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

.

,||

,||

),|(|2

|

),|(|2

1|

O

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

.|)()(|

,)(|||

,0]),([

0

0000

R

H

HR

.|)(|

,||

,)(|)(|

0

IMRIM

IMIMH

dfIM

0| )(|

)(R

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