Precision Electroweak Constraints on the N=3 Lee-Wick Standard Model
  The Lee-Wick (LW) formulation of higher-derivative theories can be extended from one in which the extra degrees of freedom are represented as a single heavy, negative-norm partner for each known particle (N=2), to one in which a second, positive-norm partner appears (N=3). We explore the extent to which the presence of these additional states in a LW Standard Model affect precision electroweak observables, and find that they tend either to have a marginal effect (e.g., quark partners on T), or a substantial beneficial effect (e.g., Higgs partners on the Zbb couplings). We find that precision constraints allow LW partners to exist in broad regions of mass parameter space accessible at the LHC, making LW theories a viable beyond-Standard Model candidate. 
Richard F. Lebed and Russell H. TerBeek
hep-ph