Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 50 (2017)

Beta-delayed proton spectrum from the Tz = −2 nucleus 64 Se atBigRIPS501587(31)Counts / 20 keV

Spin-isospin excitations can be studied by β-decay
and charge exchange reactions in mirror nuclei, shedding light on mirror symmetry. Hence we can compare
our results on the β decay of proton-rich nuclei withthe results of charge exchange experiments when appropriate targets for the mirror nuclei are available1) .
Accordingly we have performed experiments at GSI
and GANIL to study Tz = −12) and Tz = −23,4) nuclei respectively where it became clear that the studyof heavier, more exotic systems demands beam intensities available only at the RIKEN RIBF.
We have performed an experiment using the fragmentation of a 345-MeV/nucleon 78 Kr beam with atypical intensity of 200 pnA on a Be target. The fragments were separated in ﬂight using the BigRIPS separator and implanted in three WAS3ABi double-sided
Si strip detectors (60 mm × 40 mm × 1 mm, 60 horizontal and 40 vertical strips). The implantation setup
was surrounded by the EUROBALL-RIKEN Cluster
Array (EURICA). The experiment is described in detail in a previous report.5)
Here we present the ﬁrst experimental observation of
the beta-delayed protons in the decay of the Tz = −264
Se nucleus. The spectrum was constructed using
time correlations between 64 Se implantations and allβ signals within a single pixel, deﬁned as the crossingof one X and one Y strip. Fig. 1 shows the β-delayed
proton spectrum of 64 Se. The proton energies were obtained by ﬁtting the previously known β-delayed proton response function in DSSSD detectors, detailed inRef.4) , consisting of a Gaussian function plus an expo-40

2001(22) (IAS)P. Aguilera,∗1 F. Molina,∗1 B. Rubio,∗2 J. Agramunt,∗2 A. Algora,∗2 V. Guadilla,∗2 A. Montaner-Piza,∗2
A. I. Morales,∗2 S. E. A. Orrigo,∗2 B. Blank,∗3 P. Ascher,∗3 M. Gerbaux,∗3 T. Goigoux,∗3 J. Giovinazzo,∗3S. Grévy,∗3 T. Kurtukian Nieto,∗3 C. Magron,∗3 D. Nishimura,∗4 J. Chiba,∗4 H. Oikawa,∗4 Y. Takei,∗4 S.Yagi,∗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. Söderström,∗5 T. Sumikama,∗5 H. Suzuki,∗5 H. Takeda,∗5 P. Vi,∗5 J. Wu,∗5∗6
∗6
∗2,∗7
∗10
∗11Y. Fujita,∗6Tanaka,∗6W. Gelletly,Gelletly,∗2C.
M. Tanaka,W.
,∗7 F. Diel,∗8 D. Lubos,∗9 G. de Angelis,∗10 D.
D. Napoli,
Napoli,∗10C. Borcea,
Borcea,∗11∗12
∗15
∗12
∗13
∗13
∗14
∗15
E. Ganioglu,
G. de France,and S. Go
A. Boso,R. B. Cakirli,Go,

10001000

2000

3000

4058(102)203283(27)1188(53)304000

5000

6000

Energy [keV]

Fig. 1. β-delayed proton spectrum of 64 Se. The dashedblue lines represent the individual proton response functions. The numbers above the proton peaks indicate theproton energy after a shift correction has been applied(see text).

nential tail. The WAS3ABi DSSSD detectors were calibrated using an external electron conversion in a 207 Bi
source; thus proton energy shifts are expected. Theseenergy shifts were compared and recalibrated using the57
Zn and 61 Ge beta-delayed proton spectra obtained inthis experiment and constructed in the same manneras the 64 Se beta-delayed proton spectrum. The 57 Znand 61 Ge proton energies are taken from Ref.6) . The
uncertainties in the proton energies shown in Fig. 1
originate from the ﬁt of the response function for each
proton peak as well as the systematic shift of the proton energies compared with those reported in the literature.6)∗1

Chilean Nuclear Energy Commision
IFIC, CSIC-Universidad de Valencia∗3 Centre d’Etudes Nucléaires de Bordeaux-Gradignan∗4 Department of Physics, Tokyo City University∗5 RIKEN Nishina Center∗6 Department of Physics, Osaka University∗7 Department of Physics, Surrey University∗8 Institute of Nuclear Physics, Universität zu Köln∗9 Physics Department E-12, Technische Universität München∗10 Istituto Nazionale di Fisica Nucleare, Laboratorio Nazionale
di Legnaro∗11 National Institute for Physics and Nuclear Engineering,
IFIN-HH∗12 Istituto Nazionale di Fisica Nucleare, Sezione di Padova∗13 Department of Physics, Istanbul University∗14 Grand Accélérateur National d’Ions Lourds∗15 Department of Physics, Tennessee University∗2References
1) Y. Fujita, B. Rubio, W. Gelletly, Prog. Part. Nucl. Phys.
66, 549 (2011).
2) F. Molina et al., Phys. Rev. C 91, 014301 (2015).
3) S. E. A. Orrigo et al., Phys. Rev. Lett. 112, 222501(2014).
4) S. E. A. Orrigo et al., Phys. Rev. C 93, 044336 (2016).
5) B. Rubio et al., RIKEN Accel. Prog. Rep. Vol. 49 27(2015).
6) B. Blank et al.: Eur. Phys. J. A 31, 267 (2007).

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