RIKEN Accel. Prog. Rep. 48 (2015)

Ⅱ-1. Nuclear Physics

Parity-transfer reaction for study of spin-dipole 0− mode
M. Dozono,∗1 K. Fujita,∗2 N. Fukuda,∗3 M. Ichimura,∗3 N. Inabe,∗3 S. Kawase,∗1 K. Kisamori,∗1 Y. Kiyokawa,∗1K. Kobayashi,∗4 M. Kobayashi,∗1 T. Kubo,∗3 Y. Kubota,∗1 C. S. Lee,∗1 M. Matsushita,∗1 S. Michimasa,∗1H. Miya,∗1 A. Ohkura,∗2 S. Ota,∗1 H. Sagawa,∗1,∗5 S. Sakaguchi,∗2 H. Sakai,∗3 M. Sasano,∗3 S. Shimoura,∗1Y. Shindo,∗2 L. Stuhl,∗3 H. Suzuki,∗3 H. Tabata,∗2 M. Takaki,∗1 H. Takeda,∗3 H. Tokieda,∗1 T. Uesaka,∗3T. Wakasa,∗2 K. Yako,∗1 M. Yamagami,∗5 Y. Yanagisawa,∗3 J. Yasuda,∗2 R. Yokoyama,∗1 K. Yoshida,∗3 andJ. Zenihiro∗3
The spin-dipole (SD) 0− excitation has recently attracted theoretical attention owing to its strong relevance in the tensor correlations in nuclei. For example,
self-consistent HF+RPA calculations in Ref.1) predictthat the tensor correlations produce a strong hardening (shifting toward higher excitation energy) eﬀect on
the 0− resonance. It is also predicted that the eﬀect issensitive to the magnitude of the tensor strength. Thus
experimental data of the SD 0− distribution enable us
to examine the tensor correlation eﬀects quantitatively.
Despite this importance, experimental information on
0− states is limited because of the lack of the experimental tools suitable for 0− studies.
We propose a new probe, the parity-transfer(16 O, 16 F(0− , g.s.)) reaction, for 0− studies2) . The
parity-transfer reaction selectively excites unnaturalparity states for a 0+ target nucleus, which is an advantage over the other reactions used thus far. In order toestablish the parity-transfer reaction as a new tool for0− studies, we measured the 12 C(16 O, 16 F(0− , g.s.))12 B
reaction. We demonstrate the eﬀectiveness of this reaction by identifying the known 0− state at Ex =9.3 MeV in 12 B.
The experiment was performed at the RIKEN RI
Beam Factory (RIBF) by using the SHARAQ spectrometer and the high-resolution beam line. Figure 1
shows a schematic layout of the experimental setup. A
primary 16 O beam at 250 MeV/nucleon and 107 pps

from the superconducting RING cyclotron (SRC) wastransported to the S0 target position. The beamline to the spectrometer was set up for dispersionmatched transport. We used a segmented plastic scintillation detector as an active 12 C target. This detector consisted of 16 plastic scintillators with a size of30 mm × 5 mm × 1 mm, and it was used to determine
the x-position of the beam on the target. The outgoing
15O + p particles produced by the decay of 16 F weremeasured in coincidence. The particles were momentum analyzed by using the SHARAQ spectrometer.
The 15 O particles were detected with two low-pressure
multi-wire drift chambers (LP-MWDCs) at the S2 focal plane, while the protons were detected with twoMWDCs at the S1 focal plane.
We reconstructed the relative energy Erel between
the 15 O and the proton. A preliminary result is shownin Fig. 2. The obtained Erel resolution was 150 keV in
FWHM at Erel = 535 keV, and the 0− ground stateof 16 F was clearly separated from other excited states.
In order to identify the 12 B(0− , 9.3 MeV) state, data
analysis for obtaining the 12 C(16 O, 16 F(0− , g.s.)) spectrum and its angular distributions is in progress.

Fig. 2. Preliminary result of the relative energy between
the 15 O nucleus and the proton from the decay of 16 F.

∗1
∗2
∗3
∗4
∗5Fig. 1. Schematic layout of the experimental setup.

References

Center for Nuclear Study, University of Tokyo
Department of Physics, Kyushu University
RIKEN Nishina Center
Rikkyo University
Center for Mathematics and Physics, University of Aizu

1) H. Sagawa and G. Colò: Prog. Part. Nucl. Phys. 76, 76(2014).
2) M. Dozono et al.: RIKEN Accel. Prog. Rep. 45, 10(2012).

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