Trying to Catch the Elusive $a^0$ and More. Reactions Initiated by $b$--Quarks the Higgs Sector of ${\cal MSSM}$

We study the cross sections for the production of a neutral, intermediate mass Higgs boson in the processes $pp\rightarrow tq'\Phi$, $pp\rightarrow tW^-\Phi$ and $pp\rightarrow bZ^0\Phi$ in the Minimal Supersymmetric Standard Model ($\Phi=H^0,h^0$ and $A^0$) at Supercollider energies. The additional heavy particles ($t$, $W$, $Z$) in the final state can be used for tagging purposes, increasing the signal to background ratio. These reactions are dominated by $bq$ and $bg$ fusion. Their relevance for Higgs particle searches is discussed taking into account the expected efficiencies and purities for $b$--tagging. We find that, for tan$\beta = 30$, the cross sections for $pp\rightarrow bZ^0\Phi$ are larger than 14 $pb$, over the whole intemediate range of $M_{A^0}$, for $A^0$ and at least one of the other two Higgses. Therefore this reaction is an excellent candidate for the discovery of one or more $\cal MSSM$ Higgs particles.}