Left-right symmetry and heavy particle quantum effects

We have renormalized a classical left-right model with a bidoublet, and left and right triplets in the Higgs sector. We focus on oblique corrections and show the interplay between the top quark, heavy neutrinos and Higgses contribution to the muon Delta r parameter. In the SM, custodial symmetry prevents large oblique corrections to appear. Although in LR models there is no such symmetry to make vanish the quadratically diverging terms, we have shown that heavy Higgses contributions to dr are under control. Also the top contribution to Delta r, quite different from that in the SM, is discussed. However, heavy neutrinos seem to give the most important contributions. From oblique corrections they can be as large as the SM top one. Moreover, vertex and box diagrams give additional non-decoupling effects and only concrete numerical estimates are able to answer the question whether the model is still self-consistent. (C) 2000 Elsevier Science B.V. All rights reserved.