in e + e − → t ¯ bH − production at future Linear Colliders

Heavy charged Higgs bosons (H) of a Type II 2-Higgs Doublet Model (2HDM) can be detected at future electron-positron Linear Colliders (LCs) even when their mass is larger than half the collider energy. The single Higgs mode ee → tb̄H+ c.c. → 4b+jj+ l+p T (where j represents a jet and with l = e, μ) contributes to extend the discovery reach of H states into the mass region MH± ∼ √ s/2, where the well studied pair production channel ee → HH is no longer available. With a technique that allows one to reconstruct the neutrino four-momentum in the decay t → bW → blν, one can suppress the main irreducible background due to ee → tt̄bb̄ (via a gluon splitting into bb̄ pairs) to a negligible level. We prove that one can establish a statistically significant H signal over a region of several tens of GeV beyond MH± ≈ √ s/2, as long as tanβ ∼ 30.