Robustness and predictivity of 4 TeV unification

The stability of the predictions of two of the standard model parameters, α3(MZ) and sin2θ(MZ), in a MU∼4 TeV unification model is examined. It is concluded that varying the unification scale between MU≃2.5 TeV and MU≃5 TeV leaves robust all predictions within reasonable bounds. Choosing MU=3.8±0.4 TeV gives, at lowest order, accurate predictions at MZ. The impact of threshold effects on unification depends on the spectrum of states beyond the standard model.