1,988 research outputs found
Coulomb breakup effects on the elastic cross section of He+Bi scattering near Coulomb barrier energies
We accurately analyze the He+Bi scattering at 19 and 22.5 MeV
near the Coulomb barrier energy, using the continuum-discretized
coupled-channels method (CDCC) based on the ++He+Bi four-body
model.
The three-body breakup continuum of He is discretized by diagonalizing
the internal Hamiltonian of He in a space spanned by the Gaussian basis
functions.
The calculated elastic and total reaction cross sections are in good
agreement with the experimental data, while the CDCC calculation based on the
di-neutron model of He, i.e., the +He+Bi three-body
model, does not reproduce the data.Comment: 5 pages, 5 figures, uses REVTeX 4, submitted to Phys. Rev.
Determination of S17 from 8B breakup by means of the method of continuum-discretized coupled-channels
The astrophysical factor for 7Be(p,\gamma)8B at zero energy, S17(0), is
determined from an analysis of 208Pb(8B, p+7Be)208Pb at 52 MeV/nucleon by means
of the method of continuum-discretized coupled-channels (CDCC) taking account
of all nuclear and Coulomb breakup processes. The asymptotic normalization
coefficient (ANC) method is used to extract S17(0) from the calculated
breakup-cross-section. The main result of the present paper is S17(0)=20.9
+2.0/-1.9 eV b. The error consists of 8.4% experimental systematic error and
the error due to the ambiguity in the s-wave p-7Be scattering length. This
value of S17(0) differs from the one extracted with the first-order
perturbation theory including Coulomb breakup by dipole transitions: 18.9 +/-
1.8 eV b. It turns out that the difference is due to the inclusion of the
nuclear and Coulomb-quadrupole transitions and multi-step processes of
all-order in the present work. The p-7Be interaction potential used in the CDCC
calculation is also used in the ANC analysis of 7Be(p,\gamma)8B. The value of
S17(0)=21.7 +0.62/-0.55 eV b obtained is consistent with the previous one
obtained from a precise measurement of the p-capture reaction cross section
extrapolated to zero incident energy, S17(0)=22.1 +/- 0.6 (expt) +/- 0.6 (theo)
eV b, where (theo) stands for the error in the extrapolation. Thus, the
agreement between the values of S17(0) obtained from direct 7Be(p,\gamma)8B and
indirect 8B-breakup measurements is significantly improved.Comment: 13 pages, 9 figures, published in PR
Stau-catalyzed Li Production in Big-Bang Nucleosynthesis
If the gravitino mass is in the region from a few GeV to a few 10's GeV, the
scalar lepton X such as stau is most likely the next lightest supersymmetry
particle. The negatively charged and long-lived X^- may form a Coulomb bound
state (A X) with a nucleus A and may affect the big-bang nucleosynthesis
through catalyzed fusion process. We calculate a production cross section of
Li6 from the catalyzed fusion (He4 X^-) + d \to Li6 + X^- by solving the
Schr\"{o}dinger equation exactly for three-body system of He4, d, and X. We
utilize the state-of-the-art coupled-channel method, which is known to be very
accurate to describe other three-body systems in nuclear and atomic reactions.
The importance of the use of appropriate nuclear potential and the exact
treatment of the quantum tunneling in the fusion process are emphasized. We
find that the astrophysical S-factor at the Gamow peak corresponding to T=10
keV is 0.038 MeV barn. This leads to the Li6 abundance from the catalyzed
process as Li6|_{CBBN}\simeq 4.3\times 10^{-11} (D/2.8\times 10^{-5})
([n_{X^-}/s]/10^{-16}) in the limit of long lifetime of X. Particle physics
implication of this result is also discussed.Comment: 16 pages, 7 figure
On the possibility of generating a 4-neutron resonance with a {\boldmath } isospin 3-neutron force
We consider the theoretical possibility to generate a narrow resonance in the
four neutron system as suggested by a recent experimental result. To that end,
a phenomenological three neutron force is introduced, in addition to a
realistic interaction. We inquire what should be the strength of the
force in order to generate such a resonance. The reliability of the
three-neutron force in the channel is exmined, by analyzing its
consistency with the low-lying states of H, He and Li and the
scattering.
The {\it ab initio} solution of the Schr\"{o}dinger equation is obtained
using the complex scaling method with boundary conditions appropiate to the
four-body resonances. We find that in order to generate narrow resonant
states a remarkably attractive force in the channel is required.Comment: 11 pages, 11 figures, minor change, published version, to be
published in Physical Review
Relativistic continuum-continuum coupling in the dissociation of halo nuclei
A relativistic coupled-channels theory for the calculation of dissociation
cross sections of halo nuclei is developed. A comparison with non-relativistic
models is done for the dissociation of B projectiles. It is shown that
neglecting relativistic effects leads to seizable inaccuracies in the
extraction of the astrophysical S-factor for the proton+beryllium radiative
capture reaction.Comment: 4 pages, 2 figures, version accepted for publication at Physics
Review Letter
Role of quark-quark correlation in baryon structure and non-leptonic weak transitions of hyperons
We study the role of quark-quark correlation in the baryon structure and, in
particular, the hyperon non-leptonic weak decay, which is sensitive to the
correlation between quarks in the spin-0 channel. We rigorously solve
non-relativistic three-body problem for SU(3) ground state baryons to take into
account the quark-pair correlation explicitly. With the suitable attraction in
the spin-0 channel, resulting static baryon properties as well as the parity
conserving weak decay amplitudes agree with the experimental values. Special
emphasis is placed also on the effect of the SU(6) spin-flavor symmetry
breaking on the baryon structure. Although the SU(6) breaking effects on the
local behavior of the quark wave functions are considerable due to the spin-0
attraction, the calculated magnetic moments are almost the same as the naive
SU(6) expectations
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