Left-right symmetry and heavy particle quantum effects

We have renormalized a classical left-right model with a bidoublet, and lef t and right triplets in the Higgs sector. We focus on oblique corrections a nd show the interplay between the top quark, heavy neutrinos and Higgses co ntribution to the muon Delta r parameter. In the SM, custodial symmetry pre vents large oblique corrections to appear. Although in LR models there is n o such symmetry to make vanish the quadratically diverging terms, we have s hown 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. F rom oblique corrections they can be as large as the SM top one. Moreover, v ertex and box diagrams give additional non-decoupling effects and only conc rete numerical estimates are able to answer the question whether the model is still self-consistent. (C) 2000 Elsevier Science B.V. All rights reserve d.