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 $^{11}$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 WWγWW\gamma couplings

A next-to-leading log calculation of the reactions $pp$ and $p\overline{p}\rightarrow W^\pm\gamma X$ 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 $WW\gamma$ 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 $WW\gamma$ 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