2002 Electroweak Baryon Number Violation

The conditions for baryogenesis in the early universe are well-known (cf. Refs. [1, 2]): 1. C and CP violation, 2. thermal nonequilibrium, 3. violation of baryon number conservation. How realistic are these requirements? Well, noninvariance under the charge conjugation transformation (C) and the combined charge conjugation and parity reflection transformation (CP) have been observed in the laboratory. Also, thermal nonequilibrium can perhaps be expected for certain (brief) epochs in the history of the early universe, as described by the Hot Big Bang Model. But no experiment has ever seen baryon number violation, i.e., ∆B ≡ B(tout)−B(tin) 6= 0. Strictly speaking, we know of only one physical theory that is expected to display baryon number violation: the electroweak Standard Model. The problem is, however, that the relevant processes of the Standard Model are only known at relatively low scattering energies,