Transcript スライド 1 - Surrey

Analyses for four-body breakup
reactions of 6He
Takuma Matsumoto
(RIKEN Nishina Center)
T. Egami1, K. Ogata1, Y. Iseri2,
M. Yahiro1 and M. Kamimura1
(1Kyushu University, 2Chiba-Keizai College)
50th Anniversary Symposium on Nuclear Sizes and Shapes
23 June – 25 June, 2008
Introduction
 The unstable nuclear structure can be efficiently
investigated via the breakup reactions.
Nuclear and Coulomb
 Elastic cross section
 Breakup cross section
 Momentum distribution
of emitted particles
Unstable Nuclei
Target
Structure information
 An accurate method of treating breakup processes
is needed.
Region of Interest
 In a simplified picture, light neutron rich nuclei can
be described by a three-body model
11C
12C
13C
14C
15C
16C
8B
10B
11B
12B
13B
14B
15B
7Be
9Be 10Be 11Be 12Be
9C
6Li
3He 4He
p
2H
10C
7Li
6He
8Li
9Li
8He
3H
n
n
n
S2n < 1 MeV
17C
18C
17B
20C
19B
14Be
11Li
ne
i
l
rip
d
ron
t
u
Ne
1
2
Four-Body Breakup
3
core
n + n + core
19C
4
Continuum-Discretized Coupled-Channels
 The Continuum-Discretized Coupled-Channels method (CDCC)
 Developed by Kyushu group about 20 years ago
M. Kamimura, M. Kawai, et al., PTP Suppl. 89, 1 (1986)
 Fully-quantum mechanical method
Four-body
breakup reactions
 Successful for nuclear and Coulomb breakup reactions
 Essence of CDCC
Continuum
discretization
Discretized
states
Three-body breakup
continuum
Breakup continuum states
are described by a finite
number of discretized states
 A set of eigenstates forms a
Breakup threshold
complete set within a finite
model space that is
Bound
important
for breakup
We have to calculate three-body discretized
continuum
states
processes
Ground and Breakup States of 6He
 Gaussian Expansion Method : E. Hiyama et al., Prog. Part. Nucl. Phys. 51, 223
Excitation energy of 6He [MeV]
 An accurate method of solving few-body problems. Ip=0+
 A variational method with Gaussian basis functions
 Take all the sets of Jacobi coordinates
Ip=1-
Ip=2+
 6He : n + n + 4He (three-body model)
n
n
4He
Channel 1
n
n
n
4He
Channel 2
n
4He
Channel 3
 Hamiltonian
 Vnn : Bonn-A
 Van : KKNN int.
6He+12C, 6He+209Bi
6He+12C
Scattering
6He+209Bi
scattering
scattering
n
n
n
n
4He
4He
6He
6He
12C
Breakup: Nuclear
Breakup channel : 0+, 2+
Coupling potential : Double folding
with DDM3Y
209Bi
Breakup: Nuclear and Coulomb
Breakup channel : 0+, 1-, 2+
Coupling potential : Cluster Folding
Nuclear Breakup Reactions of 6He on 12C
 E >> Coulomb barrier :
Negligible of Coulomb breakup effects
 Elastic cross section
Nuclear and Coulomb Breakup of 6He on 209Bi
 E ~ Coulomb barrier :
Coulomb breakup effects are to be significant
 Elastic cross section
THO-CDCC calculation : M. Rodriguez-Gallardo et al., arXiv:0710.0769v2
Breakup Cross Section
resonance
Nuclear and Coulomb Breakup
g.s → 0+ cont.
s BU [mb]
s BU [mb]
Nuclear Breakup
6He+12C @ 229.8 MeV
g.s → 1- cont.
g.s → 2+ cont.
enna [MeV]
Discrete S matrix
enna [MeV]
Continuum S matrix
E1 Transition Strength : B(E1)
 Discretized B(E1) strength
 Smoothing procedure
Ip = 1 -
ground state
Calculated by T. Egami (Kyushu University)
Summary
 We propose a fully quantum mechanical method called four-body
CDCC, which can describe four-body nuclear and Coulomb breakup
reactions.
 We applied four-body CDCC to analyses of 6He nuclear and
Coulomb breakup reactions, and found that four-body CDCC can
reproduce the experimental data.
 Four-body CDCC is indispensable to analyse various four-body
breakup reactions in which both nuclear and Coulomb breakup
processes are to be significant
 In the future work, we are developing a new method of calculation
of energy distribution of breakup cross section and momentum
distribution of emitted particle.