Fermiophobic light Higgs boson in the type-I two-Higgs-doublet model

The null results in the new physics searches at the LHC do not exclude a light new particle if the particle is fermiophobic. A good example is the fermiophobic Higgs boson h(f) in the type-I two-Higgs-doublet model, which occurs if we adopt alpha = pi/2 and the inverted scenario where the heavier CP-even Higgs boson is the observed one at a mass of 125 GeV. We first obtain the still-valid parameter space satisfying the theoretical requirements, flavor-changing neutral currents in B physics, the cutoff scale above 1 TeV, Higgs precision data, and the direct search bounds at high energy colliders. We also study the high energy scale behavior of the allowed parameter points via the renormalization group equation analysis. An important result is that the fermiophobic type-I can maintain the stability of the scalar potential all the way up to the Planck scale if m(hf) is larger than half the observed Higgs boson mass. Since the decay modes of h(f) -> gamma gamma, H-+/- -> h(f)W(+/-), and A -> h(f)Z are dominant, the productions of pp -> Ah(f)/H(+/-)h(f)/H(+/-)A/H+H- yield the four-photon final states at the LHC. We suggest the processes of 4 gamma / VV' (V(')=Z, W-+/-) as the discovery channels that supplement 4 gamma + V, since they have compatible cross sections and enjoy the background-free environment. (C) 2022 The Author(s). Published by Elsevier B.V.