Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 49 (2016)

TZ = −1 and TZ = −2 β-decay studies using 78 Kr fragmented beams
at BigRIPS, part I
B. Rubio,¤1 J. Agramunt,¤1 A. Algora,¤1 V. Guadilla,¤1 A. Montaner-Piza,¤1 A. I. Morales,¤1 S. E. A. Orrigo,¤1J. Chiba,¤2 D. Nichimura,¤2 H. Oikawa,¤2 Y. Takei,¤2 S. Yagi,¤2 B. Blank,¤3 P. Ascher,¤3 M. Gerbaux,¤3T. Goigoux,¤3 J. Giovinazzo,¤3 S. Gre¶vy,¤3 T. Kurtukian Nieto,¤3 C. Magron,¤3 P. Aguilera,¤4 F. Molina,¤4D. S. Ahn,¤5 P. Doornenbal,¤5 N. Fukuda,¤5 N. Inabe,¤5 G. Kiss,¤5 T. Kubo,¤5 S. Kubono,¤5 S. Nishimura,¤5Y. Shimizu,¤5 C. Sidong,¤5 P. A. SoÄderstroÄm,¤5 T. Sumikama,¤5 H. Suzuki,¤5 H. Takeda,¤5 P. Vi,¤5 J. Wu,¤5Y. Fujita,¤6 M. Tanaka,¤6 W. Gelletly,¤1,¤7 F. Diel,¤8 D. Lubos,¤9 G. de Angelis,¤10 D. Napoli,¤10 C. Borcea,¤11A. Boso,¤12 R. B. Cakirli,¤13 E. Ganioglu,¤13 G. de France,¤14 and S. Go¤15
The study of the beta decay of proton-rich nuclei isinteresting for a number of reasons; we can have access to states in the daughter nucleus populated byFermi (the Isobaric Analogue State, IAS) as well as
Gamow-Teller transitions and in some cases the IAS isfragmented (see for instance1) and2) ); it can also happen that the process goes via the exotic beta-delayed
gamma-proton decay, a phenomenon that is the resultof a combined effect of the forbidden proton decay ofthe IAS and the fact that some of the states populated
after γ-decay are proton-unbound. Furthermore, spinisospin excitations can be studied by beta-decay andcharge exchange reactions in mirror nuclei, shedding
light on mirror symmetry, hence we can compare ourresults on the beta decay of proton-rich nuclei with theresults of charge exchange experiments when appropriate targets for the mirror nuclei are available3) .
Accordingly we have performed experiments at GSI
and GANIL to study TZ = −14) and TZ = −21) nuclei
respectively where it became clear that the study ofheavier, more exotic systems, demands beam intensities available only at the RIKEN Nishina Center.
The experiment was carried out using the fragmentation of a 345 MeV·A 78 Kr beam with unprecedentedintensity (up to 300 particle nA) on a Be target.
The fragments were separated in flight using the BigRIPS separator5) and implanted in three 1mm thick
WAS3ABi6) double-sided Si strip detectors (DSSSD)
with each of them having an active area of 60 ×40 mm2 segmented into 60 vertical by 40 horizontal
strips. The implantation setup was surrounded by theEUROBALL-RIKEN Cluster Array (EURICA)7) con-Fig. 1. Particle Identification Plot for isotopes at the firstBigRIPS setting, see text.

sisting of 12 HPGe CLUSTER-detectors of Euroballtype. Two different settings of BigRIPS were used inthis experiment, the first was optimised for the production of 58 Zn, 60 Ge, 62 Ge and 64 Se nuclei and overlapped with the experiment planned for the search of
new isotopes and two-proton emitters, see the contribution by B. Blank et al. to this volume, and thesecond for 66 Se. Putting conditions on the ToF and∆E signals of the ions we have produced the identification plot shown in Figure 1 for the first setting. TheY-axis represents the Z of the implanted ion and theX-axis the A/Q. Preliminary results of the analysis arepresented in the second contribution to this progress
report.
References
1) S.E.A. Orrigo et al., Phys. Rev. Lett. 112, 222501(2014).
2) M. MacCormick and G. Audi, Nucl. Phys A 925, 1151
61 (2014).
3) Y.Fujita, B.Rubio and W.Gelletly, Prog. Part. Nucl.
Phys. 66, 549 (2011).
4) F. Molina et al., Phys. Rev. C 91, 014301 (2015).
5) T. Kubo et al., Prog. Theor. Exp. Phys. 2012 03C003(2012).
6) S. Nishimura et al., RIKEN Accel. Progr. Rep. 46, 182(2013)
7) P.-A. Söderström et al., Nuclear Instruments and Methods in Physics Research B 317 (2013) 649652∗1IFIC, CSIC-Univ. Valencia
Tokyo Univ. Sci∗3 CEN Bordeaux-Gradignan∗4 CCHEN-Chile∗5 RIKEN Nishina Center∗6 Osaka University∗7 Surrey University∗8 Universität zu Köln∗9 Technische Universität München∗10 INFN-Legnaro∗11 IFIN-HH, Bucarest∗12 INFN-Padova∗13 Univ. Istanbul∗14 GANIL-France∗15 Univ. Tenesse∗2- 27 -