Left-right symmetry and heavy particle quantum effects

TL;DR

This paper examines how heavy particles like neutrinos, Higgses, and the top quark influence electroweak precision measurements in a left-right symmetric model, highlighting the importance of non-decoupling effects.

Contribution

It provides a detailed analysis of oblique corrections in a renormalized left-right model, emphasizing the role of heavy neutrinos and Higgses in electroweak parameters.

Findings

Heavy Higgs contributions to Δr are manageable.

Heavy neutrinos can significantly impact Δr, comparable to the top quark.

Vertex and box diagrams introduce notable non-decoupling effects.

Abstract

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 $\Delta r$ 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 whether the model is still self-consistent.