II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Gamow-Teller giant resonance in 11 Li neutron drip-line nucleus
L. Stuhl,∗1,∗2,∗3 M. Sasano,∗3 J. Gao,∗3,∗4 Y. Hirai,∗5 K. Yako,∗2 T. Wakasa,∗5 D. S. Ahn,∗3 H. Baba,∗3A. I. Chilug,∗6,∗3 S. Franchoo,∗7 Y. Fujino,∗8 J. Gibelin,∗9 I. S. Hahn,∗1,∗10 Z. Halász,∗11 T. Harada,∗12
M. N. Harakeh,∗13,∗14 D. Inomoto,∗5 T. Isobe,∗3 H. Kasahara,∗5 D. Kim,∗1,∗15 G. G. Kiss,∗11 T. Kobayashi,∗16Y. Kondo,∗17 Z. Korkulu,∗1,∗3 S. Koyama,∗18 Y. Kubota,∗3 A. Kurihara,∗17 H. N. Liu,∗19 M. Matsumoto,∗17S. Michimasa,∗2 H. Miki,∗17 M. Miwa,∗20 T. Motobayashi,∗3 T. Nakamura,∗17 M. Nishimura,∗3 H. Otsu,∗3V. Panin,∗3 S. Park,∗10 A. T. Saito,∗17 H. Sakai,∗3 H. Sato,∗3 T. Shimada,∗17 Y. Shimizu,∗3 S. Shimoura,∗2A. Spiridon,∗6 I. C. Stefanescu,∗6 X. Sun,∗3,∗4 Y. L. Sun,∗19 H. Suzuki,∗3 E. Takada,∗21 Y. Togano,∗8T. Tomai,∗17,∗3 L. Trache,∗6 D. Tudor,∗6,∗3 T. Uesaka,∗3 H. Yamada,∗17 M. Yasuda,∗17 K. Yoneda,∗3 K. Yoshida,∗3J. Zenihiro,∗3 and N. Zhang∗22,∗2
Recent nuclear physics studies are increasingly focused on the region far from the valley of stability,
thereby leading to an increase in the intensity of available exotic isotopes. We started a program1) at theRIKEN Radioactive Isotope Beam Factory with the objective of measuring the spin-isospin responses of lightnuclei along the neutron drip line. There are no available data on nuclear collectivity (giant resonances) onany drip-line nucleus.
In the SAMURAI30 experiment, we studied the mostbasic nuclear collectivity, the Gamow-Teller (GT) giant
resonance, in 11 Li (at 181 MeV/nucleon) and 14 Be (at198 MeV/nucleon) nuclei. The charge-exchange (CE)(p, n) reactions in inverse kinematics are eﬃcient tools
for extracting the B(GT) strengths of unstable isotopes,
up to high excitation energies, without Q-value limitation.2) The uniqe setup of the Particle Analyzer Neutron
Detector Of Real-time Acquisition (PANDORA)3) lowenergy neutron counter + SAMURAI magnetic spectrometer,4) together with a thick liquid hydrogen target
allowed us to perform such measurements with high luminosity and low background. In our previous study on132
Sn, we veriﬁed that with this setup, we can extract
the strength distribution of isovector spin-ﬂip giant resonances in unstable nuclei with quality comparable tothose on stable nuclei.5)
In the 11 Li(p, n)11 Be reaction, we identiﬁed clear kine∗1

Center for Exotic Nuclear Studies, Institute for Basic Science(IBS)∗2 Center for Nuclear Study, University of Tokyo∗3 RIKEN Nishina Center∗4 School of Physics, Peking University∗5 Department of Physics, Kyushu University∗6 Horia Hulubei Nat. Inst. of Phys. and Nucl. Eng.
∗7 Inst. de Physique Nuclaire, Univ. Paris-Saclay∗8 Department of Physics, Rikkyo University∗9 LPC CAEN
∗10 Department of Physics, Ewha Womans University∗11 ATOMKI, Institute for Nuclear Research, HAS∗12 Department of Physics, Toho University∗13 University of Groningen∗14 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗15 Department of Physics, Korea University∗16 Department of Physics, Tohoku University∗17 Dept. of Physics, Tokyo Institute of Technology∗18 Department of Physics, University of Tokyo∗19 Dépt. Physique Nucl., CEA, Univ. Paris-Saclay∗20 Dept. of Physics, Saitama University, Saitama∗21 National Institute of Radiological Sciences (NIRS)∗22 Institute of Modern Physics, Chinese Acad. of Sci.

Fig. 1. Excitation energy spectrum in the 6◦ –8◦ center-ofmass system for 8 Li + t.

matical correlations6) between the neutron energy andlaboratory scattering angle for more than ten diﬀerent
decay channels of 11 Be: 10 Be + n, 9 Be + 2n, 9 Li + p + n,8Li + p + 2n, 9 Li + d, 8 Li + t, 8 Li + d + n, 7 Li + t + n,7Li + d + 2n, 6 Li + t + 2n, α + 6 He + n and 2α + 3n.
The excitation-energy spectra up to approximately
40 MeV have been reconstructed. The background subtraction and acceptance correction are performed. As
an example, Fig. 1 presents the excitation energy spectrum in the daughter nucleus 11 Be for the 8 Li + t decay channel for θC.M. = 6◦ –8◦ . A forward scatteringpeak in the 0◦ –10◦ center-of-mass system indicates astrong GT transition in all decay channles at approximately 19 MeV, below the Isobaric analogue state,7)
which agrees well with previous beta-decay studies.8)
References

1) L. Stuhl et al., RIKEN Accel. Prog. Rep. 48, 54 (2015).
2) M. Sasano et al., Phys. Rev. Lett. 107, 202501 (2011).
3) L. Stuhl et al., Nucl. Instrum. Methods Phys. Res. A 866,164 (2017).
4) T. Kobayashi et al., Nucl. Instrum. Methods Phys. Res.
B 317, 294 (2013).
5) J. Yasuda et al., Phys. Rev. Lett. 121, 132501 (2018).
6) L. Stuhl et al., Nucl. Instrum. Methods Phys. Res. B 463,
189 (2020).
7) T. Teranishi et al., Phys. Lett. B 407, 110 (1997).
8) R. Raabe et al., Phys. Rev. Lett. 101, 212501 (2008).

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