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

 decay: general features  Exploration of nuclei with large Q value (nuclei far from stability)   Provides the first information on new species  Fundamental aspects of weak interaction Nuclear structure Nucleosynthesis Spectroscopy  detection of , and delayed particules (neutrons or protons, and  -rays)  Informations provided: Mass excess Half-life T 1/2  feedings I  ft = f(Z,Q  -E x ) T 1/2 / I  ft = Cste / |M if | 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 Good efficiency for  detection on the whole Q EC window  construction of a new Total Absorption gamma Spectrometer (TAgS)  Installation of TAgS at ISOLDE in 2001  Study by  decay: 72,73,74,75 Kr and 76,77,78 Sr Detection: TAgS + Ge detectors (X,  ) and plastic scintillators (  ) In this region, large part of the GTGR is accessible by  decay  Estimate the deformation by measuring the complete B(GT) distribution Hamamoto, Sarriguren  Shape of the GT strength distribution depends on the shape of parent nucleus ground state I. Hamamoto et X. Z. Zhang, Z. Phys. A353 (1995) 145.

Total Absorption gamma Spectrometer (TAgS) (Madrid, Strasbourg, Surrey, Valence) NaI monocrystal (diameter=38cm, length=38cm) +8 PMTs 5” Ancillary X, ,  detectors 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  Boron polyethylene:10cm Lead:5cm Copper:2cm Aluminium:2cm Shielding Collection point New beam line Tape transport system

1-Proton-rich nuclei N~Z, A~75 76 Sr > 76 Rb  + EC E. Nácher et al., submitted to PRL E. Poirier et al., PRC69, (2004) 74 Kr > 74 Br  + EC 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 oblate prolate exp.

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 T 1/2 with the required precision Current measurement with TAgS : study of 62 Ga  for A=10-54, Ft=3072.3(2.0) s with precisions: for T 1/ for branching ratios for energy  In progress, new measurements for A>54 Ft (s) 62 Ga 66 As 70 Br 74 Rb 88 Y 82 Nb 86 Tc Z Ft (s) C 14 O 26 Al 34 Cl 38 K 42 Sc 46 V 50 Mn 54 Co Present results g 9/2 

2-Neutron-rich nuclei A~50, Z~20 (F. Perrot thesis) Neutron-rich nuclei  large Q  -S n energy window We need efficient neutron and gamma detection  direct knowledge of I , P xn and E x Allowed GT transitions  non natural parity states d 3/2 f 7/2 p 3/2 p 1/2 f 5/2 x x x  52 K  x x x x 52 Ca x fp shell sd shell E x >4 MeV (above S n ) p-n interaction across sd-fp shell forbidden GT transitions  natural parity states d 3/2 f 7/2 p 3/2 p 1/2 f 5/2 x x x  52 K  x x x x 52 Ca x n-n interaction across fp shell   Non nat 51, 52, 53 K (1/2,3/2 + ) (2 - ) (3/2 + ) 51, 52, 53 Ca (3/2 - ) (0 + ) (3/2 - ) allowed forbidden GT gs Q  ~14-16 MeV S n ~ MeV delayed neutrons nat

TONNERRE Detector (LPC Caen, IFIN Bucarest) E n = MeV  ~ 11% at 1 MeV Low energy neutron detectors (x8) (IReS) E n = MeV  ~ 0.5% at 1 MeV Ge Clusters (x2) (MINIBALL collaboration)  ~ 5% at 1.3 MeV and 4  (start n-TOF)  ~ 70% 2-Neutron-rich nuclei A~50, Z~20 Experimental setup at ISOLDE

In red: new  transitions In green: new neutron emitter states and transitions 52 K decay  detection of both low and high energy neutrons 53 K decay  only part of the statistics Comparison with theory for 51,52,53 Ca in progress ( E. Caurier, F. Nowacki, IReS) 2-Neutron-rich nuclei A~50, Z~20 Preliminary results 52 K > 52 Ca -- 53 K > 53 Ca --

Conclusions & Perspectives High  efficiency study of N~Z nuclei  deformation A~80  CVC test 74 Rb …  mirror decays 71 Kr, 75 Sr 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  35,36 Al, Cu, Zn… Such investigations can be performed using any low energy beams at ISOLDE, Ganil, Alto…

NucleiAat/s ISOLDE Kr Sr Rb Ga NucleiAat/s ISOLDE at/s ALTO K Na Al Ni Cu Zn Sn at/s SPIRAL Production yield information ISOLDE : Ulli Koster SPIRAL: radioactive_beams.htm ALTO : Fadi Ibrahim (preliminary estimation)

Collaboration A.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

Neutrons transmission

Efficiency of neutrons detector : Tonnerre, LEND