Analytic study of the supersymmetry-breaking scale at two loops

Summary  We study the impact of a threshold parametrized by the primordial gaugino supersymmetry-breaking mass scalem 1/2, at the two-loop level. Its contributions to sin2 θ(m Z),α GUT andM GUT are given. It is found that the inclusion of this two-loop threshold increases by ∼50% the supersymmetry-breaking scale, with respect to the case where it is ignored. All expressions are given analytically and are therefore exact. The numerical analysis is done by an iterative procedure. Note that numerical corrections, inserted by hand in order to fit the two-loop accuracy, become unnecessary.