Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 48 (2015)

Spin-dipole response of 4 He by using (8 He, 8 Li(1+ ))The spin dipole (SD) (∆ S = ∆ L =1) of spin-isospin
responses is connected with the tensor correlation innuclei. Especially, on a double-closed nucleus, the SD
excitation contribution is large because of the nucleon
conﬁguration. The SD excitation function was measured on 4 He which is the lightest double-closed nucleus. This is important for the study of supernova
nucleosynthesis with the neutrino-nucleus reaction1) .
We coducted the exothermic charge-exchange (CE)reaction of 4 He(8 He, 8 Li(1+ ))4 H. CE reactions are
powerful tools to study the spin-isospin responses.
The spin-ﬂip transition of 8 He(0+ ) → 8 Li(1+ ) canbe identiﬁed by measuring the de-excited γ-rays(Eγ =0.98 MeV) from the ﬁrst 1+ state of 8 Li. The
beam energy region of 100–300 MeV/nucleon is suitable for the study of the spin-isospin responses2) .
The experiment was performed at the RIKEN
RIBF facility by using BigRIPS3) , the high-Resolution
beamline4) , and the SHARAQ spectrometer5) . The
8He beam, which was produced via a projectilefragmentation reaction with an 18 O beam and 9 Betarget, was transported to the secondary target position at an intensity of 2 MHz. We used the liquid4
He target6) with a thickness of 120 mg/cm2 . In order to determine the excitation energy using missing
mass method, the momenta of 8 He and 8 Li at an energy of 190 MeV/nucleon were measured at the beamline and SHARAQ within the low-pressure multi-wiredrift chamber (LP-MWDC) 7) and cathode readout
drift chamber8) . The γ-ray detector array DALI29)
was placed around the target position to measure the0.98 MeV γ-ray.
Figure 1 shows the missing mass spectrum of the(8 He,8 Li) reaction (black line). The contribution ofboth the 4 He target and hydrogen is included in this
∗1Center for Nuclear Study, The University of Tokyo
RIKEN Nishina Center∗3 Institut de Physique Nucléaire, Orsay∗4 Department of Physics, Kyoto University∗5 Research Center Nuclear Physics, Osaka University∗6 Cyclotron and Radioisotope Center, Tohoku University∗7 Department of physics, Tokyo Institute of Technology∗8 Department of Applied Physics, University of Miyazaki∗9 National Institute of Radiological Sciences∗10 Department of physics, The University of Tokyo∗11 Department of Physics, Kyushu University∗12 National Superconducting Cyclotron Laboratory, Michigan
State University∗2Counts/2Counts/2 MeV
MeV

H. Miya,∗1 S. Shimoura,∗1 K. Kisamori,∗1,∗2 M. Assié,∗3 H. Baba,∗2 T. Baba,∗4 D. Beaumel,∗3 M. Dozono,∗1T. Fujii,∗2 N. Fukuda,∗2 S. Go,∗1 F. Hammache,∗3 E. Ideguchi,∗5 N. Inabe,∗2 M. Itoh,∗6 D. Kameda,∗2S. Kawase,∗1 T. Kawabata,∗4 M. Kobayashi,∗1 Y. Kondo,∗7 T. Kubo,∗2 Y. Kubota,∗1,∗2 C. S. Lee,∗1,∗2Y. Maeda,∗8 H. Matsubara,∗9 S. Michimasa,∗1 K. Miki,∗5 T. Nishi,∗10 M. Kurata-Nishimura,∗2 S. Ota,∗1H. Sakai,∗2 S. Sakaguchi,∗11 M. Sasano,∗2 H. Sato,∗2 Y. Shimizu,∗2 H. Suzuki,∗2 A. Stolz,∗12 M. Takaki,∗1H. Takeda,∗2 S. Takeuchi,∗2 A. Tamii,∗5 H. Tokieda,∗1 M. Tsumura,∗4 T. Uesaka,∗2 K. Yako,∗1 Y. Yanagisawa∗2and R. Yokoyama∗1303025252020151510105500-30 -20-20 -10-10-3000

1010202030 40
40 50
50 6060 707030
Excitation energy
energy [MeV][MeV]
Excitation

Fig. 1. Excitation energy distribution of 4 H obtained using missing mass method. The red line shows the background estimated from the contamination of the excitation energy distribution.

spectrum. The region around 10 MeV and −17 MeV
shows the 4 He →4 H and 1 H → n reactions, respectively. The 1 H → n reaction originates at the plastic
scintilator installed at the upstream of the target. The
amount of contamination (red line) was estimated byusing the energy loss of the LP-MWDC placed between
the scintilator and the target. Thus, the 4 He(8 He,8Li)4 H reaction was obtained.
Further analysis to obtain the angular distribution
and double diﬀerential cross-sections is now in progress
to obtain the isovector SD strength of 4 He.
References
1) T. Suzuki et al. Phys. Rev. C 74, 034307 (2006).
2) W. G. Love and M. A. Franey: Phys. Rev. C 24, 1073
(1981).
3) T. Kubo et al.: Nucl. Instr. Meth. B 204, 97-113 (2003).
4) T. Kawabata et al.: Nucl. Instr. Meth. B 266, 4201-4204(2008).
5) S. Michimasa et al.: Nucl. Instr. Meth. B 317, 305-310(2013).
6) H. Ryuto et al: Nucl. Instr. Meth. A 555, 1-5 (2005).
7) H. Miya et al.: Nucl. Instr. Meth. B 317, 701-704 (2013).
8) K. Kisamori et al.: CNS Ann. Rep. 2011 (2013).
9) T. Takeuchi et al.: Nucl. Instr. Meth. A 763, 1-8 (2014).

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