Polarization effects in elastic electron deuteron scattering

The vector and tensor polarization of the deuteron after scattering and the dependence of the cross section on the polarization before scattering are given for elastic electron deuteron scattering treating the deuteron as a spin 1 elementary particle characterized by three electromagnetic formfactors and describing the interaction by the first Born approximation. By using polarization measurements a separation of the charge and quadrupole formfactors may be accomplished, and thus the assumptions may be tested, which are necessary for the extraction of the isoscalar nucleon formfactors from the deuteron formfactors.     

Formfactors for one- and two-nucleon transfer reactions induced by light and heavy ions

Formfactors and overlaps for light and heavy ion transfer reactions are evaluated including finite range and recoil effects. The treatment of the recoil is based on a separation into a transversal effect, responsible for a modification of the selection rules, and a longitudinal effect related to a scaling of the radial motion. The formfactors for multinucleon transfer can in this formulation be obtained either as products of single-particle overlaps and formfactors or, after transformation to center of mass and relative motion, in terms of cluster type representation. The extension of the nuclear field theory to include transfer reactions is indicated. Some examples of the application of the formfactors to calculations of cross sections by means of distorted wave Born approximation are given with the main emphasis on heavy ion reactions.     

Local magnetic field distributions in superconducting niobium at 4.2 K by neutron diffraction

Neutron diffraction experiments on flux line lattices in superconducting Nb are reported. From the integral reflectivities of the (10), (11), (20), (21) and (31) reflections the absolute values of the formfactors were obtained as a function of the flux density. Considering certain properties of the flux line lattice it is also possible to determine the phases of the formfactors. From this the local field distribution in the mixed state could be calculated by Fourier-transformation. The dependence of the resulting maximum, minimum, and saddle point fields on the flux density and on the impurity parameter is discussed and compared with theory.     

Hadron scattering in an additive eikonal quark model

Total and differential cross sections for p?p, pp, π^±p, K^+-p and Ψp at high energies are analysed in an additive eikonal quark model. It is shown that the exceptionally small Ψp slope contradicts the Chou-Yang model at present energies but can be accounted for by a quark-quark potential with different ranges for different pairs of quarks. This leads to smaller rms radii for hadrons than those derived from e.m. formfactors, implying that the constituent quarks have formfactors. Predictions for hadron-neutron and strange and charmed hadron-nucleon scattering are derived.     

Constructive proposals for QFT based on the crossing property and on lightfront holography

The recent concept of modular localization of wedge algebras suggests two methods of classifying and constructing QFTs, one based on particle-like generators of wedge algebras using on-shell concepts (S-matrix, formfactors: crossing property) and the other using the off-shell simplification of lightfront holography (chiral theories). The lack of an operator interpretation of the crossing property is a serious obstacle in on-shell constructions. In special cases, one can define a “masterfield” whose connected formfactors constitute an auxiliary thermal QFT for which the KMS cyclicity equation is identical to the crossing property of the formfactors of the master field. Further progress is expected to result from a conceptual understanding of the role of on-shell concepts as particle states and the S-matrix within the holographic lightfront projection.     

Local current commutators

The predictive power of current algebra relations is discussed using models for the spectral functions of current commutator matrix elements. The functions constructed fulfill the requirements of covariance, locality and spectrum conditions. Thus, the current algebra constraints can easily be imposed. In these models the formfactors are described by superpositions of poles. For simplicity only spin zero states are taken into account.     

Relativistically covariant calculation of hyperon formfactors

Electroweak formfactors are calculated using a Lorentz invariant formalism based on boosted bag-model. The Lorentz-invariance is explicitly demonstrated. Only one version of the formalism can be consistent with the conserved vector current (CVC) constraint. Some connections with the quasi-potential formalism are discussed. Difficulties encountered in the usage of the chiral-bag model are described. The results are compared with the earlier bag model calculations for semileptonic weak decays.     

Macroscopic formfactors for pair transfer in heavy ion reactions

A case is made for the use of macroscopic formfactors for nucleon pair transfer in heavy ion reactions. The formalism is based on the identification of a local pair transition density whose radial dependence can be converted in a macroscopic transfer formfactor related to the ion-ion potential in a similar way as it has traditionally been done for inelastic excitations.     

A survey of band-gap renormalization in quantum well structures

The band-gap renormalization at finite temperatures in quantum wells is calculated from the dynamical self energy. Sublevel formfactors and non-diagonal screening are taken into account. In order to compare with these calculations, the chemical potential and the carrier density in the active layer of a quantum-well laser diode are determined experimentally based on a novel non-spectroscopic method.     

