Measuring CP violation in Two-Higgs-Doublet models in light of the LHC Higgs data

TL;DR

This paper investigates CP violation in Two-Higgs-Doublet models using LHC Higgs data, expressing invariants in terms of observable masses and couplings, and discusses constraints and measurement strategies.

Contribution

It provides a method to relate CP violation invariants to observable quantities and analyzes how LHC data constrains different Two-Higgs-Doublet models.

Findings

Standard-Model-like Higgs observation constrains CP violation in Z_2 symmetric models.

CP violation remains possible in the most general Two-Higgs-Doublet models.

Strategies for measuring residual CP violation are proposed.

Abstract

In Two-Higgs-Doublet models, the conditions for CP violation can be expressed in terms of invariants under U(2) rotations among the two SU(2) Higgs doublet fields. In order to design a strategy for measuring the invariants we express them in terms of observables, i.e., masses and couplings of scalar bosons. We find amplitudes directly sensitive to the invariants. Observation of the Standard-Model-like Higgs boson at the LHC severely constrains the models. In particular, in the model with Z_2 symmetry imposed on dimension-4 terms (in order to eliminate tree-level flavour-changing neutral currents), CP violation is strongly suppressed. On the other hand, the most general Two-Higgs-Doublet model (without Z_2 symmetry) would still allow for CP violation to be present in the model, without being in conflict with the LHC data. Consequently, also flavour-changing neutral currents would in general be expected. We briefly sketch a strategy for measuring the remaining CP violation.