Future plan to study light nuclei near the neutron drip line viacharge-exchange (p,n) reactions in inverse kinematics

L. Stuhl,∗1 M. Sasano,∗1 D. Ahn,∗1 H. Baba,∗1 W. Chao,∗2 M. Csatlos,∗3 Zs. Dombradi,∗3 M. Dozono,∗4

N. Fukuda,∗1 B. Hong,∗5 N. Inabe,∗1 T. Isobe,∗1 G. Jhang,∗5 M. Kaneko,∗6 S. Kawase,∗4 K. Kisamori,∗4

M. Kobayashi,∗4 N. Kobayashi,∗7 T. Kobayashi,∗8 Y. Kondo,∗9 Z. Korkulu,∗1 S. Koyama,∗7 A. Krasznahorkay,∗3

T. Kubo,∗1 Y. Kubota,∗1,∗4 C. S. Lee,∗1,∗4 Y. Matsuda,∗10 S. Michimasa,∗4 E. Milman,∗11 T. Motobayashi,∗1

T. Murakami,∗6 S. Naimi,∗1 T. Nakamura,∗9 N. Nakatsuka,∗6 M. Niikura,∗7 M. Kurata-Nishimura,∗1

A. Ohkura,∗12 S. Ota,∗4 H. Otsu,∗1 V. Panin,∗1 S. Reichert∗13 S. Sakaguchi,∗12 H. Sakai,∗1 M. Sako,∗1

H. Sakurai,∗7 H. Sato,∗1 Y. Satou,∗14 M. Shikata,∗9 Y. Shimizu,∗1 S. Shimoura,∗4 Y. Shindo,∗12 H. Suzuki,∗1

M. Tabata,∗12 M. Takaki,∗4 H. Takeda,∗1 J. Timar,∗3 Y. Togano,∗9 H. Tokieda,∗4 J. Tsubota,∗9 T. Uesaka,∗1

Zs. Vajta,∗3 T. Wakasa,∗12 K. Yako,∗4 J. Yasuda,∗12 K. Yoneda∗1 and J. Zenihiro∗1

We plan to investigate the isovector response of11Li and 14Be nuclei near the neutron drip line.The variation of spin-isospin residual interaction andthe effect of spatial distribution of neutron skin orhalo on spin-isospin responses will be studied usingcharge-exchange (p,n) reactions, at intermediate en-ergies (260-280 MeV/nucleon) in inverse kinematics.The Gamow-Teller (GT) and spin-dipole (SD) tran-sitions including their giant resonances will be mea-sured. Experimentally, the (p,n) reactions at interme-diate beam energies can selectively excite GT states upto high excitation energies in the final nucleus. Thereis a close proportionality between the cross-sections at0◦ and the transition strengths B(GT) in these reac-tions1). Therefore, the (p,n) reactions provide a pow-erful method to study the B(GT) distributions.An experimental approach to study the variation of

the spin-isospin collectivity is the energy difference be-tween the GT giant resonance (GTGR) and isobaricanalog state (IAS) over a wide range of (N-Z)/A. Mea-surements on stable nuclei show that the GTGR is afew MeV higher than the IAS. This difference gives ac-cess to spin-isospin residual interaction strength. How-ever, it is expected to differ at high (N-Z)/A2,3). Ac-cording to predictions for (N-Z)/A values greater than0.3, the GTGR energy decreases below the IAS energy.It is a compelling interest to obtain new experimentaldata on nuclei with high (N-Z)/A along the neutrondrip line to clarify how the spin-isospin residual inter-action strength changes and whether it is related alsoto the skin or halo structures. With only two pioneer

∗1 RIKEN Nishina Center∗2 School of Physics, Peking University∗3 MTA Atomki, Debrecen, Hungary∗4 CNS, University of Tokyo∗5 Department of Physics, Korea University∗6 Division of Physics and Astronomy, Kyoto University∗7 Department of Physics, University of Tokyo∗8 Department of Physics, Tohoku University∗9 Department of Physics, Tokyo Institute of Technology∗10 Department of Physics, Konan University∗11 Department of Physics, Kyungpook National University∗12 Department of Physics, Kyushu University∗13 Department of Physics, Technical University Munich∗14 Dept. of Physics and Astronomy, Seoul National University

experiments4,5) this effect is not well studied and fur-ther experimental data are needed.

A new experimental technique developed at NSCL,MSU6,7) will be applied to measure the (p,n) reactionin inverse kinematics which enables us to achieve a highluminosity using a thick target without losing the in-formation on the recoil neutron momentum necessaryfor the missing mass reconstruction. The setup us-ing BigRIPS, WINDS (Wide-angle Inverse-kinematicsNeutron Detectors for SHARAQ) and the SAMURAIspectrometer together with a 10-mm thick liquid hy-drogen target will allow us to extract the GT and SDtransition strengths from the low-lying region up to 40MeV excitation energies. The use of the SAMURAI iscrucial for covering all decay channels simultaneouslyand for obtaining conclusive data on the GT strengthsof the nuclei of interest.

