Abstract:
One of the standard ways to study scenarios beyond the Standard Model involves extending the Higgs sector. This work examines the three Higgs doublet model (3HDM) in a type-Z or democratic setup, where each Higgs doublet couples exclusively to a specific type of fermion. The particle spectrum of the 3HDM includes four charged Higgs bosons, two 𝐶𝑃-odd scalars, and three 𝐶𝑃-even scalars. This work investigates the allowed mass and coupling parameter space in the type-Z 3HDM after imposing all theoretical and experimental constraints. We extract the allowed parameter space under three distinct alignment-limit conditions or mass hierarchies leveraging machine learning techniques. Specifically, we analyze scenarios where the 125 GeV Higgs is the lightest, an intermediary, or the heaviest 𝐶𝑃-even Higgs boson. Our findings indicate that while a single lighter 𝐶𝑃-even Higgs boson below 125 GeV still remains a possibility, the presence of two lighter Higgses is ruled out.