Search for chiral doublet structures Search for chiral doublet structures in mass A~80 region: in mass A~80 region:

odd-A odd-A 7979Kr and odd-odd Kr and odd-odd 8080BrBrwith the Hyperball2 array @ CYRICwith the Hyperball2 array @ CYRIC

CYRIC @Tohoku UniversityDept. 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)

Rh IsotpesRh Isotpes

intmd.

jlong

short

R j

intmd.

jlong

short

R j

Odd-A

Odd-Odd

J. Timar et al. to be submitted.

A~130Odd-Odd (h11/2h11/2

-1)132Cs,130Cs,128Cs,126Cs,124Cs134La,132La,130La134Pr,132Pr136Pm140Eu,138EuOdd-A ((h11/2)2h11/2

-1)135Nd,135Ce

A~105Odd-Odd (g9/2

-1h11/2)106Ag,106Rh,104Rh,102Rh100TcOdd-A (g9/2

-1(h11/2)2)107Ag,105Rh, 103Rh

A~190Odd-Odd (h9/2i13/2)188Ir

A~80 (unexplored)Odd-Odd (g9/2g9/2

-1)80Br(?),Odd-A ((g9/2)2g9/2

-1)79Kr(?)

Even-Even (h11/2(d5/2,g7/2)(h11/2)2)136Nd

Possible chiral structure in Possible chiral structure in 7979KrKr

G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)

(g9/2)2g9/2

50%

5~10%

1~2.5%

79

A Road to HB2 experiment at CYRICA Road to HB2 experiment at CYRIC

• 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 coincidence run

7070Zn(Zn(1313C,xnypzC,xnypz))

coincidence measurementcoincidence measurement with Stony Brook array

(6 Compton suppressed Ge dets.)

827

1026

827

1026

1144

1154

1144

700

559

Hyperball2 runHyperball2 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

Hyperball2 array performanceHyperball2 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

10261144

827

Performance improvementPerformance 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

Proposed experiment with Proposed experiment with the Hyperball2 arraythe Hyperball2 array

• 70Zn(13C,4n)79Kr @ 65MeV• Pb backed 1mg/cm2 70Zn target (ready)

– Reduction of Doppler broadening

• ~200K counts for 827keV peak X 6=1.2M– 1.2MX0.01=12K12K for the transitions of interests

in 1212 shifts with triple coincidence measurement

• 3 shifts for 80Br test run with the same reaction but lower energy @55MeV

Total of 15 shiftsTotal of 15 shifts

7070Zn + Zn + 1313CC

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

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

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]

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]

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

Possible chiral structure in Possible chiral structure in 7979KrKr

G.D. Johns et. al, Phys. Rev. C 50,2786 (1994)

(g9/2)2g9/2

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

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

LR

LR

ROLLOR

LLRR

O

,||,||

,||,||

,0],[

HH

H

IMIM

IM

IMIM

IMIMH

iIM

IM

.

,||

,||

),|(|2

|

),|(|2

1|

O

LR

LR

134Pr

ChiralityChirality