By using WINDS placed at a distance of 1 m (1.25m) from the target position both on left and right (topand bottom) sides with respect to the beam line, wedetect recoil neutrons from the (p,n) reaction. Fromthe measured neutron TOF and recoil angle, the exci-tation energy and center-of-mass scattering angle canbe deduced. The reaction products will be momentum-analyzed by the SAMURAI spectrometer. The parti-cle identification for the reaction residues will be madeusing the TOF and energy loss information measuredby hodoscopes (HODF, HODP). The energy loss in-formation will be complementary used. The NEBULAdetector will be used for tagging the neutron decay ofthe reaction products.

Our proposal has been presented at the 15th Pro-gram Advisory Committee for Nuclear Physics exper-iments at RI Beam Factory (NP-PAC). The NP-PACapproved 5 days of beam time.

References1) T. D. Taddeucci et al.: Nucl. Phys. A 469, 125 (1987).2) C. Gaarde: Nucl. Phys. A 396, 127 (1983).3) H. Sagawa et al.: Phys. Lett. B 303 215 (1993).4) M. Kobayashi et al.: JPS Conf. Proc. 1, 013034 (2014).5) H. Sakai et al.: In preparation.6) M. Sasano et al.: Phys. Rev. Lett. 107, 202501 (2011).7) M. Sasano et al.: Phys. Rev. C 86, 034324 (2012).

Spin-dipole response of 4He by using (8He, 8Li(1+))

H. Miya,∗1 S. Shimoura,∗1 K. Kisamori,∗1,∗2 M. Assie,∗3 H. Baba,∗2 T. Baba,∗4 D. Beaumel,∗3 M. Dozono,∗1

T. Fujii,∗2 N. Fukuda,∗2 S. Go,∗1 F. Hammache,∗3 E. Ideguchi,∗5 N. Inabe,∗2 M. Itoh,∗6 D. Kameda,∗2

S. Kawase,∗1 T. Kawabata,∗4 M. Kobayashi,∗1 Y. Kondo,∗7 T. Kubo,∗2 Y. Kubota,∗1,∗2 C. S. Lee,∗1,∗2

Y. Maeda,∗8 H. Matsubara,∗9 S. Michimasa,∗1 K. Miki,∗5 T. Nishi,∗10 M. Kurata-Nishimura,∗2 S. Ota,∗1

H. Sakai,∗2 S. Sakaguchi,∗11 M. Sasano,∗2 H. Sato,∗2 Y. Shimizu,∗2 H. Suzuki,∗2 A. Stolz,∗12 M. Takaki,∗1

H. Takeda,∗2 S. Takeuchi,∗2 A. Tamii,∗5 H. Tokieda,∗1 M. Tsumura,∗4 T. Uesaka,∗2 K. Yako,∗1 Y. Yanagisawa∗2

and R. Yokoyama∗1

The spin dipole (SD) (∆ S = ∆ L =1) of spin-isospinresponses is connected with the tensor correlation innuclei. Especially, on a double-closed nucleus, the SDexcitation contribution is large because of the nucleonconfiguration. The SD excitation function was mea-sured on 4He which is the lightest double-closed nu-cleus. This is important for the study of supernovanucleosynthesis with the neutrino-nucleus reaction1).

We coducted the exothermic charge-exchange (CE)reaction of 4He(8He, 8Li(1+))4H. CE reactions arepowerful tools to study the spin-isospin responses.The spin-flip transition of 8He(0+) → 8Li(1+) canbe identified by measuring the de-excited γ-rays(Eγ=0.98 MeV) from the first 1+ state of 8Li. Thebeam energy region of 100–300 MeV/nucleon is suit-able for the study of the spin-isospin responses2).

The experiment was performed at the RIKENRIBF facility by using BigRIPS3), the high-Resolutionbeamline4), and the SHARAQ spectrometer5). The8He beam, which was produced via a projectile-fragmentation reaction with an 18O beam and 9Betarget, was transported to the secondary target po-sition at an intensity of 2 MHz. We used the liquid-4He target6) with a thickness of 120 mg/cm2. In or-der to determine the excitation energy using missingmass method, the momenta of 8He and 8Li at an en-ergy of 190 MeV/nucleon were measured at the beam-line and SHARAQ within the low-pressure multi-wiredrift chamber (LP-MWDC) 7) and cathode readoutdrift 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(8He,8Li) reaction (black line). The contribution ofboth the 4He target and hydrogen is included in this

∗1 Center for Nuclear Study, The University of Tokyo∗2 RIKEN Nishina Center∗3 Institut de Physique Nucleaire, 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

Excitation energy [MeV]-30 -20 -10 0 10 20 30 40 50 60 70

Cou

nts/

2 M

eV

0

5

10

15

20

25

30

Fig. 1. Excitation energy distribution of 4H obtained us-

ing missing mass method. The red line shows the back-

ground estimated from the contamination of the exci-

tation energy distribution.

spectrum. The region around 10 MeV and −17 MeVshows the 4He →4 H and 1H → n reactions, respec-tively. The 1H → n reaction originates at the plasticscintilator installed at the upstream of the target. Theamount of contamination (red line) was estimated byusing the energy loss of the LP-MWDC placed betweenthe scintilator and the target. Thus, the 4He(8He,8Li)4H reaction was obtained.

Further analysis to obtain the angular distributionand double differential cross-sections is now in progressto obtain the isovector SD strength of 4He.

References1) 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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Ⅱ-1. Nuclear Physics RIKEN Accel. Prog. Rep. 48 (2015)RIKEN Accel. Prog. Rep. 48 (2015) Ⅱ-1. Nuclear Physics

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