Lower bound on the pseudoscalar mass in the minimal supersymmetric standard model

Abstract

In the Higgs sector of the minimal supersymmetric standard model, the mass of the pseudoscalar A is an independent parameter together with tanβ=v₂/v₁. If m_A is small, then the process e⁺e⁻ → h+A is kinematically allowed and is suppressed only if tanβ is small. On the other hand, the mass of the charged Higgs boson is now near M_W, and the decay t → b+h⁺ is enhanced if tanβ is small. Since the former has not been observed, and the branching fraction of t → b+W cannot be too small (by comparing the experimentally derived tt̅ cross section from the leptonic channels with the theoretical prediction), we can infer a phenomenological lower bound on m_A of at least 60 GeV for all values of tanβ.