Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 50 (2017)

Parity-transfer (16 O, 16 F(0− )) reaction
to study spin-dipole 0− states
M. Dozono,∗1 T. Uesaka,∗2 N. Fukuda,∗2 M. Ichimura,∗2 N. Inabe,∗2 S. Kawase,∗1 K. Kisamori,∗1Y. Kiyokawa,∗1 K. Kobayashi,∗3 M. Kobayashi,∗1 T. Kubo,∗2 Y. Kubota,∗1 C. S. Lee,∗1 M. Matsushita,∗1S. Michimasa,∗1 H. Miya,∗1 A. Ohkura,∗4 S. Ota,∗1 H. Sagawa,∗2,∗5 S. Sakaguchi,∗4 H. Sakai,∗2 M. Sasano,∗2S. Shimoura,∗1 Y. Shindo,∗4 L. Stuhl,∗2 H. Suzuki,∗2 H. Tabata,∗4 M. Takaki,∗1 H. Takeda,∗2 H. Tokieda,∗1T. Wakasa,∗4 K. Yako,∗1 Y. Yanagisawa,∗2 J. Yasuda,∗4 R. Yokoyama,∗1 K. Yoshida,∗2 and J. Zenihiro∗2in the (d, 2 He) data. This enhancement is due to theknown 0− state at Ex = 9.3 MeV. These diﬀerences inFig. 1 indicate that the parity-transfer reaction has ahigh selectivity to 0− states. The feature will be conﬁrmed by further discussions including angular distributions and DWBA calculations in our future publication.

We proposed a new reaction probe, parity-transfer(16 O, 16 F(0− , g.s.)) reaction, as a powerful tool tostudy spin-dipole (SD) 0− states in nuclei1) . This
reaction has a unique selectivity to unnatural-parity
states, which is an advantage over the other reactions used thus far. As the ﬁrst measurement, the12C(16 O, 16 F(0− )) reaction at 247 MeV/u was studied
in the SHARAQ08 experiment at RIBF. A known 0−state at Ex = 9.3 MeV in 12 B2) serves as a benchmark
to verify the eﬀectiveness of this reaction. The detailsof the experimental setup and method can be found inRef.3) .
The results of the present study are currently being prepared for publication. In this report, we discuss the selectivity of the parity-transfer reaction to 0−states by comparing our data with that previously obtained by the 12 C(d, 2 He) reaction at 270 MeV4) . Figures 1(a) and 1(b) show excitation energy (Ex ) spectra
for the 12 C(16 O, 16 F(0− )) reaction at θlab = 0◦ − 0.25◦
and 0.25◦ − 0.45◦ , respectively. The energy resolution is 2.6 MeV in FWHM. Note that the events atEx ∼ −10 MeV are due to hydrogens in the target.
The 12 C(d, 2 He) spectra at θcm = 0◦ − 1◦ and 6◦ − 8◦are shown as dashed curves in Figs. 1(a) and 1(b),respectively. Here, the momentum transfer is comparable to that of our data in each ﬁgure. (Their values
are q ∼ 0.3 and 0.5 fm−1 in Figs. 1(a) and 1(b), respectively). Solid curves represent the (d, 2 He) cross sections after smearing with an energy resolution of thepresent experiment. The (d, 2 He) spectra have been
arbitrarily normalized to the (16 O, 16 F(0− )) cross sections for the 1+ g.s.
The excitation of the 1+ g.s. and the 2− state at
Ex = 4.4 MeV can be seen in both reaction data,while the structures at Ex  6 MeV are largely different. A bump structure at Ex = 7.5 MeV (“A” inFig. 1(b)) seen in the (d, 2 He) reaction is missing inthe (16 O, 16 F(0− )) spectra. This is because naturalparity states are not populated with the parity transfer reaction. Another striking diﬀerence is a peak atEx ∼ 9 MeV observed in Fig. 1(a); a clear enhancement appears in the (16 O, 16 F(0− )) data but vanishes∗1∗2∗3∗4∗5Fig. 1. Excitation energy spectra for the 12 C(16 O, 16 F(0− ))reaction. The dashed and solid curves represent theexperimental data for the 12 C(d, 2 He) reaction4) .

References
1) M. Dozono et al., RIKEN Accel. Prog. Rep. 45, 10(2012).
2) H. Okamura et al., Phys. Rev. C 66, 054602 (2002).
3) M. Dozono et al., Nucl. Instrum. Meth. A 830, 233(2016).
4) H. Okamura et al., Phys. Lett. B 345, 1 (1995).

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

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