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Spectroscopy studies by decay Proton-rich nuclei N~Z Deformation in the mass region A~75 Fundamental aspects of weak interaction, test of CVC Neutron-rich nuclei Z~20 effective interaction in the mass region A~50. C écile Jollet, IReS Strasbourg, TAS Workshop, Caen March 31, 2004.
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Spectroscopy studies by decay • Proton-rich nuclei N~Z • Deformation in the mass region A~75 • Fundamental aspects of weak interaction, test of CVC • Neutron-rich nuclei Z~20 • effective interaction in the mass region A~50 Cécile Jollet, IReS Strasbourg, TAS Workshop, Caen March 31, 2004
Nuclear structure Nucleosynthesis Exploration of nuclei with large Q value (nuclei far from stability) Provides the first information on new species Fundamental aspects of weak interaction decay: general features Spectroscopy detection of, and delayed particules (neutrons or protons, and -rays) Informations provided: Mass excess Half-life T1/2 feedings I ft = f(Z,Q-Ex) T1/2 / I ft = Cste / |Mif|2 Matrix elements, nuclear configurations
1-Proton-rich nuclei N~Z, A~75 Theoretical and experimental works in this region shape isomerism or shape coexistence strongly deformed ground states Hamamoto, Sarriguren Shape of the GT strength distribution depends on the shape of parent nucleus ground state • In this region, large part of the GTGR is accessible by decay • Estimate the deformation by measuring the complete B(GT) distribution Good efficiency for detection on the whole QEC window construction of a new Total Absorption gamma Spectrometer (TAgS) Installation of TAgS at ISOLDE in 2001 Study by decay: 72,73,74,75Kr and 76,77,78Sr Detection: TAgS + Ge detectors (X, ) and plastic scintillators () I. Hamamoto et X. Z. Zhang, Z. Phys. A353 (1995) 145.
Boron polyethylene:10cm Lead:5cm Copper:2cm Aluminium:2cm Shielding Ancillary X, , detectors Collection point Tape transport system Total Absorption gamma Spectrometer (TAgS) (Madrid,Strasbourg, Surrey, Valence) NaI monocrystal(diameter=38cm, length=38cm) +8 PMTs 5” TAgS properties: Energy resolution: 7.1% at 662 keV 5.4% at 1332 keV Efficiency at 662 keV: 95(8)% total 83(7)% photopeak Solid Angle: 97% of 4 New beam line
b+ EC b+ EC 74Kr --------> 74Br 76Sr --------> 76Rb oblate prolate exp. 1-Proton-rich nuclei N~Z, A~75 E. Poirier et al., PRC69,034307 (2004) E. Nácher et al., submitted to PRL Shape mixing Prolate shape • Results in good agreement with theory and with previous experiments • decay studies value and sign of the deformation validation of TAgS spectroscopy
Present results 42Sc 3080 • for A=10-54, Ft=3072.3(2.0) s • with precisions: 3.10-4 for T1/2 • 3.10-4for branching ratios • 5.10-5for energy • In progress, new measurements for A>54 66As 10C Ft (s) 50Mn Ft (s) 86Tc 54Co 70Br 38K 82Nb 26Al 46V 3070 88Y 34Cl 14O 3065 Z 62Ga 74Rb g 9/2 1- Proton-rich nuclei N~Z Fundamental aspect of weak interaction V-A theory, hyp: the Vector Current is conserved (CVC) vector part of weak interaction not influenced by strong interaction To test CVC: study of superallowed Fermi transitions 0+0+ Ft = ft (1+r) (1-c) = cste (r, c are correction terms) We need to determine the complete decay scheme, r and c TAgS measure branching ratios and T1/2 with the required precision Current measurement with TAgS : study of 62Ga
(F. Perrot thesis) 51, 52, 53 K (1/2,3/2+) (2-) (3/2+) allowed Q~14-16 MeV delayed neutrons forbidden GT Sn~3.5-4.5 MeV nat gs 51, 52, 53 Ca (3/2-) (0+) (3/2-) Allowed GT transitions non natural parity states forbidden GT transitions natural parity states Ex>4 MeV (above Sn) f5/2 f5/2 x x x x p1/2 p1/2 fp shell x x x x xx x x x x x x x x x p3/2 p3/2 f7/2 f7/2 d3/2 d3/2 x sd shell 52K33 52K33 52Ca32 52Ca32 p-n interaction across sd-fp shell n-n interaction across fp shell 20 19 20 19 2-Neutron-rich nuclei A~50, Z~20 Neutron-rich nuclei large Q-Sn energy window We need efficient neutron and gamma detection direct knowledge of I, Pxn and Ex Non nat
2-Neutron-rich nuclei A~50, Z~20 TONNERRE Detector (LPC Caen, IFIN Bucarest) En= 0.2-7 MeV ~ 11% at 1 MeV Experimental setup at ISOLDE Low energy neutron detectors (x8) (IReS) En = 0.05-3.0 MeV ~ 0.5% at 1 MeV Ge Clusters (x2) (MINIBALL collaboration) ~ 5% at 1.3 MeV and 4 (start n-TOF) ~ 70%
b- b- 52K --------> 52Ca 53K --------> 53Ca 2-Neutron-rich nuclei A~50, Z~20 Preliminary results In red: new transitions In green: new neutron emitter states and transitions 52K decay detection of both low and high energy neutrons 53K decay only part of the statistics Comparison with theory for 51,52,53Ca in progress (E. Caurier, F. Nowacki, IReS)
Conclusions & Perspectives We have 2 experimental setup which are performing to explore the nuclear structure: TAgS LEND-TONNERRE coupling Efficient neutron detection Effective interaction, shell order Neutron-rich nuclei near the closed shell 35,36Al, Cu, Zn… High efficiency study of N~Z nuclei deformation A~80 CVC test 74Rb … mirror decays 71Kr, 75Sr Such investigations can be performed using any low energy beams at ISOLDE, Ganil, Alto…
Production yield information ISOLDE :http://isolde.web.cern.ch/isolde/ Ulli Koster SPIRAL: http://www.ganil.fr/operation/available_beams/ radioactive_beams.htm ALTO: Fadi Ibrahim (preliminary estimation)
Collaboration • Algora J.C. Angélique G. Ban P. Baumann F. Benrachi C. Borcea • M.J.G. Borge A. Buta D. Cano-Ott J.C Caspar E. Caurier S. Courtin • P. Dessagne J. Devin D. Etasse L.M. Fraile F. Perrot W. Gelletly S. Grévy • G. Heitz C. Jollet A. Jungclaus F.R. Lecolley E. Liénard G. Le Scornet • F. Maréchal C.Miéhé E. Nacher F. Negoita F. Nowacki N. Orr E. Poirier • M. Ramdhane B. Rubio M.D. Salsac P. Sarriguren J.L. Tain O. Tengblad • C. Weber • The IReS workshop and the ISOLDE Collaboration