Electromagnetic reactions of few-body systems with the Lorentz integral transform method

Various electromagnetic few-body break-up reactions into the many-body continuum are calculated microscopically with the Lorentz integral transform (LIT) method. For three- and four-body nuclei the nuclear Hamiltonian includes two- and three- nucleon forces, while semirealistic interactions are used in case of six- and seven-body systems. Comparisons with experimental data are discussed. In addition various interesting aspects of the $^4$He photodisintegration are studied: investigation of a tetrahedrical symmetry of $^4$He and a test of non-local nuclear force models via the induced two-body currents.Comment: 8 pages with 6 figures, invited talk at the 18th International IUPAP Conference on Few-Body Problems in Physics, Santos-S.Paulo, August 21-26, 200

The Lorentz integral transform (LIT) method

The LIT approach is reviewed both for inclusive and exclusive reactions. It is shown that the method reduces a continuum state problem to a bound-state-like problem, which then can be solved with typical bound-state techniques. The LIT approach opens up the possibility to perform ab initio calculations of reactions also for those particle systems which presently are out of reach in conventional approaches with explicit calculations of many-body continuum wave functions. Various LIT applications are discussed ranging from particle systems with two nucleons up to particle systems with seven nucleons.Comment: Lectures delivered at the 4th DAE-BRNS Workshop on Hadron Physics, AMU, Aligarh, India, Feb. 18-23, 2008; 23 pages, 16 figure

Complete Sets of Polarization Observables in Electromagnetic Deuteron Break-up

For deuteron photo- and electrodisintegration the selection of complete sets of polarization observables is discussed in detail by applying a recently developed new criterion for the check of completeness of a chosen set of observables. The question of ambiguities and their resolution by considering additional observables is discussed for a numerical example, for which the role of experimental uncertainties is also investigated. Furthermore, by inversion of the expressions of the observables as hermitean forms in the $t$-matrix elements a bilinear term of the form $t_{j'}^*t_j$ can be given as a complex linear form in the observables from which an explicit solution for $t_j$ in terms of observables can be obtained. These can also be used to select sets of observables for the explicit representation of the $t$-matrix.Comment: 37 pages revte

General Multipole Expansion of Polarization Observables in Deuteron Electrodisintegration

Formal expressions are derived for the multipole expansion of the structure functions of a general polarization observable of exclusive electrodisintegration of the deuteron using a longitudinally polarized beam and/or an oriented target. This allows one to exhibit explicitly the angular dependence of the structure functions by expanding them in terms of the small rotation matrices $d^j_{m'm}(\theta)$, whose coefficients are given in terms of the electromagnetic multipole matrix elements. Furthermore, explicit expressions for the coefficients of the angular distributions of the differential cross section including multipoles up to $L_{max}=3$ are listed in tabular form.Comment: 23 pages revtex including one figure, accepted for Eur.Phys. J.