Weak Interactions

Abstract

AbstractThe life times of elementary particles fall into three categories. First one corresponds to life times of the order of 10−23 sec, resonances like Δ1232 being a typical example. Decays of this kind are strong interaction processes in which all conservation laws like conservation of electric charge, baryon number, isospin, strangeness, and parity, are satisfied. In the second category there are few processes like π 0→2γΣ 0→Λ+γ which are electromagnetic in origin and are characterised by lifetimes of the order of 10−18 sec–10−20 sec. In the third one there are many decays with lifetimes greater than about 10−13 sec. The weak decays which include nuclear β-decay are attributed to the weak interaction. The characteristic features of such interactions are: (a) Long lifetimes (∼10−10 sec) for weak decay process. (b) Small interaction cross sections (∼10−39 cm2) via weak processes. (c) Leptons experience only weak interaction and if charged, the electromagnetic interaction as well. (d) Weak interactions do not conserve isospin. The rule is |ΔI|=1/2. (e) Weak interactions of strange particles do not conserve strangeness (Chap. 4). The rule is |ΔS|=1, for example Λ→p+π −; Ξ −→Λ+π −. (f) The weak processes do not conserve parity. KeywordsDirac EquationNeutrino OscillationCharged LeptonSolar NeutrinoWeak DecayThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.