The complex 2HDM (C2HDM) is the most general CP-violating two Higgs-doublet-model that possesses a softly broken Z2 symmetry. However, the physical consequences of the model cannot depend on the basis of scalar fields used to define it. Thus, to get a better sense of the significance of the C2HDM parameters, we have analyzed this model by employing a basis-independent formalism. This formalism involves transforming to the Higgs basis (which is defined up to an arbitrary complex phase) and identifying quantities that are invariant with respect to this phase degree of freedom. Using this method, we have obtained the constraints that enforce the softly broken Z2 symmetry. One can then relate the C2HDM parameters to basis-independent quantities up to a twofold ambiguity. We then show how this remaining ambiguity is resolved. We also examine the possibility of spontaneous CP violation when the scalar potential of the C2HDM is explicitly CP conserving. Basis-independent constraints are presented that govern the presence of spontaneous CP violation.
Physical Review D
- Pub Date:
- March 2020
- High Energy Physics - Phenomenology
- 65 pages, 3 tables. Appendix E added to version 2, additional references included, and a number of clarifications (and corrections of typographical errors) implemented. A few more references and a number of clarifying footnotes added in version 3 (title change dictated by Physical Review D). Version 4 matches the published version