Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 47 (2014)

Deuteron Analyzing Powers for dp elastic scattering at 250–294
MeV/nucleon and three-nucleon force
K. Sekiguchi,∗1 Y. Wada,∗1 J. Miyazaki,∗1 T. Taguchi,∗1 U. Gebauer,∗1 M. Dozono,∗2 S. Kawase,∗3
Y. Kubota,∗3 Y. Maeda,∗4 T. Mashiko,∗1 K. Miki,∗5 S. Sakaguchi,∗6 H. Sakai,∗2 N. Sakamoto,∗2
M. Sasano,∗2 Y. Shimizu,∗2 K. Takahashi,∗1 R. Tang,∗2 T. Uesaka,∗2 T. Wakasa,∗6 and K. Yako∗3
potentials, namely CDBonn3) , AV184) , Nijmegen I,and Nijmegen II5) . The solid lines are the calculations including Urbana IX 3NF6) based on the AV18
potential.
The tensor analyzing power T22 reveals an energy
dependence diﬀerent from those obtained for the crosssection and the other analyzing powers iT11 , T20 , andT21 1) . At 135 MeV/N and below, adding 3NFs degrades the description of data in a large angular region.
It is contrary to what happens at energies above 250
MeV/N, for which large 3NF eﬀects are supported bythe T22 data.

The study of three-nucleon forces (3NFs) is essential for clarifying various nuclear phenomena. In addition to the ﬁrst signals indicating 3NF eﬀects in thebinding energies of 3 H and 3 He, the signiﬁcance of
3NFs has been recently pointed out for descriptionsof discrete states in higher-mass nuclei. Three-nucleon
scattering at intermediate energies (E/A ∼ 200 MeV)
is one attractive approach to investigate the dynamical aspects of 3NFs, such as momentum and/or spin
dependences. With the aim of clarifying the roles of
the 3NFs in nuclei, experimental programs with polarized deuteron beams at intermediate energies are inprogress at RIBF. As the ﬁrst step, we measured acomplete set of deuteron analyzing powers (iT11 , T20 ,T21 , T22 ) in deuteron–proton (dp) elastic scattering at
250 and 294 MeV/nucleon (MeV/N).
A schematic diagram of the experimental setup canbe found in Ref. (1). Vector- and tensor-polarized
deuteron beams were accelerated by the injector cyclotrons AVF and RRC up to 90 (100) MeV/N; subsequently, they were accelerated up to 250 (294) MeV/Nby the SRC. Typical values of the beam polarizations
were 80% of the theoretical maximum values. The
measurement for dp elastic scattering was performedby using a detector system, BigDpol, installed at theextraction beamline of the SRC. Polyethylene (CH2 )of thickness 330 mg/cm2 was used as the hydrogentarget. In BigDpol, four pairs of plastic scintillators
coupled with photo-multiplier tubes were placed symmetrically in the azimuthal directions to the left, right,
up and down. Scattered deuterons and recoil protons
were detected in the kinematical coincidence conditionby each pair of detectors. The angles (θc.m. ) measured
in the center-of-mass system are in the range 40◦ –162◦ .
In the experiment, the deuteron beams were stopped
in a Faraday cup, which was installed at the focal plane
F0 of the BigRIPS spectrometer.
Here, we report the results of energy dependence ofthe deuteron tensor analyzing power T22 . The angular distribution of T22 is shown with open circles, together with the previously reported data at 70 and
135 MeV/N1) . The red (blue) bands in the ﬁgure
are the Faddeev calculations with (without) Tucson–Melbourne’99 (TM99) 3NF2) based on the modern NN
∗1
∗2
∗3
∗4
∗5
∗6In order to obtain a consistent understanding of thespin dependence of 3NFs up to high momenta, we planto perform deuteron analyzing power measurements at190 MeV/N.

Fig. 1. Tensor analyzing power T22 for dp elastic scattering
at 70–294 MeV/N.

References
1) K. Sekiguchi et al.: Phys. Rev. C 83, 061001 (2011).
2) S. A. Coon and H. K. Han: Few Body Syst. 30, 131(2001).
3) R. Machleidt: Phys. Rev. C 63, 024001 (2001).
4) R. B. Wiringa et al.: Phys. Rev. C 51, 38 (1995).
5) V. G. J. Stoks et al.: Phys. Rev. C 49, 2950 (1994).
6) B. S. Pudliner et al.: Phys. Rev. C 56, 1720 (1997).

Department of Physics, Tohoku University
RIKEN Nishina Center
CNS, University of Tokyo
Faculty of Engineering, University of Miyazaki
RCNP, Osaka University
Department of Physics, Kyushu University- 14 -