The flavor of a light charged Higgs

The ATLAS Collaboration has recently reported a search for light-charged Higgs in t → H ⁺ b decay, with H⁺→ cb¯ . An excess with a local significance of approximately 3σ is found at mH+ ≈ 130 GeV, with a best-fit value of BR(t → H ⁺ b) × BR(H⁺→ cb¯) = (1.6 ± 0.6) × 10 ⁻³. We study the implications of such a hypothetical signal in multi-Higgs doublet models. We take into account constraints from searches for other charged Higgs decays and from flavor-changing neutral current processes. Two Higgs doublet models with flavor structure dictated by natural flavor conservation (NFC), minimal flavor violation (MFV), or the Froggatt-Nielsen (FN) mechanism cannot account for such excess. A three-Higgs doublet model with NFC can account for the signal. The Yukawa couplings of the neutral pseudoscalar A in the down sector, ŶAD , should be larger by a factor of 4 – 6 compared to the corresponding Yukawa couplings of the Higgs h, ŶhD . We further present two minimal scenarios, one in which a single Yukawa coupling in the down sector, (ŶAD)bb , gives the only significant contribution, and one in which two Yukawa couplings in the up sector, (ŶAU)tt and (ŶAU)tc , give the only significant contributions, and we discuss possible tests of these scenarios.