Asymptotic behaviour of weak formfactors within QCD

The highq ²-behaviour of the six weak nucleon (quasi-)elastic formfactors as calculated from lowest order (two-gluon exchange) in QCD is presented. The expressions are also parametrized in the usual way by dipole (triplepole) formulae.     

Predictions for the electromagnetic formfactors of baryons from hybrid groups

The predictions of the hybrid groupSU ₃?SU ₃?U ₁ for the electromagnetic formfactors of baryons are studied in detail. Surprisingly, this small group leads already to strong restrictions. For example, it gives for the ratio of the magnetic formfactors of neutron and proton ?2/3 for all values of the momentum transfer variable. The results of the powerful (SU ₆) _W hybrid group which involves more speculative assumptions are also quoted. In addition, the theoretical foundation of the hybrid groups is discussed in the paper.     

The continuous spectrum and the excitation of giant resonances in the reaction 16O + 208Pb

Recent data on the inelastic scattering of ¹⁶O on ²⁰⁸Pb at 315 MeV provide a crucial test of the coherent state model of heavy ion reactions where the surface degrees of freedom are explicitly taken into account. The transfer of particles is treated as a position dependent absorption in accordance with one-particle transfer formfactors.     

Semileptonic decays of heavy to light mesons from an MIT bag model

Using the (modified) MIT bag model we calculated formfactors and decay widths for pseudoscalar-pseudoscalar and pseudoscalar-vector semileptonic decays of heavy to light mesons. We discuss the physical phenomena which are important in these processes and their influence on the measurable quantities. Our results are consistent with the available experimental data. A comparison with the results of other models is also given.Work supported by the KBN grant no. 2P30207607     

An analytical folding potential for deformed nuclei

Concentrating on nucleon- andα-nucleus interactions the folding approach is applied to light deformed target nuclei. The analytically evaluated potentials depend onl. Forl=0, 2 and 4 the formulae for the elastic and inelastic interactions are given discussing also the effect of different forces and charge distributions on the formfactors.     

Uniqueness of inverse scattering problem in local quantum physics

It is shown that the a Bisognano-Wichmann-Unruh inspired formulation of local quantum physics which starts from wedge-localized algebras, leads to a uniqueness proof for the scattering problem. The important mathematical tool is the thermal KMS aspect of localization and its strengthening by the requirement of crossing symmetry for generalized formfactors.     

Coulombformfaktoren für7Li

Using refined clustermodel wave functions the Coulomb form factors for the elastic scattering of electrons as well as the formfactors for the inelastic scattering leading to the first and second excited states of⁷Li have been calculated.     

A Critical Look at 50 Years Particle Theory from the Perspective of the Crossing Property

The crossing property is perhaps the most subtle aspect of the particle-field relation. Although it is not difficult to state its content in terms of certain analytic properties relating different matrixelements of the S-matrix or formfactors, its relation to the localization- and positive energy spectral principles requires a level of insight into the inner workings of QFT which goes beyond anything which can be found in typical textbooks on QFT. This paper presents a recent account based on new ideas derived from “modular localization” including a mathematic appendix on this subject. Its main achievement is the proof of the crossing property from a two-algebra generalization of the KMS condition.     

Kovariante Dichten. Probleme der Makrokausalität und Teilchendichte in der relativistischen Wellenmechanik. I

We consider signals represented by skalar particle densities ?. It is then proven that the assumptions (i) ? ≥ s° (ii) ? = s⁰ is the fourth component of a four-vector s^μ (iii) the scalar particles form a repesentation of the POINCARÉ group in HILBERT space, are incompatible with experimental data (formfactors of pions).     

The induced pseudoscalar interaction and the μ-capture in He3

Recent measurements ofμ-capture in He³ as well as the determination of the electric and magnetic formfactors of He³ and H³ allow a detailed analysis of theμ-capture process in He³. Assuming only the theory of a conserved vector current these experiments can be used to derive a relation for the axial vector part of the He³→H³ transition amplitude. This result is compared with a nuclear physics calculation of the formfactors. It follows that the induced pseudoscalar coupling constant for the muon capture on a free proton has a sign in agreement with the value predicted byGoldberger andTreiman. Its magnitude seems to be somewhat larger than the predicted value. We also find qualitative agreement with an extension ofNambu's idea of an almost conserved axial vector current to the case of the He³→H³ transition.