120238308
Subshell branching ratios of partial photoionization cross sections
122939851
Nonstatistical behavior of photoeffect subshell branching ratios at high energies
122353805
Screening effects in radiative orbital electron capture by an atomic nucleus
121398906
Generalized Fermi-Segrè formula
123462298
Overlap of shape resonance and Cooper-minimum structure in photoionization
Examples of a Cooper minimum inside the range of a shape-resonance maximum of a photoionization cross section have been found in numerical calculations within a single-electron model in a relativistic Hartree-Fock-Slater potential. In these model calculations for the photoionization of tin and uranium we find relatively broad shape resonances in all the $d$ and $f$ subshells. In addition a Cooper minimum occurs in the outer subshells of these high-angular-momentum states within the region of the shape-resonance maximum. We examine the matrix elements for these subshells and the resulting cross sections and angular distributions.
119835686
Connection between the bremsstrahlung tip and direct radiative recombination: angular distributions and polarization correlations
We illustrate the possibility for calculation of bremsstrahlung tip angular distributions and polarization correlations from corresponding photoeffect results with an extension of the method for connecting bremsstrahlung tip and direct-radiative-recombination (DRR) cross sections developed by Lee and Pratt. The agreement between results obtained with this method and results from our numerical partial-wave calculations is, in general, satisfactory. We note features of the distributions and correlations, and once again point out the inadequacies of the nonrelativistic dipole approximation for the evaluation of bremsstrahlung or DRR angular distributions.
120290177
Covariant Harmonic Oscillators and Excited Baryon Decays
We use the covariant harmonic oscillator wave functions to study the decay matrix elements of the excited baryonic resonances. It is pointed out that the harmonic oscillator wave function is suitable for the description of relativistic extended particles. We use the probability concept of the covariant harmonic oscillator wave functions and the covariant Dirac spinors to calculate the Jrr decays of the F,. (1690), D,. (1690) and D,. (1520) resonances. Our numerical results are in good agreement with the measurable ratios in these decay processes.
119339738
Photon spin as a rotation in gauge space
It is shown that the photon spin is associated with the rotational invariance in a two-dimensional space spanned by the two ''translation'' parameters of the E(2)-like little group of the Poincare group. Since the translation in the E(2)-like space is a gauge transformation, the photon spin can be associated with an orbitlike rotation with nonzero radius in the gauge space.
8523168
Fixed-Point Analysis of the Low-Energy Constants in the Pion-Nucleon Chiral Lagrangian
In the framework of heavy-baryon chiral perturbation theory, we investigate the fixed point structure of renormalization group equations (RGE) for the ratios of the renormalized low energy constants (LECs) that feature in the pion-nucleon chiral Lagrangian. The ratios of the LECs deduced from our RGE analysis are found to be in semi-quantitative agreement with those obtained from direct fit to the experimental data. The naturalness of this agreement is discussed using a simple dimensional analysis combined with Wilsonian RGEs.
14379054
Covariant Model of Relativistic Extended Particles based on the Oscillator Representation of the Poincaré Group
While internal space-time symmetries of relativistic particles are dictated by the little groups of the Poincaré group, it is possible to construct representations of the little group for massive particles starting from harmonic oscillator wave functions for the quark model. The resulting oscillator wave functions are covariant and can be Lorentz-boosted. It is thus possible to obtain the parton model by boosting the quark model. A review of Wigner's theory of the little groups is given. It is shown that the covariant oscilla-tor wave functions become squeezed as as the system becomes boosted. It is shown also that the Lorentz-squeezed quark distribution exhibits the peculiarities of Feynman's parton model including the lack of coherence in the calculation of cross sections. A historical review of the concept of covariance is given.
122940721
LORENTZ CONTRACTION OF THE BETHE--SALPETER GREEN'S FUNCTION.