Baryon-number violation in a quantum gas ofWand Higgs bosons

Use of a coherent-state representation of the sphaleron allows a direct calculation of its production rate in a thermal gas of W and Higgs bosons Technical considerations permit a straightforward calculation only in the case λ/${\mathrm{g}}^2$≃1 (${\mathrm{M}}_{\mathrm{H}}$≃3${\mathrm{M}}_{\mathrm{W}}$), where λ is the Higgs-boson quartic coupling, and g is the SU(2) gauge coupling. For this case it is found that the rate is unsuppressed for temperatures T≥2.4${\mathrm{M}}_{\mathrm{W}}$(0), where ${\mathrm{M}}_{\mathrm{W}}$(0) is the zero-temperature W mass. Thus anomalous B+L violation is also unsuppressed above this temperature.