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)
Chirality
[O , H ]  0,
H | R    R | R  , H | L   L | L  ,
| R   O | L ,| L   O | R ,
 R  L
1
(| R  | L  ),
2
i
| IM  
(| R  | L  ),
2
H | IM    IM | IM  ,
| IM  
O | IM  | IM  ,
 IM   IM.
134Pr
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~80 (unexplored)
Odd-Odd (pg9/2ng9/2)
80Br(?),
Odd-A (p(g9/2)2n(g9/2))
79Kr(?)
A~190
Odd-Odd (ph9/2ni13/2)
188Ir (D. L. Balabanski et. al.,Phys.
Rev. C 70, 044305 (2004))
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
Doublet bands in odd-even 13560Nd75
Energy [MeV]
S. Zhu et al., PRL 91(2003) 132501.
Spin [ħ]
Doublet bands in 10545Rh60
J. Timar et al., PLB598,178 (2004).
Energy [MeV]
8
6
4
2
0
4
8
12
16
Spin [ħ]
20
24
Possible chiral structure in 79Kr
p(g9/2)2ng9/2
G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)
Hyperball2 experiment @ 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 ]
x6
→ Photopeak efficiency ~ 5% at
1 MeV
 UMEM/Double buffering
70Zn
+ 13C
79Kr
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 shifts
equivalent to 72 g-g unfolded event
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
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
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)
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
Rate 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 glance
• Eurisys Single Crystal Ge (r.e. ~60%) X 5
• Ortec Single Crystal Ge (r.e. ~60%) X 10
• Eurisys Clover type Ge
X6
– (r.e. ~20%, add-back 125%)
Total
Ready for use
Being Repaired
X 21
X 12
X 6
(G2,G3,G14,S/N1,S/N3,S/N4)
Problematic
(G1,G9,G1)
X 3
Target chamber for in-beam experiments
with Hyperball2 at CYRIC
Important theme of nuclear structure
studies
Nuclear deformation
• Spontaneous symmetry breaking
• Collective degree of freedom
– Nuclear Shape
• Coupling of single particle degree and
collective degree of freedom
R ()
Rotation
[ R (), H ]  0,
H | 0    0 | 0    0 |  () ,
|  ()  R () | 0 .
| IM    f () |  () d,
H | IM    0 | IM ,
| IM   R() | IM .
| 0 
|  ()
132Ce
Unique Parity Orbit
•Simple Harmonic Oscill.
(SHO)
p=(-1)N
•SHO+l•s
N=5
N=4
Major shell consisting of N=3
majorities of normal parity
and unique parity orbitals.
N=2
•The ph11/2nh11/2 confg.
is comprised of two
unique parity orbitals.
N=1
N=0
0s
SHO
0s
0s1/2
SHO+l•s
Possible realization for chiral geometry:
odd-odd nuclei in the A~130 region
intmd.
R
•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.
jp
short
jn
long
Chiral Geometry in Nuclei
Mutually orthogonal coupling of three angular momenta
in odd-odd nuclei
K.Starosta Phys. Rev. Lett. 86, 971 (2001).