1st generation: all of ordinary matter 2nd, 2rd generation; cosmic rays and accelerators Note: total charge in each generation = 0 2. The weak interaction Recall : + ( ) no p + e- → β-decay Problem: Coupling calculations divergent Lee, Rosenbluth and Yang (1940s); Weak boson similar to Yukawa pion, but for weak decay ‘Messenger’ role + e W- no p + e- → → Sheldon, Glashow and Weinberg (1968): gauge theory Three particles necessary to describe weak interaction ‘exchange’ W+, W-, Z0 Extremely heavy particles; integer spin (bosons) Conservation laws in weak interactions: quark flavour not conserved parity not conserved Weak neutral currents (CERN 1973) Quark or lepton absorbs neutral Z boson Detection of W and Z bosons (CERN, 1983) Z0 (UA1) e+ + e- → W+ e e+ + → W- e (UA2) e- + →
1st generation: all of ordinary matter 2nd, 2rd generation; cosmic rays and accelerators Note: total charge in each generation = 0 2. The weak interaction Recall : no → p + e- + ( β-decay ) Problem: Coupling calculations divergent Lee, Rosenbluth and Yang (1940s); Weak boson ‘Messenger’ role similar to Yukawa pion, but for weak decay no → W- → p + e- + e Sheldon, Glashow and Weinberg (1968): gauge theory Three ‘exchange’ particles necessary to describe weak interaction W+, W-, Z0 Extremely heavy particles; integer spin (bosons) Conservation laws in weak interactions: quark flavour not conserved parity not conserved Weak neutral currents (CERN 1973) Quark or lepton absorbs neutral Z boson Detection of W and Z bosons (CERN, 1983) Z0 → e+ + e- (UA1) W+ → e+ + e W- → e- + e (UA2)
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