Evaluation Activities at JCPRG

SINGH Jagjit
Meme Media Laboratory, Nuclear Reaction Data Centre, Faculty of Science,
Hokkaido University
DAGVADORJ Ichinkhorloo, EBATA Shuichiro
Nuclear Reaction Data Centre, Faculty of Science, Hokkaido University

Abstract
In this report, we briefly introduce some evaluation activities in Japan ChargedParticle Nuclear Reaction Data Group (JCPRG) in 2016. Evaluation as one of theimportant activity at JCPRG, covers the theoretical investigation of wide range ofnuclear systems close to stability line, at drip-lines and beyond the drip-lines. Theestablished theoretical approaches helps to predict new data which further purposes
the demand for new experiments.

1Introduction

Evaluation of nuclear reaction data is a diligent process of comparison, selection, renormalization
and averaging of the available experimental data, complemented by theoretical calculations. Overthe past few decades, theoretical approaches have encountered various challenges on different fronts
mainly computaional costs. We at JCPRG [1] deals with various theoretical approaches and evaluate nuclear data used for various applications like PET (positron emission therapy) and to improve
the EXFOR database, such as missing data, wrong order of data etc.
This report presents the activities on the evaluation of the nuclear data at JCPRG in 2016.
The report is organized as follows: section 2 describes the nuclear octupole correlation investigatedwith the constraint three-dimensional Skyrme Hartree-Fock+BCS model [2, 3]. Section 3 describes
the analysis of 6,7 Li +n reactions using continuum discretized coupled channel (CDCC) method[4–6]. Section 4 presents the study of continuum excitations in the Borromean systems and theunbound 2n-systems [7–11]. Finally, section 5 presents our conclusions.

2Nuclear octupole correlation investigated with the constraint
three-dimensional Skyrme Hartree-Fock+BCS model

To understand the nuclear deformation and to evaluate theoretically the reaction cross sections
using folding or Glaubeer model, we performed a systematic calculation for the ground state ofover 1000 even-even nuclei. The ground states are prepared with the full self-consistent HartreeFock plus BCS (HF+BCS) method represented in the three-dimensional coordinate space, which
can describe any deformations. A Skyrme effective interaction (SkM∗) is employed and for the- 14 -1.6

1.2220Rn β30220
Rn β31220
Rn β32220
Rn β331.5
1E-Eβ = 0.0 [MeV]

10.8

0.5
03

0.6

3E-Eβ = 0.0 [MeV]2144
Ba β30144
Ba β31
144
Ba β32144
Ba β33

1.4

0.4
0.2

-0.5

0-1
-0.2
-0.4

-1.5
0

0.02

0.04

0.06

0.08
β3m

0.1

0.12

0.14

0.16

00.05

0.1

0.15

0.2

0.25

β3m

Figure 1: Multi-octupole potential energy surfaces for (left) 144 Ba and (right) 220 Rn with respect
to the octupole deformation parameter β3m ; m = 0, 1, 2, 3.
pairing correlation the smoothed pairing constant which is deduced from the level density of thenuclear system, is applied according to same manner in Ref. [2].
The present investigation was able to show the distribution of quadrupole and octupole deformations [3]. We focus on the mass dependence of octupole correlation and evaluate the amplitudeand behaviour of octupole potential energy surface. They are investigated by using the constraint
Skyrme HF+BCS method with the quadratic constraint terms.
Figure 1 shows the potential energy surfaces with respect to the multi-octupole deformation
β3m ; m = 0, 1, 2, 3 which are shown with circle, square, triangle and cross respectively, for 144 Ba
in the left and for 220 Rn in the right. 144 Ba is one of the lighter octupole deformed nuclei which
has Z = 56 and N = 88. It has a local minimum on the only β30 (pear shape) potential energy
surface. The amplitude of correlation might be estimated as about 200 keV. 220 Rn is one of theheavier octupole deformed nuclei which has Z = 86 and N = 134. The local minimum appears in
the not only β30 but also β31 (banana shape) and β32 (tetrahedral shape) potential energy surfaces.
The amplitude of β30 octupole correlation might be about 1.5 MeV which is much larger than
144 Ba. Furthermore, the 220 Rn results indicate it has the excitation states with different ocutpole
deformation. They will be useful knowledge for the isomers of heavier octupole deformed nuclei.
The study will be extended to not only nuclear structure but also nuclear reaction. We will
construct a theoretical database based on these results for not only ground states but also reaction
cross sections etc. The theoretical database will be able to correct the EXFOR database, such as
missing data, wrong order of data and strange angler distribution.

