The two-loop finite-temperature effective potential of the MSSM and baryogenesis

We construct an effective three-dimensional theory for the MSSM at high tem peratures in the Limit of large-m(A). We analyse the two-loop effective pot ential of the 3D theory for the case of a light right-handed stop to determ ine the precise region in the m(h)-m((t) over bar R) plane for which the sp haleron constraint for preservation of the baryon asymmetry is satisfied, W e also compare with results previously obtained using 3D and 4D calculation s of the effective potential. A two-stage phase transition still persists f or a small range of values of m((t) over bar R). The allowed region require s a value of m((t) over bar R) less than or similar to m(t) and m(h) less t han or similar to 100 (110) GeV for m(Q) = 300 GeV (1 TeV). (C) 1999 Elsevi er Science B.V.