Recoil-beta tagging

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Recoil-beta tagging David Jenkins

description

Recoil-beta tagging. David Jenkins. Odd-odd N=Z. Fascinating laboratory for studying interplay of T=0 and T=1 states Very unusual low level density for odd-odd nuclei e.g. only 1 state below 1 MeV in 70 Br Evidence for np-pairing in both low lying states and high spin rotational bands - PowerPoint PPT Presentation

Transcript of Recoil-beta tagging

Page 1: Recoil-beta tagging

Recoil-beta taggingRecoil-beta tagging

David JenkinsDavid Jenkins

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Odd-odd N=ZOdd-odd N=Z

Fascinating laboratory for Fascinating laboratory for studying interplay of T=0 and studying interplay of T=0 and T=1 statesT=1 states

Very unusual low level Very unusual low level density for odd-odd nuclei density for odd-odd nuclei e.g. only 1 state below 1 MeV e.g. only 1 state below 1 MeV in in 7070BrBr

Evidence for np-pairing in Evidence for np-pairing in both low lying states and high both low lying states and high spin rotational bandsspin rotational bands

Beta decays important for Beta decays important for standard model tests - CVC standard model tests - CVC hypothesishypothesis

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How to study odd-odd N=ZHow to study odd-odd N=Z

Nuclei are difficult to produce without reactions close to 40Ca+40Ca at near-barrier energies

Production cross-sections are low (<1% of total cross-section) Residues are too slow at focal plane of separator e.g. FMA to use ion

chamber to identify Z Most measurements done with neutron detectors + charge particle

detectors to select e.g. pn or pn channel

Nuclei are difficult to produce without reactions close to 40Ca+40Ca at near-barrier energies

Production cross-sections are low (<1% of total cross-section) Residues are too slow at focal plane of separator e.g. FMA to use ion

chamber to identify Z Most measurements done with neutron detectors + charge particle

detectors to select e.g. pn or pn channel

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Recoil-decay taggingRecoil-decay tagging

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Recoil-beta taggingRecoil-beta tagging

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RITU+GREATRITU+GREAT

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Test case: 74RbTest case: 74Rb

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Proof-of-principleProof-of-principle

natCa (36Ar, pn) 74Rb Ebeam = 103 MeV τ½ (74Rb) = 65 ms β+

endpoint ~ 10 MeV σ ~ 10 μb

natCa (36Ar, pn) 74Rb Ebeam = 103 MeV τ½ (74Rb) = 65 ms β+

endpoint ~ 10 MeV σ ~ 10 μb

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High energy positrons

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Varying the beta gate sizeVarying the beta gate size

1 10 MeV

3 10 MeV

6 10 MeV

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Identification of 74RbIdentification of 74Rb

A.N. Steer, et al., NIM A565, 630 (2006)

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74Rb level scheme from RBT74Rb level scheme from RBT

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Unknown case:78YUnknown case:78Y

Nothing known about 78Y except 0+ superallowed decay and (5+) beta-decaying isomer

RBT technique applied using 40Ca(40Ca,pn)78Y reaction

Cross-section should be very similar to 74Rb

90% of flux proceeds to low-lying isomer

Isomer is too long-lived for effective tagging

Nothing known about 78Y except 0+ superallowed decay and (5+) beta-decaying isomer

RBT technique applied using 40Ca(40Ca,pn)78Y reaction

Cross-section should be very similar to 74Rb

90% of flux proceeds to low-lying isomer

Isomer is too long-lived for effective tagging

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B.S. Nara Singh et al., Phys. Rev. C (accepted)

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Coulomb Energy Differences

Extremely sensitive to nuclear structure effects:

•Rotational alignment mechanism •Correlations of pairs of particles •Changes in deformation•The evolution of nuclear radii D.D. Warner et al., Nature Physics 2, 311 (2006)

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CEDs for A~70

Difference in np and NN pairs gives CED rise of ~12 keV/J

Uniform upward trend for deformed nuclei except:

A=78 - flat

A=70 - strongly down

A=70 data from G. de Angelis, EPJ A12, 51 (2001) and

D.G. Jenkins et al., PRC 65, 064307 (2002)

CED(J)=Ex(J,T=1,Tz<)-Ex(J,T=1,Tz>)

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Effect of shape changeEffect of shape change

2=-0.3 2=0.35

2=0.18 2=0.35

CED=-7 keV

CED=-75 keV

R. Sahu et al., J. Phys. G 13, 603 (1987)

TRS calculations: T. Mylaeus et al., J. Phys. G 15, L135 (1989)

Coulomb energies calculated after S. Larsson, Phys. Scri 8, 17 (1973).

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Plans for future measurementsPlans for future measurements

Recoil-beta-tagging: Search for Tz=-1 nuclei e.g.70Kr, 74Sr using double-beta-tagging

Study mirror symmetry in A=71 i.e. 71Kr Search for 0+ in 74Rb and compare B(E0) with 74Kr Use vacuum-mode recoil separator to select by mass and improve

rates

Recoil-beta-tagging: Search for Tz=-1 nuclei e.g.70Kr, 74Sr using double-beta-tagging

Study mirror symmetry in A=71 i.e. 71Kr Search for 0+ in 74Rb and compare B(E0) with 74Kr Use vacuum-mode recoil separator to select by mass and improve

rates

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RBT CollaborationRBT Collaboration

B.S. Nara Singh1, A.N. Steer1, D.G. Jenkins1, R. Wadsworth1, P. Davies1, R. Glover1, N.S. Pattabiraman1, T. Grahn2, P.T. Greenlees2, P. Jones2,

R. Julin2, M. Leino2, M. Nyman2, J. Pakarinen2, P. Rahkila2, C. Scholey2, J. Sorri2, J. Uusitalo2, P.A. Butler3, M. Dimmock3, R. D. Herzberg3,

D.T. Joss3, R.D. Page3, J. Thomson3, R. Lemmon4, J. Simpson4, B. Blank5, B. Cederwall6, B. Hadinia6, M. Sandzelius6

Department of Physics, University of York, Heslington, York YO10 5DD, UK Department of Physics, University of Jyväskylä, P.O. Box 35, FIN-40351, Jyväskylä, Finland Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, UK CCLRC Daresbury Laboratory, Keswick Lane, Warrington WA4 4AD, UK Centre d’Etudes Nuclèaires de Bordeaux-Gradignan, F-33175 Gradignan Cedex, FranceRoyal Institute of Technology, Roslagstullsbacken 21, S-106 91 Stockholm, Sweden.