Transition amplitudes and probabilities for the Weinberg-Salam model

Transition probabilities for the processes vv?vv, vv?, $\text{vv}$?$\text{vv}$, and spin-dependent transition amplitudes for the processes ve?ve, vē?vē, v?e?v?e, $\text{ve}$?$\text{ve}$ and vv??eē are calculated in lowest order for the Weinberg-Salam model.     

Spectroscopy of states in 33S by means of neutron-gamma angular correlation measurements

Levels of ³³S for E_x < 5 MeV have been studied with the ³⁰Si(α, nγ)³³S reaction at bombarding energies of E_α = 7.5 and 10.2 MeV. Neutron-gamma angular correlation experiments lead to three unambiguous spin and parity assignments: $\text{J}{}^{\mathrm{\pi }}\text{(3.83) =}\text{5}\text{2}{}^{\mathrm{+}}\text{, J}{}^{\mathrm{\pi }}\text{(4.048) =}\text{9}\text{2}{}^{\mathrm{+}}\text{and}\text{J}{}^{\mathrm{\pi }}\text{(4.09) =}\text{7}\text{2}{}^{\mathrm{+}}$. The measured branching and mixing ratios yield transition strengths for dipole and quadrupole transitions.     

Scattering length and effective range in closed form for the Coulomb plus Yamaguchi potential

From the known expression for the off-shell T-matrix corresponding to the potential consisting of the sum of the Coulomb potential and the Yamaguchi potential, the physical scattering amplitude can be derived in a satisfactory way. We derive simple exact closed formulae for the scattering length a_cs and the effective range r_cs from this amplitude. These are compared with approximate formulae derived by Harrington. Also a few numerical calculations are reported and compared with results obtained by Harrington and by Ali et al.     

A low-lying resonance in the spectrum of H

It was proved by Pekeris⁽¹⁾ that the singly excited states of H^- lie exactly at, or slightly above, the ground state of hydrogen. Using a theory of Fano,⁽²⁾ these fictitious states will have a configuration interaction with the H^- continuum. The strength of this configuration interaction is computed for the mixing of a 1s2p¹P⁰ state with the H^- continuum for different values of the fictitious binding energy of the 2p valence electron. In every case, the effect of the configuration interaction is to induce a rapid change of the phase shift of the continuum wave function by a quantity of π/2 over an energy range of a few times 0.01 eV, at an energy somewhat above the hydrogen ground state. The variation from π/2 to π is much slower. Such a swift change of the phase shift may be identified with the occurrence of a low-lying shape resonance.     

Nonexistence of localized band tail states in substitutional semiconductor alloys and some other disordered systems

A recent theory of semiconducting glasses seems to imply a substantial density of localized band tail states in substitutional semiconductor alloys, such as Sie or GaAsP, and also in homogenous strain-free amorphous Si and Ge. Experimental evidence against the existence of such states in these non-glassy disordered materials is overwhelming. The paradox is resolved by noting that if the material is in thermodynamic equilibrium, the disorder of the atomic potentials will not result in disorder of the valence or conduction band energy levels.     

The Callan-Symanzik equation and dimensional regularization

A study is made of the Callan-Symanzik equation using the dimensional regularization method. The final equation is far more general than in the usual derivation in that the effect of mass terms is explicitly included; moreover the momenta need not be restricted to the deep-Euclidean region when considering asymptotic limits.     

Isobaric analogue resonances in proton elastic scattering from 84Sr

The cross section for the reaction ⁸⁴Sr(p, p₀)⁸⁴Sr has been measured for proton energies in the range E_p = 4.18?6.73 MeV. Resonance parameters were determined for 15 isobaric analogue resonances. Spectroscopic factors calculated for the analogues by means of the R-matrix theory and the Green function method are compared with Spectroscopic factors determined from the ⁸⁴Sr(d, p)⁸⁵Sr reaction. Angular distributions were measured at E_p = 7 and 12 MeV in order to obtain optical model parameters.     

Elastic scattering of 40Ar on 40Ca at Elab = 191, 236 and 272 MeV

Cross sections for elastic scattering of ⁴⁰Ar on ⁴⁰Ca have been measured at energies E_lab = 191, 236 and 272 MeV employing position-sensitive detectors and the method of kinematical coincidences. The experimental data are first compared with the ordinary and the generalized Fresnel models. Only the generalized Fresnel model describes the experimental data well. An optical model analysis with a Woods-Saxon potential yields an energy independent set of parameters (V_R = ?21.76 MeV, r_OR = 1.37 fm, a_R = 0.45 fm; W₁ = ?13.69 MeV, r₀₁ = 1.40 fm, a₁ = 0.36 fm) very similar to the one found in ⁴⁰Ca-⁴⁰Ca scattering at corresponding energies. Values deduced for the total reaction cross sections for the three energies are in good agreement with those predicted by the generalized Fresnel model. The data are also compared with optical model calculations with the real part of the potential replaced by various microscopically determined potentials. The proximity, Fleckner-Mosel and the Krappe-Nix-Sierk potentials like the phenomenological optical model potential reproduce the measured data fairly well over several orders of magnitude.