SciPost Phys. Proc. 3, 004 (2020)

Measurement of spin correlation coefficientsin p–3 He scattering at 65 MeV
Minami Inoue1 , Kimiko Sekiguchi1 , Kenjiro Miki1 , Atomu Watanabe1 , Shinnosuke
Nakai1 , Shun Shibuya1 , Daisuke Sakai1 , Yuta Utsuki1 , Hiroo Umetsu1 , Kichiji
Hatanaka2 , Hiroki Kanda2 , Hooi Jin Ong2 , Tomotsugu Wakasa3 , Syuhei Goto3 , Shinji
Mitsumoto3 , Daiki Inomoto3 , Hina Kasahara3 , Takashi Ino4 , Hideyuki Sakai5 , Yukie
Maeda6 , Kotaro Nonaka6 , Takashi Wakui7 and Masatoshi Itoh8
1 Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan
2 Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan
3 Department of Physics, Kyusyu University, Higashi, Fukuoka 812-8581, Japan
4 High Energy Accelerator Research Organization, Tsukuba, Ibaraki 300-3256, Japan
5 Nishina center, RIKEN, Wako, Saitama 351-0198, Japan
6 Department of Engineering, Miyazaki University, Miyazaki 889-2192, Japan
7 National Institute of Radiological Sciences, Chiba 263-8555, Japan
8 Cyclotron and Radioisotope Center, Tohoku University, Sendai, Miyagi 980-8578, Japan? minami@lambda.phys.tohoku.ac.jp
Proceedings for the 24th edition of European Few Body Conference,Surrey, UK, 2-6 September 2019
doi:10.21468/SciPostPhysProc.3

Abstract
We performed the experiment of p–3 He scattering at 65 MeV by using polarized proton
beams and the newly constructed polarized 3 He target. The proton analyzing power A y ,the 3 He analyzing power ATy , and the spin correlation coefficient C y y were measured.
In the conference, the experimental data were compared with the rigorous numericalcalculations based on various nuclear potentials. Large discrepancies between the experimental data and the calculations were found in the ATy and the Cyy at the backward
angles.
Copyright M. Inoue et al.
This work is licensed under the Creative Commons
Attribution 4.0 International License.
Published by the SciPost Foundation.

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Received 05-11-2019
Accepted 09-01-2020
Check forupdates
Published 24-02-2020
doi:10.21468/SciPostPhysProc.3.004

Introduction

One of the important topics of nuclear physics is to understand the nuclear forces. We especially focus on the three–nuclear force (3N F). 3N Fs appear in systems with more than twonucleons. Importance of 3N Fs has been indicated in various nuclear phenomena, such as few
nucleon scattering [1], binding energies of nuclei [2] and equation of state of nuclear matter [3]. In order to study the dynamical aspects of 3N Fs, such as momentum, spin and isospin
dependencies, a few nucleon scattering system is one attractive probe.
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SciPost Phys. Proc. 3, 004 (2020)

For exploring the properties of 3N Fs, we extensively performed the nucleon–deuteron scattering at intermediate enegies (65–300 MeV/nucleon) [4, 5]. Results of comparison between
the experimental data and the rigorous numerical calculations show clear signatures of 3N Fs
in the cross section. However, the total isospin of N –d scattering system is limited to T =1/2. To investigate the T = 3/2 channel of 3N Fs, we have extended the study to proton–3 He(p–3 He) elastic scattering at intermediate energies. Here we report the measurement of theanalyzing powers (A y and ATy ) and the spin correlation coefficient C y y in p–3 He scattering at
65 MeV.

2Experiments

The experiment was performed at the Research Center for Nuclear Physics (RCNP) cyclotron
facility, Osaka University in Japan. Polarized proton beams were provided by a polarized
ion source and they were transported to the experiment hall. Measurement of p–3 He elastic
scattering was conducted at the ENN course. Schematic view of the experimental setup for
p–3 He elastic scattering is shown in Figure 1. Polarized proton beams bombarded the newly

Figure 1: Schematic view of the experimental setup for p–3 He scattering at the ENN
course, RCNP.

constructed polarized 3 He target [6]. Then, the proton beams were refocused onto a CD2
thin-film target in a beam line polarimeter. Subsequently, they were stopped in the Faraday
cup which was installed in the wall of the ENN course. Typical beam intensities were 10 nA.
Elastically scattered protons from the polarized 3 He target were detected by ∆E–E detectors
which consisted of plastic and NaI(Tl) scintillators. The detectors were placed symmetricallyin left and right directions. Measured angles were θ Lab = 35◦ , 70◦ , 115◦ ( θ C.M. = 47◦ , 89◦ ,133◦ ). During the experiment, the direction of the spin axis for the polarized 3 He target wasflipped and the relative values of the polarization was monitored by the adiabatic fast passageNMR (AFP-NMR) method. The absolute value of the target polarization was calibrated by theelectron paramagnetic resonance (EPR) method [7]. Typical value of the target polarization
was 40 %. The beam polarization was monitored by a beam line polarimeter. The polarimetry
was made by the known analyzing powers in p–d elastic scattering [8]. The CD2 thin-film withthe thickness of 14.8 mg/cm2 was used as a deuterium target. Scattered protons and recoiled
deuterons were detected by plastic scintillators in kinematical coincidence conditions. The004.2

SciPost Phys. Proc. 3, 004 (2020)

typical beam polarizations were p↑y ∼ 50% and p↓y ∼ 20%.

3Results

Figure 2 shows preliminary results of the proton analyzing power A y , the 3 He analyzing power
ATy and the spin correlation coefficient C y y as a function of the scattering angle in the centerof mass system. Open circles show the experimental data. The statistical uncertainties areshown only. Red squares in the figure are the data taken in the different experiment [9]. TheA y data have a good agreement to those measured in Ref. [9]. In the conference, the obtained
data were compared with the calculations based on various nuclear potentials, namely AV18[10], INOY [11], SMS51 [12], SMS53 [12], CD Bonn [13] and CD Bonn+∆ [13], [14]. Thecalculations are not shown here. The A y data had a moderate agreement to the calculations.
Meanwhile, large discrepancies were found in the ATy data and the C y y data at the backward
two angles.

Figure 2: Results of the proton analyzing power A y , the 3 He analyzing power ATy andthe spin correlation coefficient C y y for p–3 He elastic scattering at 65 MeV.

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Summary and Outlook

We have measured p–3 He scattering at 65 MeV by using polarized proton beams and thepolarized 3 He target. Measured angles were θ Lab = 35◦ , 70◦ , 115◦ ( θ C.M. = 47◦ , 89◦ , 133◦ ).
By comparing the experimental data with the rigorous numerical calculations based on various
nucleon potentials, clear discrepancies were found at the backward angles in the 3 He analyzing
power ATy and the spin correlation coefficient C y y . The discrepancies between the data andthe rigorous numerical calculations could be accounted for by 3N Fs.
In order to perform quantitative discussions on 3N F effects in p–3 He elastic scattering,
we are planning the measurement of a complete set of spin correlation coefficients in a wide
angular range.

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SciPost Phys. Proc. 3, 004 (2020)

Acknowledgements
Funding information This work was supported financially in part by the Grants-in-Aid for
Scientific Research No. 25105502, No. 16H02171, and No. 18H05404 of the Ministry of
Education, Culture, Sports, Science, and Technology of Japan.

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