Multiphoton signatures as a probe of violation in extended Higgs sectors

Abstract

We propose a novel signature with four-photon final states to probe 𝐶⁢𝑃-violating (CPV) extended Higgs sectors via 𝑓⁡ ¯ 𝑓 →𝑍*→𝐻1⁡𝐻2→4⁢𝛾 processes with 𝐻1,2 being additional neutral Higgs bosons. We focus on the nearly Higgs alignment scenario, in which the discovered Higgs boson almost corresponds to a neutral scalar state belonging to the isospin doublet field with the vacuum expectation value 𝑣≃246 GeV. We show that the branching ratios of 𝐻1,2 →𝛾⁢𝛾 can simultaneously be sizable when CPV phases in the Higgs potential are of order one due to the enhancement of charged-Higgs boson loops. Such branching ratios can be especially significant when the fermiophobic scenario is taken into account. As a simple example, we consider the general two Higgs doublet model, and demonstrate that the cross section for the four-photon process can be 0.1 fb at LHC with the masses of 𝐻1,2 to be a few 100 GeV in the Higgs alignment limit under the constraints from electric dipole moments (EDMs) and LHC Run-II data. We also illustrate that the searches for EDMs and diphoton resonances at high-luminosity LHC play complementary roles to explore CPV extended Higgs sectors.