Sigma Decomposition: The CP-Odd Lagrangian

Understand

In Alonso et al., JHEP 12 (2014) 034, the CP-even sector of the effective chiral Lagrangian for a generic composite Higgs model with a symmetric coset has been constructed, up to four momenta.

• In this paper, the CP-odd couplings are studied within the same context.
• If only the Standard Model bosonic sources of custodial symmetry breaking are considered, then at most six independent operators form a basis.
• One of them is the weak-$\theta$ term linked to non-perturbative sources of CP viola- tion, while the others describe CP-odd perturbative couplings between the Standard Model gauge bosons and an Higgs-like scalar belonging to the Goldstone boson sector.