Note on tree-level unitarity in the general two Higgs doublet model

Tree-level unitarity constraints on the masses of the Higgs bosons in the g eneral Two Higgs Doublet Model (THDM) are studied. We first consider the ca se where the Higgs potential is invariant under a discrete symmetry transfo rmation, and derive strong constraints on the mass of the lightest CP-even Higgs boson (M-h) as a function of tan beta. We then show that the inclusio n of the discrete symmetry breaking term weakens the mass bounds considerab ly. It is suggested that a measurement of M-h, and tan beta may enable disc rimination between the two Higgs potentials. (C) 2000 Elsevier Science B.V. All rights reserved.