Constraints on light scalars in the Aligned-two-Higgs-doublet model

Abstract

In this work, we explore the viability of light-scalar scenarios within the $\mathcal{C}\mathcal{P}$-conserving, flavour-aligned two-Higgs-doublet model (A2HDM), where at least one additional neutral or charged scalar is assumed to be lighter than the 125 GeV Higgs boson. The A2HDM naturally avoids flavour-changing neutral currents via Yukawa alignment, providing a more flexible framework than conventional $Z_2$-symmetric models. Employing the $\text{HEPfit}$ package within a Bayesian statistical approach, we perform global fits across all distinct light-scalar configurations, incorporating theoretical requirements and experimental constraints from electroweak precision observables, flavour data, Higgs measurements, and direct searches at the LEP and the LHC.

Contribution to the 2025 Electroweak session of the 59th Rencontres de Moriond