0000000001230549
AUTHOR
María Belén Gavela
Standard Model CP-violation and Baryon Asymmetry. Part 2: Finite temperature
We consider the scattering of quasi-particles off the boundary created during a first order electroweak phase transition. Spatial coherence is lost due to the quasi-quark damping rate, and we show that reflection on the boundary is suppressed, even at tree-level. Simply on CP considerations, we argue against electroweak baryogenesis in the Standard Model via the charge transport mechanism. A CP asymmetry is produced in the reflection properties of quarks and antiquarks hitting the phase boundary. An effect is present at order α2W in rate and a regular GIM behaviour is found, which can be expressed in terms of two unitarity triangles. A crucial role is played by the damping rate of quasi-par…
CP nonconservation at he Z0 Peak
The measurement of a nonvanishing asymmetry α≡[Γ(sb¯)−Γ(s¯b)][Γ(sb¯)+Γ(s¯b)] would signal CP nonconservation in Z0 decays. We study here this effect within the standard model. In the three-generation case, the α value comes out small because of the effective degeneracy of u and c quarks at these high energies. In the four-generation case, results are encouraging for the CERN e+e− collider LEP: One could have a branching ratio of this flavor-changing decay to the flavor-conserving one of ∼10−6 and reach α values near unity.