Associated Production of CP-odd and Charged Higgs Bosons at Hadron Colliders

In the Minimal Supersymmetric Standard Model, the masses of the charged Higgs boson ($H^\pm$) and the CP-odd scalar ($A$) are related by $M_{H^+}^2=M_A^2+m_W^2$ at the Born level. Because the coupling of $W^-$-$A$-$H^+$ is fixed by gauge interaction, the Born level production rate of $q \bar q' \to W^{\pm \ast} \to A H^\pm$ depends only on one supersymmetry parameter -- the mass ($M_A^{}$) of $A$. We examine the sensitivity of the LHC to this signal event in the $A(\ra b {\bar b})H^+(\ra \tau^+ \nu_\tau)$ and $A(\ra b {\bar b})H^+(\ra t {\bar b})$ decay channels. We illustrate how to test the mass relation between $A$ and $H^+$ in case that the signal is found. If the signal is not found, the product of the decay branching ratios of $A$ and $H^\pm$ predicted by the MSSM is bounded from above as a function of $M_A$.