Two-loop corrections to the Higgs trilinear coupling in models with extended scalar sectors

TL;DR

This paper calculates the dominant two-loop corrections to the Higgs trilinear coupling in models with extended scalar sectors, showing they are smaller than one-loop effects but still potentially significant.

Contribution

It provides the first detailed analytical and numerical analysis of two-loop corrections to the Higgs trilinear coupling in extended scalar models.

Findings

Two-loop corrections are 10-20% of one-loop corrections.

Two-loop effects do not significantly alter non-decoupling effects.

Corrections remain smaller than one-loop but are not negligible.

Abstract

The Higgs trilinear coupling provides a unique opportunity to study the structure of the Higgs sector and probe indirect signs of BSM Physics -- even if new states are somehow hidden. In models with extended Higgs sectors, large deviations in the Higgs trilinear coupling can appear at one loop because of non-decoupling effects in the radiative corrections involving the additional scalar states. It is then natural to ask how two-loop corrections modify this result, and whether new large corrections can appear again. We present new results on the dominant two-loop corrections to the Higgs trilinear coupling in several models with extended scalar sectors. We illustrate the analytical expressions with numerical examples and show that, while they remain smaller than their one-loop counterparts and do not modify significantly the non-decoupling effects observed at one loop, the two-loop corrections are not entirely negligible -- a typical size being 10-20% of the one-loop corrections.