Weak Interactions and Neutrinos

Abstract

The Sun will shine for 5 billion years (after the past first 5 billion years) because of the weak interaction. The study of the weak interaction is closely connected to that of the neutral lepton called neutrino. We shall focus on: the weak interaction universality; the Feynman diagrams of charged and neutral current interactions of hadrons and leptons; the computation of the particles lifetimes, including the phase space factors; the meaning of the branching ratio; the suppression of neutral current interactions changing the strangeness quantum number and the hypothesis of the existence of the charmed quark. The theory of the weak interaction was modeled starting from that of the electromagnetic one, leading to some predictions which were confirmed by major discoveries in particle physics: the electron neutrino; the muon neutrino and lepton number conservation; the existence of weak neutral currents and that of new quark flavors; the W ^± and Z ⁰ vector bosons at CERN.