Invariant approach to CPCP in unbroken Δ(27)Δ(27)

The invariant approach is a powerful method for studying CPCP violation for specific Lagrangians. The method is particularly useful for dealing with discrete family symmetries. We focus on the CPCP properties of unbroken Δ(27)Δ(27) invariant Lagrangians with Yukawa-like terms, which proves to be a rich framework, with distinct aspects of CPCP, making it an ideal group to investigate with the invariant approach. We classify Lagrangians depending on the number of fields transforming as irreducible triplet representations of Δ(27)Δ(27). For each case, we construct CPCP-odd weak basis invariants and use them to discuss the respective CPCP properties. We find that CPCP violation is sensitive to the number and type of Δ(27)Δ(27) representations.