Transcript Breakup reactions

Breakup of halo nuclei with Coulomb-corrected
eikonal method
Y. Suzuki (Niigata)
1.
2.
3.
4.
Motivation for breakup reactions
Eikonal and adiabatic approximations
Coulomb-corrected eikonal model
Application to 2n halo nuclei
Collaborators:
B. Abu-Ibrahim (Cairo)
P. Capel, D. Baye, P. Descouvemont (ULB)
PTP112 (2004), PTP114(2005), PRC78(2008), PRC submitted
RCNP.08
1. Motivation
・Breakup reactions are important to study halo nuclei which are
characterized by weakly bound, short-lived, few-cluster structure
・E1 strength, NN correlation are deduced from breakup cross sections
FSI, breakup into continuum
・Sound reaction theory is needed to extract structure information
Perturbation expansion, Adiabatic approximation,
Eikonal approximation, CDCC, …
Information on B(E1) distribution
First-order perturbation theory
for Coulomb breakup
Contribution of other multipoles to
breakup cross sections?
New 2n correlation experiment (Nakamura et al.)
Taken from K. Hagino
2. Eikonal and adiabatic approximations
--- Case of one-neutron halo nucleus ---
Projectile
Eikonal approximation
f
C
Target
DEA (Dynamical Eikonal Approximation)
Adiabatic approx.
Test of DEA
11
Be+208Pb at 69 MeV/nucleon
Angle-integrated cross sections as a function of
the relative energy of n-10Be fragments
G. Goldstein et al. PRC73 (2006)
N. Fukuda et al. PRC70 (2004)
Test of eikonal and adiabatic approximations
--- Breakup effect in elastic scattering of 6He on 12C --V. Lapoux et al. PRC66 (2002)
40 MeV/nucleon
B. Abu-Ibrahim & Y.S. NPA728 (2003)
Folding
Full
Eikonal approx.:
N-12C optical potential
VMC w.f. for 6He
Glauber model:
3α microscopic cluster
model w.f. for 12C
NN profile function
α+ n + n three-body model for 6He
CDCC
T. Matsumoto et al. PRC70 (2004)
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3. Coulomb-corrected eikonal
Rutherford scattering
Long-ranged breakup effect (adiabatic approx. breaks down)
Logarithmic divergence
Coulomb-corrected eikonal phase (CCE)
J. Margueron et al. NPA703 (2002)
Test of CCE
Breakup of 11Be (one-neutron halo nucleus) on Pb
ＰＴＰ 112 (2004)
CCE vs DEA
b-dep. of elastic breakup probability
11Be on 208Pb at 69 MeV/nucleon
4. Application to breakup of two-neutron halo nucleus
Challenging four-body problem including continuum final states
・Expensive computation time
・Final-state interaction
・Extraction of E1 strength function or effects of other multipoles
Case study:
6He
breakup on 208Pb at 70, 240 MeV/A
・Reaction dynamics is fully taken into account in CCE model
・ 6He is described with α+ n + n three-body model
・Bound and continuum states of 6He are described with HHE
PRC submitted
RCNP.08
6He
breakup on 208Pb at 70 MeV/A
--- Contribution of partial cross sections --Cross sections are directly measurable.
Determining E1 strengths relies on model assumptions
(e.g. 1- dominance, elimination of nuclear effects).
Dotted lines denote final plane waves
Comparison with solid lines denotes the
importance of FSI.
J=0,2 contributions: 10% at low energies, 35% at E=5MeV
--- Double differential cross sections from 1- component --information on correlations
1
Core
2
The peak corresponds to the broad 1- resonance.
6He
breakup on 208Pb at 240 MeV/A
No convolution
Dashed, dotted denote 1- partial cross sections
T. Aumann et al. PRC59 (1999)
E1 strength distribution of 6He
Myo et al. PRC63 (2001)
Summary
・A correction is introduced to avoid the divergence due
to the Coulomb interaction in the eikonal model.
・The CCE is accurate enough to take into account the
reaction dynamics, making it possible to reconstruct the
properties of two- and three-body projectile wave functions.
・Bound and continuum states of three-body system are
described in HH basis with full account of final state interactions.
・Various cross sections, in particular including multi-differential
cross sections can be calculated.
・The contribution of various multipole transitions is quantified.
・The CCE is applied to 6He+208Pb at 70 and 240 MeV/nucleon.
The results disagree with the 240 MeV data.
B(E1) strength? Further new data are desirable.
RCNP.08