559 research outputs found
Multipole Expansion for Relativistic Coulomb Excitation
We derive a general expression for the multipole expansion of the
electro-magnetic interaction in relativistic heavy-ion collisions, which can be
employed in higher-order dynamical calculations of Coulomb excitation. The
interaction has diagonal as well as off-diagonal multipole components,
associated with the intrinsic and relative coordinates of projectile and
target. A simple truncation in the off-diagonal components gives excellent
results in first-order perturbation theory for distant collisions and for beam
energies up to 200 MeV/nucleon.Comment: 3 figures, Accepted for publication in Phys. Rev.
Recent developments in the eikonal description of the breakup of exotic nuclei
The study of exotic nuclear structures, such as halo nuclei, is usually
performed through nuclear reactions. An accurate reaction model coupled to a
realistic description of the projectile is needed to correctly interpret
experimental data. In this contribution, we briefly summarise the assumptions
made within the modelling of reactions involving halo nuclei. We describe
briefly the Continuum-Discretised Coupled Channel method (CDCC) and the
Dynamical Eikonal Approximation (DEA) in particular and present a comparison
between them for the breakup of 15C on Pb at 68AMeV. We show the problem faced
by the models based on the eikonal approximation at low energy and detail a
correction that enables their extension down to lower beam energies. A new
reaction observable is also presented. It consists of the ratio between angular
distributions for two different processes, such as elastic scattering and
breakup. This ratio is completely independent of the reaction mechanism and
hence is more sensitive to the projectile structure than usual reaction
observables, which makes it a very powerful tool to study exotic structures far
from stability.Comment: Contribution to the proceedings of the XXI International School on
Nuclear Physics and Applications & the International Symposium on Exotic
Nuclei, dedicated to the 60th Anniversary of the JINR (Dubna) (Varna,
Bulgaria, 6-12 September 2015), 7 pages, 4 figure
Time-dependent wave-packet approach for fusion reactions of halo nuclei
The fusion reaction of a halo nucleus 11Be on 208Pb is described by a
three-body direct reaction model. A time-dependent wave packet approach is
applied to a three-body reaction problem. The wave packet approach enables us
to obtain scattering solutions without considering the three-body scattering
boundary conditions. The time evolution of the wave packet also helps us to
obtain intuitive understanding of the reaction dynamics. The calculations
indicate a decrease of the fusion probability by the presence of the halo
neutron.Comment: 7 pages, 3 figures, use espcrc1.sty, Talk at the International
Symposium on "Physics of Unstable Nuclei (ISPUN02)", Halong Bay, Vietnam,
November 20-25, 200
3-D unrestricted TDHF fusion calculations using the full Skyrme interaction
We present a study of fusion cross sections using a new generation
Time-Dependent Hartree-Fock (TDHF) code which contains no approximations
regarding collision geometry and uses the full Skyrme interaction, including
all of the time-odd terms. In addition, the code uses the Basis-Spline
collocation method for improved numerical accuracy. A comparative study of
fusion cross sections for is made with the older TDHF
results and experiments. We present results using the modern Skyrme forces and
discuss the influence of the new terms present in the interaction.Comment: 7 pages, 10 figure
S17(0) Determined from the Coulomb Breakup of 83 MeV/nucleon 8B
A kinematically complete measurement was made of the Coulomb dissociation of
8B nuclei on a Pb target at 83 MeV/nucleon. The cross section was measured at
low relative energies in order to infer the astrophysical S factor for the
7Be(p,gamma)8B reaction. A first-order perturbation theory analysis of the
reaction dynamics including E1, E2, and M1 transitions was employed to extract
the E1 strength relevant to neutrino-producing reactions in the solar interior.
By fitting the measured cross section from Erel = 130 keV to 400 keV, we find
S17(0) = 17.8 (+1.4, -1.2) eV b
Region of hadron-quark mixed phase in hybrid stars
Hadron--quark mixed phase is expected in a wide region of the inner structure
of hybrid stars. However, we show that the hadron--quark mixed phase should be
restricted to a narrower region to because of the charge screening effect. The
narrow region of the mixed phase seems to explain physical phenomena of neutron
stars such as the strong magnetic field and glitch phenomena, and it would give
a new cooling curve for the neutron star.Comment: to be published in Physical Review
Many-body approach to the nonlinear interaction of charged particles with an interacting free electron gas
We report various many-body theoretical approaches to the nonlinear decay
rate and energy loss of charged particles moving in an interacting free
electron gas. These include perturbative formulations of the scattering matrix,
the self-energy, and the induced electron density. Explicit expressions for
these quantities are obtained, with inclusion of exchange and correlation
effects.Comment: 11 pages, 5 figures. To appear in Journal of Physics
Coulomb-nuclear interference in the breakup of Be
Within a theory of breakup reactions formulated in the framework of the post
form distorted wave Born approximation, we calculate contributions of the pure
Coulomb and the pure nuclear breakup as well as those of their interference
terms to a variety of cross sections in breakup reactions of the one-neutron
halo nucleus Be on a number of target nuclei. In contrast to the
assumption often made, the Coulomb-nuclear interference terms are found to be
non-negligible in case of exclusive cross sections of the fragments emitted in
this reaction on medium mass and heavy target nuclei. The consideration of the
nuclear breakup leads to a better description of such data.Comment: 9 pages, latex, 2 figures, to be published in Phys. Rev. C (Rapid
Communication
Calculations of three-body observables in ^8B breakup
We discuss calculations of three-body observables for the breakup of ^8B on a
^{58}Ni target at low energy using the coupled discretised continuum channels
approach. Calculations of both the angular distribution of the ^7Be fragments
and their energy distributions are compared with those measured at several
laboratory angles. In these observables there is interference between the
breakup amplitudes from different spin-parity excitations of the projectile.
The resulting angle and the energy distributions reveal the importance of the
higher-order continuum state couplings for an understanding of the
measurements.Comment: 22 pages (postscript), accepted in Phys. Rev.
Decay Rate of Triaxially-Deformed Proton Emitters
The decay rate of a triaxially-deformed proton emitter is calculated in a
particle-rotor model, which is based on a deformed Woods-Saxon potential and
includes a deformed spin-orbit interaction. The wave function of the
ground state of the deformed proton emitter Ho is obtained
in the adiabatic limit, and a Green's function technique is used to calculate
the decay rate and branching ratio to the first excited 2 state of the
daughter nucleus. Only for values of the triaxial angle
is good agreement obtained for both the total decay rate and the 2
branching ratio.Comment: 19 pages, 4 figure
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