Heavy neutral 2HDM Higgs Boson Pair Production at CLIC Energies

In this work, the neutral Higgs boson pair production is analyzed at Compact Linear Collider (CLIC) to be operating at center of mass energies $\sqrt{s}$=1400 GeV (stage 2) and $\sqrt{s}$=3000 GeV (stage 3). The Higgs bosons to be searched for are neutral CP-even (H) and CP-odd (A) within the framework of two Higgs doublet model (2HDM) in the mass range 300 < mH/A < 1000 GeV. All types of the CP-conserving model are studied and the signal observability is evaluated taking into account the main SM background processes like ZZ, tt and the SM-like Higgs boson associated production (hZ). Results are presented for a set of model parameters and Higgs boson masses in terms of signal distributions over the background as well as the integrated luminosity needed for 5{\sigma} discovery. It is shown that the heavy mass region is well observable at CLIC in types 3 (flipped) and 4 (lepton-specific) in the regions not excluded by LHC so far, while in type 1 the signal observation is challenging due to the large jet multiplicity in the tt final state.