Two-body hadronic decays of exotic quarks in E6 theories

We explore the possibility that the exotic Q=-(1/3), color-triplet, isosinglet fermion (D) present in E6 theories may have a sizable two-body hadronic decay mode Dd+g, where d is the usual down quark and g is a gluon. This process proceeds via a class of one-loop penguin-type diagrams. If the mass of the D (MD) exceeds that of the W boson, then it is easy to see that the branching ratio for the above decay is negligible. A more interesting case occurs when 23MD82 GeV, for which we find branching ratios for this process of order a few percent. This two-jet decay mode may be a clear signal for D production.