Bruce H. J. McKellar

The two-pion-exchange three-nucleon potential and nuclear matter

We derive the complete three-nucleon potential of the two-pion-exchange type, suitable for nuclear structure calculations, by extending away from the forward direction the subthreshold off-pion-mass-shell πN scattering amplitude of Coon, Scadron and Barrett. The off-mass-shell extrapolation, subject to current algebra and PCAC constraints, yields approximately model independent amplitudes (in that they depend primarily on πN data) in the complete potential. The subtraction of the forward propagating nucleon term from the amplitudes is done in greater generality than before. The contribution of this three-nucleon potential to the binding energy of symmetric nuclear matter is estimated using the perturbative formalism of McKellar and Rajaraman. In our treatment of correlations in nuclear matter, the dominant three-nucleon potential has strong components from both s-wave and p-wave πN scattering. A three-body potential based on the p-wave Δ isobar can be considered a special case of the derived potential. Therefore, we are able to trace most of the discrepancies in previously reported binding energy contributions back to the assumed energy denominator in second order. We find the contribution of the three nucleon potential to the energy of symmetric nuclear matter to be − 1.90 ± 0.2 MeV.

Topological phase due to electric dipole moment and magnetic monopole interaction

We show that there is a dual Aharonov-Casher topological effect [Phys. Rev. Lett. 53, 319 (1984)] on a neutral particle with electric dipole moment interacting with a magnetic field produced by magnetic monopoles.

The Scaling Group of the Radiative Transfer Equation

Abstract We show that the equation of radiative transfer is invariant under a group of simultaneous transformations of the scale (i.e., the optical thickness) and the phase function. In this way, we provide a unified explanation of various empirical scaling laws, similarity relations and other approximations (especially delta-function approximations) which have been proposed in the literature. Connections with critical-point behavior in statistical mechanics are also indicated.

The Foldy{Wouthuysen transformation

The Foldy–Wouthuysen transformation of the Dirac Hamiltonian is generally taught as simply a mathematical trick that allows one to obtain a two‐component theory in the low‐energy limit. It is not often emphasized that the transformed representation is the only one in which one can take a meaningful classical limit, in terms of particles and antiparticles. We briefly review the history and physics of this transformation.

DEUTERON STRIPPING ANALYSIS.

Abstract A new method is developed for the study of deuteron stripping reactions. The aim is to circumvent a difficulty associated with the usual DWBA approach. This is that the approximation of assuming zero internal deuteron distortion is made in a matrix element which receives its contributions from that region of configuration space within or near the initial nucleus. As this is the same region in which deuteron polarization is likely to be most important, it may be that the DWBA approach is inherently incapable of yielding accurate determinations of spectroscopic factors. In the present method the cross section is expressed in terms of a matrix element which differs in form from that usually employed, while an explicit function S (1 − S) 2 of the spectroscopic factor S emerges as a multiplying factor. It appears that this form for the cross section has the following advantages: (a) in the matrix element involved, the deuteron elastic scattering wavefunction contributes primarily in the asymptotic region of configuration space for which there is no internal deuteron distortion, while effects arising from the neutron and proton influenced differently by the core nucleus appear in terms of neutron and proton optical wavefunctions only; (b) a large part of the structure, or S , dependence of a specific reaction has been extracted in the factor S (1 − S) 2 so that the matrix element itself is less sensitive to specific structure details than the usual DWBA matrix element; (c) an evaluation of the differential cross section depends primarily on a knowledge of neutron and proton optical wavefunctions, and the results are not significantly dependent on any particular choice of optical model parameters provided these are consistent with nucleon scattering data. Differential cross sections have been calculated for six ground-state reactions covering a wide range of mass numbers; comparisons with experimental results are highly encouraging.

THE NEUTRON ELECTRIC DIPOLE MOMENT

We have made a systematic study of the electric dipole moment (EDM) of neutron Dn in various models of CP violation. We find that (i) in the standard KM model with 3 families, the neutron EDM is in the range 1.4 × 10−33 ≤ |Dn| ≤ 1.6 × 10−31e.cm, (ii) the two Higgs doublet model has approximately the same value of Dn as the standard model, (iii) Dn in the Weinberg model is predicted to satisfy |Dn| > 10−25e.cm, (iv) in a class of left-right symmetric models Dn is of the order of 10−26±1e.cm, (v) in supersymmetric models, Dn is of order 10−22ϕ e.cm with ϕ being the possible phase difference of gluino mass and the gluino-quark-squark mixing matrix, (vi)the strong CP parameter θ is found to be θ < 10−9, using the present experimental limit that |Dn| < 2.6 × 10−25e.cm with 90% confidence.

The neutron electric dipole moment in the standard KM model

Abstract We compute the electric dipole moment of the neutron in the standard KM model, including the meson-baryon intermediate states which dominate the result in the SU(3) × SU(3) chiral limit, and find 1.4×10−31 e cm⩾|Dn|⩾9.9×10−33 e cm.

Analytic inversion of multispectral extinction data in the anomalous diffraction approximation.

We obtain a simple integral formula for the radius distribution function or polydispersion n(r) in terms of the multispectral extinction τ(k), where k is the wavenumber. This formula is valid when the extinction coefficient is given by the anomalous diffraction approximation and n(r) vanishes faster than r∊ as r → 0 for some positive ∊.

Probing large distance higher dimensional gravity from lensing data

Abstract The modifications induced in the standard weak-lensing formula if Newtonian gravity differs from inverse square law at large distances are studied. The possibility of putting bounds on the mass of gravitons from lensing data is explored. A bound on graviton mass, estimated to be about 100 Mpc −1 is obtained from analysis of some recent data on gravitational lensing.

The influence of mixing of finite mass neutrinos on beta decay spectra

Abstract It is shown that neutrino mixing, of the type required for neutrino oscillations, will complicate efforts to determine the electron neutrino mass from β decay spectra. The shape of the spectra will depend on the masses and mixing angles of all neutrinos which couple to the electron neutrino.