Higgs sector CP-violation at the electroweak phase transition

TL;DR

This work analyzes CP-violation in the MSSM Higgs sector at the electroweak phase transition by constructing a dimensionally reduced 3d effective theory for the light stop and the two Higgs doublets, including CP-violating parameters. It systematically assesses perturbative and nonperturbative contributions to CP-odd observables, especially spontaneous CP-violation, and evaluates the viability of lattice simulations to study IR effects. The findings indicate that spontaneous CP-violation is not generically realized and is confined to a small region of parameter space, which is likely in tension with experimental and transition-strength constraints, though nonperturbative effects could shift this region. The paper also outlines lattice-accessible strategies for probing CP-violation in the 3d theory and discusses implications for extensions beyond the MSSM that might enlarge the viable CP-violating parameter space.

Abstract

We consider explicit and spontaneous CP-violation related to the profile of the two Higgs doublets at the MSSM electroweak phase transition. We find, in accordance with previous results, that in principle spontaneous CP-violation could exist in the MSSM at finite temperatures, but when the constraints from experiment and the strength of the transition are taken into account, the relevant region of the parameter space is rather restricted. Nevertheless, we show that in this small region, perturbative estimates need not be reliable, and non-perturbatively the region might be slightly larger (or smaller). To allow for more precise perturbative studies and for a lattice study of the non-perturbative corrections, we construct an effective 3d theory for the light stops and the two Higgses in the regime of large mQ. The 3d theory involves CP-violating parameters and allows to determine CP-odd observables.