7,785 research outputs found
Direct Reactions with Exotic Nuclei
We discuss recent work on Coulomb dissociation and an effective-range theory
of low-lying electromagnetic strength of halo nuclei. We propose to study
Coulomb dissociation of a halo nucleus bound by a zero-range potential as a
homework problem. We study the transition from stripping to bound and unbound
states and point out in this context that the Trojan-Horse method is a suitable
tool to investigate subthreshold resonances.Comment: 9 pages, 1 figure, proceedings of Workshop on "Reaction Mechanisms
for Rare Isotope Beams" Michigan State University March 9-12,200
Investigation of subthreshold resonances with the Trojan horse method
It is pointed out that the Trojan horse method is a suitable tool to
investigate subthreshold resonances.Comment: references added, typo corrected;6 pages, 1 figure, to be published
in the AIP Proceedings of Fusion06, International Conference on Reaction
Mechanisms and Nuclear Structure at the Coulomb Barrier, March 19-23, 2006,
San Servolo, Ital
Direct Reactions with Exotic Nuclei, Nuclear Structure and Astrophysics
Intermediate energy Coulomb excitation and dissociation is a useful tool for
nuclear structure and astrophysics studies. Low-lying strength in nuclei far
from stability was discovered by this method. The effective range theory for
low-lying strength in one-neutron halo nuclei is summarized and extended to
two-neutron halo nuclei. This is of special interest in view of recent rather
accurate experimental results on the low-lying electric dipole strength in
Li. Another indirect approach to nuclear astrophysics is the Trojan
horse method. It is pointed out that it is a suitable tool to investigate
subthreshold resonances.Comment: 8 pages, 2 figures, Proceedings of the Erice School on 'Radioactive
Beams, Nuclear Dynamics and Astrophysics' to be published in 'Prog. Part.
Nucl. Phys.
Hadron collider limits on anomalous couplings
A next-to-leading log calculation of the reactions and
is presented including a tri-boson
gauge coupling from non-Standard Model contributions. Two approaches are made
for comparison. The first approach considers the tri-boson coupling
as being uniquely fixed by tree level unitarity at high energies to its
Standard Model form and, consequently, suppresses the non-Standard Model
contributions with form factors. The second approach is to ignore such
considerations and calculate the contributions to non-Standard Model tri-boson
gauge couplings without such suppressions. It is found that at Tevatron
energies, the two approaches do not differ much in quantitative results, while
at Large Hadron Collider (LHC) energies the two approaches give significantly
different predictions for production rates. At the Tevatron and LHC, however,
the sensitivity limits on the anomalous coupling of are too weak to
usefully constrain parameters in effective Lagrangian models.Comment: Revtex 23 pages + 8 figures, UIOWA-94-1
Theory of the Trojan-Horse Method
The Trojan-Horse method is an indirect approach to determine the energy
dependence of S-factors of astrophysically relevant two-body reactions. This is
accomplished by studying closely related three-body reactions under quasi-free
scattering conditions. The basic theory of the Trojan-Horse method is developed
starting from a post-form distorted wave Born approximation of the T-matrix
element. In the surface approximation the cross section of the three-body
reaction can be related to the S-matrix elements of the two-body reaction. The
essential feature of the Trojan-Horse method is the effective suppression of
the Coulomb barrier at low energies for the astrophysical reaction leading to
finite cross sections at the threshold of the two-body reaction. In a modified
plane wave approximation the relation between the two-body and three-body cross
sections becomes very transparent. The appearing Trojan-Horse integrals are
studied in detail.Comment: 27 pages, REVTeX4, 4 figures, 1 tabl
E0 emission in alpha + ^12C fusion at astrophysical energies
We show that E0 emission in alpha + ^12C fusion at astrophysically
interesting energies is negligible compared to E1 and E2 emission.Comment: submitted to Phys. Rev. C, Brief Report
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