Exotic Signals of Vectorlike Quarks
  Vectorlike fermions are an important target for hadron collider searches. We show that the vectorlike quarks may predominantly decay via higher-dimensional operators into a quark plus a couple of other Standard Model fermions. Pair production of vectorlike quarks of charge 2/3 at the LHC would then lead to a variety of possible final states, including $t\bar t + 4\tau$, $t\bar b\nu + 3\tau$, $t\bar t + 4\mu$, $t\bar b\nu + 3\mu$ or $t\bar t + 4b$. Additional channels ($b\bar b + 4\tau$, $6b$, etc.) arise in the case of a vectorlike quark of charge $-1/3$. If the vectorlike quark decays into three light quarks, then the $(3j)(3j)$ signal is more difficult to observe, and the vectorlike quark mass is almost unconstrained by current searches. 
Bogdan A. Dobrescu and Felix Yu
hep-ph