3

Analysis of 6,7 Li +n reactions using CDCC method

In this fiscal year, we extend the CDCC [12] analysis of the integrated elastic and inelastic scattering cross sections of n+Li with incident neutron energies below 14.1 MeV using the JLM (J.-P.
Jeukenne, A. Lejeune, and C. Mahaux) which was proposed for an energy region lower than 10 MeV[13]. This is because of the fact that the various parameter sets are defined for the JLM effective
nucleon-nucleon interaction in the different energy regions [13, 14]. Furthermore, we employ thenormalization factors to adjust folding potentials of the JLM for the n+ 6,7 Li elastic scattering in asimilar way as the previous studies [4, 5, 15]. The energy-dependent normalization factors λv andλw for real and imaginary parts, respectively, of the n− 6,7 Li folding potentials are determined fromthe integrated elastic cross section data. Using the obtained normalization factors, we calculate
the inelastic scattering cross sections and angular distributions and compare the results with the- 15 -JLM−1JLM−2

JENDL−3.3
R.Batchelor (1963)
F.Merchez (1966)
J.A.Cookson (1967)
J.C.Hopkins (1968)
H.H.Hogue (1979)
P.W.Lisowski (1980)
S.Chiba (1985)
M.Adel−Fawzy (1987)
G.Chen (2009)

100

100246810121416

18

2022

JENDL−3.3
R.Batchelor (1963)
F.Merchez (1966)J.A.Cookson (1967)
J.C.Hopkins (1968)
H.H.Hogue (1979)
P.W.Lisowski (1980)
S.Chiba (1985)
M.Adel−Fawzy (1987)
M.Ibaraki (1998)
G.Chen (2009)

0Scattering Cross Section [barn]

Scattering Cross Section [barn]

JLM−1
JLM−2

−1

10

24

2

4

68

10

12

14

16

18

20

2224

Incident neutron energy [MeV]

Incident neutron energy [MeV]

Figure 2: The integrated (left) elastic cross sections of the n+ 6 Li scattering, (Right) inelastic n+
6 Li scattering cross sections, for the excited 3+ state at the excitation energy of 2.18 MeV of 6 Liin comparison with the evaluated data and experimental data.
experimental data without any additional parameters. The calculated results [6] are presented inFigure 2. The CDCC calculation gives a satisfactorily good agreement with the experimental data.
We also purpose to extend the CDCC analysis of the scattering cross section of 16 O target withincident proton.First, we investigated the elastic scattering cross section of 16 O +p reactions with
15 N +p cluster model. The current calculated results of elastic scattering cross section data areshown to reproduce the observed data. The next purpose of our work is to calculate 16 O(p, pn)
15 O positron source, detailed information on the energy spectrum, angular distribution and production cross section. This kind of research is applicable to the PET (positron emission therapy)
and nuclear reaction data fields.

4Continuum excitations in the Borromean systems and the unbound 2n-systems

In recent years, there has been rapidly increasing interest in the study of the Borromean nuclei
sitting right on the top of neutron drip-lines and two-neutron decays of unbound systems beyond
the neutron drip-line. This study demands a three-body description with proper treatment ofcontinuum, whereas the conventional shell-model assumptions are being insufficient. Recently wehave developed a simple nuclear structure model for ground and continuum states of the Borromean
nuclei [7–11]. Initially it is tested for 6 He, the states of which are built by starting from thecontinuum single-particle spd-states of 5 He. The role of different continuum components in theweakly bound nucleus 6 He is studied by coupling unbound spd-waves of 5 He by using simple
pairing contact-delta interaction. Our results show that the 6 He ground state 0+ displays collective
nature by taking contribution from five different oscillating continuum states,that are summed
up to give an exponentially decaying bound wavefunction. In summary, the electric multipole
response of 6 He has been investigated by using a simple structure model and the role of different
configurations has been explored in each case. Fig. (3), shows our predictions for the response of
6 He to electromagnetic excitations of different multipolarity by showing the centroid of each state
and the width on horizontal scale. We expect that our efforts might be of help to unravel the- 16 -

6+

Heg.s (0 )+01+23

J

3

1.18

20.76

1

10.16

2.91

( 5.27 )010.66

1.25

0

10

515

EC (MeV)Figure 3: Schematic representation of the spectrum of 6 He predicted by our simple model. The
parenthesis in the J = 1− response indicates the uncertainty on the position of the peak. The lines
correspond to the widths [11].
complex patterns seen in the continuum spectrum of 6 He.
Recently in 2016 a high precision interaction cross section (σI ) for 22 C, was measured on a carbon
target at 235 MeV/nucleon at RIKEN [16]. This higher-precision measurement is the motivationof selecting the 2n− halo 22 C, for extending our study in this fiscal year. We have also planned thepossibility of extension of our simple model from Borromean systems to the two-neutron unboundsystems beyond the neutron drip-line i.e. 26 O [17]. This study will help to unravel the complex
patterns seen in the continuum spectrum of these systems and assigning spin and parity to newly
measured low lying excited states.

5Summary

In summary, we have investigated the amplitude of octupole correlation in 144 Ba and 220 Rn
for multi-octupole deformation with the constraint three-dimensional Skyrme Hartree-Fock+BCSmodel. For the study of 6,7 Li +n reactions, by introducing normalization factors using CDCC,
the calculated elastic and inelastic scattering cross sections gives a satisfactorily good agreementwith the experimental data. For study of Borromean systems and the unbound 2n-systems, theelectric multipole response of 6 He has been investigated by using a simple structure model and therole of different configurations has been explored in each case. These theoretical approaches arestill in progress to implement the possible extensions discussed in the text to provide further new
information on nuclear structure and nuclear reactions in near future.

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Acknowledgment
This work was funded by ImPACT Program of Council for Science, Technology and Innovation(Cabinet Office, Government of Japan), and was supported by Interdisciplinary Computational
Science Program in CCS, University of Tsukuba.

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