Volkard Linke

LEPTONIC DECAYS OF BARYONS

Formulae are obtained for the differential decay rate, lepton spectrum, and partial lifetime for the leptonic decays of baryons, which cover effects down to the order of one percent. A weak, linearq2-dependence of the form factors is included, which should be a sufficiently good approximation in the physicalq2-range allowed in the decays. The one percent discrepancy arises as a consequence of the above-mentioned approximation to the form factors, whose value and slope atq2=0 are left open in the formulae;SU(3) symmetry, CVC, and PCAC yield an estimate for these parameters.

Leptonic decays of polarized baryons (II)

Abstract For the weak electronic decay of a polarized hyperon formulae are given, which express explicitly the various energy-dependent asymmetry coefficients in the angular distribution of the decay products in terms of the weak form factors.

Determination of the Σ± → Λe±ν decay parameters

From about 6×106 stoppingK−-meson reactions in the Saclay 80 cm hydrogen bubble chamber 70Σ−→Λe−¯ν and 11Σ+→Λe+ν decays have been identified. The ratio of the vector to axial vector coupling constant has been determined,f1/g1=−0.22±0.28, consistent with the predictionf1=0 of the CVC-theory. The branching ratios for the two decay modes are,Γ(Σ−→Λe−ν)/Γ(Σ−→ all modes)=(0.69±0.12). 10−4,Γ(Σ+→Λe+ν)/Γ(Σ+→ all modes)=(0.29±0.10). 10−4. The ratio, Γ(Σ+→Λe+)/Γ(Σ−→Λe−v)=0.69±0.18, agrees with the phase space ratio, 0.61, therefore a theory that includes no second class currents is consistent with the data.

First and second class weak hadronic currents and their implications for Kl3 decays in an extended Cabibbo model

Within the framework of a generalized Cabibbo model for the weak hadronic current in which the current is allowed to transform like an arbitrary mixture of SU(3) multiplets, thus accomodating possible ΔS = −ΔQ, ΔS = 2, and ΔI = 32 transitions, the concept of a first and second class strangeness non-changing, CP conserving current is extended to the strangeness changing, CP violating case. Using the experimental information on the branching ratio Γ (K− → π0e−ν)/Γ(KL → π+e−ν), predictions are made for the quantity (1−|x|2)/|1−x|2, where x ≡ A(K0 → π+e−ν/ A(K0 → π+e−ν) and the decay ratio Γ(η → π+e−ν)/ Γ(π− → π0e−ν) assuming that the current is either first or second class. It is found that a first class current leads to predictions which are in good agreement with experiment.

Prediction of Re ɛ fromK13 decays in an extended cabibbo model

With the help of an extended Cabibbo model for the weak hadronic vector current which includes the 10 and ¯10 representations to account for possibleΔS=-ΔQ transitions, a prediction is made for the quantity (1-¦x¦2)/¦1−x¦2 wherex=A(K0→πüe−¯v)/A(¯K0→πüe−¯v) using the experimental branching ratio Γ(K−→ π0e−¯v/Γ(KL0→πüe−¯v). From the known charge asymmetry in the decay of the long lived kaon one then obtains Reɛ.

Study of angular decay correlations for the process π+ N →ϱ+ N * in the regge-pole model-II

A theoretical model is presented to describe the angular correlations and differential cross-section for the reaction π+N→ϱ+N*, where the ρ andN* decay into two pions, and into pion+nucleon, respectively. For the production mechanism a Regge-pole model is assumed involving the exchange of the π and A2 trajectories; while the A2 is fully Reggeized, arguments are presented in favour of treating the pion essentially as elementary. Assuming that thet-dependence of the residue functions is given by the kinematic singularities and zeros, together with an exponential behaviour which is independent of the helicities, the number of parameters required can be reduced to seven. For the purpose of the experimental analysis (which will be carried out in a subsequent paper) a list of projection functions is given, with the help of which the various coefficients multiplying the angular functions describing the decay distribution may be obtained.