2,074 research outputs found
Antiproton-proton partial-wave analysis below 925 MeV/c
A partial-wave analysis of all antiproton-proton scattering data below 925
MeV/c antiproton laboratory momentum is presented. The method used is adapted
from the Nijmegen phase-shift analyses of pp and np scattering data. The
Nijmegen 1993 antiproton-proton database, consisting of 3646 antiproton-proton
scattering data, is presented and discussed. The best fit to this database
results in chi^2_min/Ndata = 1.043. The pseudovector coupling constant of the
charged pion to nucleons is determined to be (f_c)^2 = 0.0732(11) at the pion
pole, where the error is statistical.Comment: Report THEF-NYM 93.02 42 pages REVTeX, 7 separate postscript figures
appended. Accepted for publication in Phys. Rev.
Deuteron Dipole Polarizabilities and Sum Rules
The scalar, vector, and tensor components of the (generalized) deuteron
electric polarizability are calculated, as well as their logarithmic
modifications. Several of these quantities arise in the treatment of the
nuclear corrections to the deuterium Lamb shift and the deuterium hyperfine
structure. A variety of second-generation potential models are used and a
(subjective) error is assigned to the calculations. The zero-range
approximation is used to analyze a subset of the results, and a simple
relativistic version of this approximation is developed.Comment: 14 pages, LaTex - submitted to Physical Review
The generation of offshore tidal sand banks and sand waves
A simple morphological model is considered which describes the interaction between a tidal flow and an erodible bed in a shallow sea. The basic state of this model describes a spatially uniform tide over a flat bottom where the flow vector is represented as a tidal ellipse. The linear stability of this solution is analysed with respect to bed form perturbations. Results are presented for both a uni-directional and circular tide. In the former case the wave-length and the orientation of the fastest growing bed mode agree well with those of tidal sand banks. However, this model only predicts the growth of large-scale sand ridges. With a simplified numerical model we tentatively show that the effects of secondary currents on the sediment transport trigger the formation of instabilities at an essentially smaller scale, viz, sand waves. Another limitation of a model with uni-directional tides is that no selective modes found are the first to become unstable if the model parameters are varied. In the case of a circular tide, critical model parameters are found below which the basic state is stable. We conclude that this provides a starting point for the development of a weakly non-linear analysis, which will yield information on the amplitude behaviour of marginally growing bed forms
- …