (P.Joshi’s Talk),Odd-A (g9/2h11/2)2)105Rh, 103Rh
A~190Odd-Odd (h9/2i13/2)188Ir (D. L. Balabanski et. al.,Phys. Rev. C 70, 044305 (2004))
A~80 (unexplored)Odd-Odd (g9/2g9/2)80Br(?),Odd-A (g9/2)2g9/2))79Kr(?)
Doublet bands in odd-even Doublet bands in odd-even 1351356060NdNd7575
S. Zhu et al., PRL 91(2003) 132501.S. Zhu et al., PRL 91(2003) 132501.
Spin [ħ]
En
erg
y [M
eV]
Doublet bands in Doublet bands in 1051054545RhRh6060
J. Timar et al., PLB598,178 (2004).J. Timar et al., PLB598,178 (2004).
4 8 12 16 20 240
2
4
6
8
Spin [ħ]
En
erg
y [M
eV]
Possible chiral structure in 79KrPossible chiral structure in 79Kr
G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)
(g9/2)2g9/2
Hyperball2Hyperball2 experiment @ CYRICexperiment @ 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
7070Zn + Zn + 1313CC
7979Kr yield estimateKr yield estimate
• 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: 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 shifts24million g-g-g coincidence in requested 12 shiftsequivalent to 72 g-g unfolded eventequivalent to 72 g-g unfolded event
Excitation function measurement and Excitation function measurement and preliminary experiment at Stony Brookpreliminary 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
In-beam experiment preparationIn-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
Possible chiral structure in 79KrPossible chiral structure in 79Kr
G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)
(g9/2)2g9/2
50%
5~10%
1~2.5%
In-beam experiment with Hyperball2In-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
Rate estimateRate estimate
• Total cross section σ=~1b• Beam intensity I : 2pnA• Target thickness S: 1mg/cm2
• Average number of gamma rays emitted: 10
~106 gamma/second
Ge det. status at glanceGe 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 21Total 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)
Target chamber for in-beam experiments Target chamber for in-beam experiments with with Hyperball2Hyperball2 at CYRIC at CYRIC
Important theme of nuclear structure Important theme of nuclear structure studiesstudies
Nuclear deformationNuclear deformation
• Spontaneous symmetry breaking
• Collective degree of freedom – Nuclear Shape
• Coupling of single particle degree and collective degree of freedom
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132Ce
RotationRotation
Unique Parity OrbitUnique Parity Orbit
SHO SHO+l•sN=0
N=1
N=2
N=3
N=4
N=5•Simple Harmonic Oscill.
(SHO)=(-1)N
•SHO+l•s Major shell consisting of majorities of normal parity and unique parity orbitals.
•The h11/2h11/2 confg.is comprised of two unique parity orbitals.
0s 0s0s1/2
Possible realization for chiral geometry:Possible realization for chiral geometry:
odd-odd nuclei in the A~130 regionodd-odd nuclei in the A~130 regionj
j
R
long
intmd.
short•Z=~55 N=~75•Triaxial mass distribution (shape).•Fermi level lies
low in proton h11/2 subshell,high in neutron h11/2 subshell.
•Collective rotation of triaxial rotor with irrotational flow moment of inertia.
Chiral Geometry in NucleiChiral Geometry in Nuclei
K.Starosta Phys. Rev. Lett. 86, 971 (2001).
Mutually orthogonal coupling of three angular momentain odd-odd nuclei
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