Prospect for Heavy Quarks Lighter than $M_W$

Abstract

As the excitement surrounding the heavy top quark discovery subsides, while the expectation for LEP II physics gathers, it is a good time to sit back and reflect on whether energy regions available to us have been fully explored. We emphasize that a loophole exists where heavy quarks, perhaps the actual top quark itself, could still be hidden below $M_W$. This would typically involve scalar induced decays of the heavy quark, and could be realized in models with more than one Higgs doublet, e.g. MSSM. We illustrate such mechanisms with two Higgs doublet models, the addition of singlet quarks, as well as reconsidering a fourth family of quarks and leptons. Curiously, the present $R_b$--$R_c$ problem may be a harbinger of such scenarios. Given that LEP-II would be running soon, and in view of the large amount of data that the Tevatron has collected, we urge our experimental colleagues to conduct a critical analysis.