Michael Danos

On the long-range correlation model of the photonuclear effect

Abstract The long-range correlation model, i.e. the hydrodynamic “second-sound” model, of the photonuclear effect predicts a splitting of the giant resonance in deformed nuclei. As a result of this, the width and the shape of the observed resonance will be different in different nuclei. The hydrodynamic model further predicts the existence of a second-sound monopole mode at roughly twice the energy of the dipole mode. However, the resonance energy is so high that this mode may be damped completely except, perhaps, in the heaviest nuclei. Observation of this mode could yield information about the energy dependence of the friction coefficient Γ of second sound in nuclear matter.

Image information content and patient exposure

Presently, patient exposure and x-ray tube kilovoltage are determined by image visibility requirements on x-ray film. With the employment of image-processing techniques, image visibility may be manipulated and the exposure may be determined only by the desired information content, i.e., by the required degree of tissue-density descrimination and spatial resolution. This work gives quantitative relationships between the image information content and the patient exposure, give estimates of the minimum exposures required for the detection of image signals associated with particular radiological exams. Also, for subject thickness larger than approximately 5 cm, the results show that the maximum information content may be obtained at a single kilovoltage and filtration with the simultaneous employment of image-enhancement and antiscatter techniques. This optimization may be used either to reduce the patient exposure or to increase the retrieved information.

Multipole Matrix Elements of the Translation Operator

Formulas are given for the expansion of multipole fields of arbitrary tensorial character into multipole fields about a shifted origin. The expansion coefficients are given as matrix elements of the translation operator. In analogy to the matrix elements of the rotation operator, we introduce for these matrix elements a standard form which represents a parallel displacement of the coordinate system along the z axis. Any arbitrary translation of the coordinate system then consists of a consecutive application of a rotation, a standard translation, and a rotation. Since the multipole fields form a complete set any arbitrary function can in principle be expressed in a shifted coordinate system by means of the given formulas. All mathematical derivations are given.

The importance of the reaction volume in hadronic collisions

Abstract The pair production in the thermodynamic model is shown to depend sensitively on the (hadronic) reaction volume. Strangeness production in nucleus-nucleus collisions is treated as an example.

Baryon resonances in nuclei with applications to the two-nucleon system

Abstract The non-relativistic description of the nucleus is presented which allows the possibility of excited baryon resonances within the nucleus via collision of the nucleons with exchanged mesons. A perturbative treatment for the intrinsically excited configurations is justified, and lowest order results for the wave functions of the excited configurations are derived. Detailed formulae for the two-nucleon system are presented and numerical results are given to show the effect of the baryon resonances on the magnetic moment and threshold photodisintegration of the deuteron.

CERENKOV RADIATION FROM EXTENDED ELECTRON BEAMS

The Cerenkov radiation emitted by a bunched electron beam passing along a dielectric material at a close distance is calculated for a flat beam near a plane surface, a flat beam between two plane surfaces and for a circularly cylindrical beam within a cylindrical hole.

Fractals and Chaos in Geology and Geophysics, Second Edition

Fractals and Chaos in Geology and Geophysics, Second Edition, is the best technical introduction to chaos known to me. It is suitable not only for geologists, but for anyone who is seriously interested in the subject. The title of the book is misleadingly narrow; its content would be better described by the unwieldy title “Concepts and Application of Chaos Theory,” with an even longer subtitle “Examples Taken Predominantly from the Earth Sciences.” The mathematics are simple; a second-year college student should be fully capable of handling the book.

A microscopic description of the (γ, pn )-reaction

The quasideuteron process has been investigated for photon energies 40 MeV<Eγ< 160 MeV on the basis of a shell model picture modified by short range nucleon-nucleon correlations. It turns out that the cross section for the (γ,pn)-reaction depends sensitively on the details of the correlation function, i.e. on the exchange of high momenta between otherwise independently moving nucleons. The final state interaction has been consistently taken care of by using optical model wave functions for the outgoing nucleons. The results of the calculations for16O indicate that precise measurements of the (γ,pn) cross section do contain information on the properties of the nuclear wave functions for small internucleonic distances.

Possible signature for and early hadronization mechanisms of quark-gluon plasma

Abstract We consider the ratio of particle abundances radiated from quark-gluon plasma above mean thermal energy and point out signigicant differences expected as compared with global particle yields. Two microscopic processes leading to medium to high E ⊥ abundances are quantitatively considered and the means of determining the plasma baryochemical potential are discussed. Strong anomalies in strange antibaryon spectra are found, characteristic of the formation of quark-gluon plasma.

Baryon resonances in nuclei: magnetic moments of the deuteron

Abstract Baryon resonance admixtures to the p-n system have been calculated, as well as their effect on the static and transition magnetic moments of the deuteron.