Parametrisation and dictionary for CP violating Higgs boson interactions

TL;DR

The paper tackles the fragmentation of CP-violating Higgs boson analyses across multiple theoretical formalisms by introducing a unified parametrisation and explicit dictionaries that translate between the Higgs basis, the κ-framework with CP fractions, SMEFT (Warsaw basis), and HEFT. It presents detailed mappings among these frameworks, including explicit relations for CP-odd operators, flavor assumptions, and operator redundancies, and it discusses how experimental results can be consistently interpreted within a common language. The work highlights both commonalities and unique features of each approach—such as HEFT’s additional CPV structures and the gauge-invariance constraints that link different sectors—thereby enabling robust, model-agnostic reinterpretations and facilitating global fits. By clarifying how to translate collider constraints into constraints on underlying operators, the Dictionary framework improves the reliability and comparability of CP-violation studies in the Higgs sector across current experiments and future facilities.

Abstract

Searches for charge-parity (CP) violating interactions of the Standard Model (SM) Higgs boson are a key priority of the LHC physics program. Experimental results from ATLAS and CMS are often reinterpreted within a variety of theoretical parametrisations, the most commonly used being the Higgs basis, $κ$'s and angles, CP fractions and effective field theories (EFT) such as the SMEFT and the Higgs EFT. However, differing conventions and assumptions across the literature make the translation between these parametrisations nontrivial and prone to inconsistencies. In this paper, we provide a unified framework and construct explicit dictionaries connecting these different approaches. This facilitates a transparent comparison between theoretical studies and experimental analyses, enabling more robust interpretations of CP-violating effects in Higgs boson interactions.