Evolution of cosmological baryon asymmetries. I. The role of gauge bosons

The time evolution of the baryon asymmetry (kn₁s) due to the interactions of a superheavy gauge boson (mass Mₗ10^15 GeV, coupling strength 145) is obtained by numerically integrating the Boltzmann equations. Particle interactions in the very early universe (t10^-35 sec) are assumed to be described by the SU (5) grand unification theory. To a good approximation the results depend upon one parameter, K2. 910^17 GeV{Mₗ}. If C and CP are not violated in the decays of the superheavy boson no asymmetry develops, and any initial baryon asymmetry is reduced by a factor of (-5. 5K). If both C and CP are violated then an initially symmetrical universe evolves a baryon asymmetry which today corresponds to kn₁s7. 810^-31+{ (16K) ^1. 3}, where 2 is the baryon excess produced when an X-X pair decays. Decays and inverse decays of superheavy bosons are primarily responsible for these results (as Weinberg and Wilczek suggested) ; however for K1 baryon production falls off much less rapidly than they had expected. A gauge boson of mass 310^14 GeV could have generated the observed asymmetry kn₁s10^-9. 81. 6 if 10^-4. 31. 6. In a companion paper the role of Higgs bosons is considered.