Douglas S. Beder

On resonant π+p→π+pγ calculations

Abstract A current-conserving calculation of π + p→ π + p γ by using a Lagrangian (isobar) description of π p→ π p has been carried out for resonant π p kinematics. After examination of a large range of modifications of the basic description, there remains a dramatic discrepancy between theory and experiment. A recipe is given, unjustified but motivated, which gives good agreement with present data.

Absorptive contribution to πD scattering length

Abstract An unsubtracted dispertion representation is used to estimate a π D arising from two nucleon intermediate states. Because we take account of the large physical region cross section for π D → pp (due to the 3-3 resonance) our result, which differs from previous estimates, is Re a abs = +0.06 μ −1 .

Calculations of low energy πd reactions

We use the impulse approximation to calculate differential cross sections at 40 and 60 MeV (lab K.E. of π+) for the reactions π+ d → π+ d, (A), π+ d → π+ np, (B). Comparison with experiment should be useful to further our general understanding of π-nucleus processes, and we therefore encourage low-energy experiments in this unexplored area.

Process. pi. /sup 0/. -->. ee-bar. gamma. revisited

We point out that the program to extract information about the ..pi../sup 0/..gamma gamma.. form factor from the process ..pi../sup 0/..-->..ee-bar..gamma.. has so far been based on theoretical assessment exhibiting a significant omission. A secondary contributing set of amplitudes is shown not to be negligible, contrary to previous assertion. This is demonstrated in several different ways, and a start on a proper theoretical calculation of the offending amplitudes is presented.

Calculations of π+ production in nuclei

Abstract We calculate π+ production by (600 MeV) protons incident on nuclei, using a model which expresses the production rate in terms of a momentum averaged free production rate multiplied by an absorptive attenuation factor. The only free parameter is the normalization of the free NN → NNπ matrix element. This is fit to pp → pnπ+ data; subsequently absorption coefficients are calculated from this same matrix element. The results for d 2 σ d E π d Ω π agree very well with available data on nuclei.

Estimates of weak strange particle production

Motivated by the imminent operation of high-intensity “meson factories”, we estimate the rates for weak production of K and Λ at low energies, via the reactions np → Λp and πp → Kp. Our premise is dominance of the amplitudes by various “exchanges” and our typical results is dσ/dΩ ≈ 10−40 cm2/sr at 500 – 700 MeV lab k.e. of the projectile.

Suggested experimental test of CP non-invariance in Ko → π+π−γ

Abstract We look for measurable quantities in the Ko weak-electromagnetic decays which would be useful indicators of CP invariance or non-invariance and conclude that decay correlations in KL → ππγ offer the best diagnostic opportunity.