Direct Production of Light Scalar in the Type-I Two-Higgs-Doublet Model at the Lifetime Frontier of LHC

A light pseudoscalar A in the sufficient large tanβ region of type-I two-Higgs-doublet model (2HDM) can be naturally a long-lived particle (LLP). We focus on the H±A, $HA$ and $AA$ pair productions via the electroweak processes mediated by the bosons at the LHC, including pp → W^±/Z → H±/H A and pp → h → AA at the 14 TeV LHC. The possibility of probing A as a LLP at the FASER-2, FACET, MoEDAL-MAPP-2, MATHUSLA is discussed. We find that FASER-2 fails to probe any parameter space within 0.2 GeV < mA < 10 GeV for both processes. For 130 < mH± = mH < 400 GeV, FACET, MoEDAL-MAPP-2 and MATHUSLA can probes tan β 10⁴⁻⁶ for mA 3 GeV, and tan β 10⁶⁻⁸ for 3 GeV mA < 10 GeV from pp → W^±/Z → H±/Z A processes. And pp → h → AA covers similar parameter space. All processes can surpass the current limits.