Backward K10 production in the reaction π−p→Λ0K+π− at 9 and 12 GeV/c

We have analysed about 85 000 fast Λ⁰ events, obtained in a fast proton triggered experiment performed at the CERN-Ω spectrometer at 9 and 12 GeV/c incident π^? beam. Nearly 2500 Λ⁰K⁺π^? events have been isolated. We find strong production of quasi-two-body processes $\text{Λ}{}^0\text{K}{}^{10}$ and $\text{∑}{}^{\mathrm{1?}}\text{K}{}^{\mathrm{+}}$ consistent with u-channel hyperon exchange. Results on Λ⁰ polarization, K¹⁰ decay parameters and differential cross sections are given for $\text{Λ}{}^0\text{K}{}^{10}\text{(892)}$ and $\text{Λ}{}^0\text{K}{}^{10}\text{(1430)}$ final states. A comparison is made with the associated backward $\text{Λ}{}^0\text{(1520)}\text{K}{}^{10}$ production seen in the four-prong reaction π^?p→pK^?K⁺π^? obtained in the same experiment.     

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.