Precision electroweak constraints on theN=3Lee-Wick standard model

Abstract

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.

Lee-Wick standard model at finite temperature

“…The oblique parameters W and Y are sensitive to the LW gauge bosons and impose Λ W = Λ B > 2.3 TeV at 95% CL [21]. Finally, the Z → bb branching fraction and forward-backward asymmetry are sensitive to the new charged scalars and impose Λ H > 640 GeV at 95% CL [26] (see also [23]). Setting each of these parameters to its lower bound, we calculate the electroweak order parameter v(T ) and find it to be indistinguishable from the solid red (i.e., innermost) curve of Fig.…”

“…In the absence of interactions, the SM particles are free, and one obtains the ideal gas term in Eq. (26). The interactions affect F by changing the energy of the multi-particle states.…”

“…partners are permitted, the allowed gauge boson partner masses must still be at least 2 TeV or higher, and the fermions may be as low as 1.5 TeV, but viable scenarios in which the scalar partners lie in the several hundred GeV range emerge [26].…”