Heavy Vector-like quark with charge 5/3 at the LHC
  We study the phenomenology at the Large Hadron Collider of an exotic vector-like quark X with charge +5/3. We relax the assumption of a 100% branching into W t and allow for an arbitrary rate into W plus light quarks, thus covering all possible scenarios. Sizeable decays into light quarks can be achieved, for instance, in a model where the X quark is embedded in a doublet with hypercharge 7/6, which also contains a t' quark. We study the bounds on the parameter space of this model, and perform a detailed simulation of the X pair production and decays. We show that the final state with W t W q, where q=u or c, contributes to the same sign dilepton searches, and that the reach can be improved with alternative cuts optimised on such final state. 
Giacomo Cacciapaglia, Aldo Deandrea, Luca Panizzi, Stephane Perries,   Viola Sordini
hep-ph