Electroweak precision data and the Lee-Wick standard model

Underwood, Thomas E.J. and Zwicky, Roman (2009) Electroweak precision data and the Lee-Wick standard model. Physical Review D, 79 (3), 35016. (doi:10.1103/PhysRevD.79.035016).

Abstract

We investigate the electroweak precision constraints on the recently proposed Lee-Wick standard model at tree level. We analyze low-energy, Z-pole (LEP1/SLC) and LEP2 data separately. We derive the exact tree-level low-energy and Z-pole effective Lagrangians from both the auxiliary field and higher derivative formulation of the theory. For the LEP2 data we use the fact that the Lee-Wick standard model belongs to the class of models that assumes a so-called “universal” form which can be described by seven oblique parameters at leading order in mW2/M1,22. At tree level we find that Y=-mW2/M12 and W=-mW2/M22, where the negative sign is due to the presence of the negative norm states. All other oblique parameters (S?,X) and (T?,U?,V) are found to be zero. In the addendum we show how our results differ from previous investigations, where contact terms, which are found to be of leading order, have been neglected. The LEP1/SLC constraints are slightly stronger than LEP2 and much stronger than the low-energy ones. The LEP1/SLC results exclude gauge boson masses of M1?M2?3??TeV at the 99% confidence level. Somewhat lower masses are possible when one of the masses assumes a large value. Loop corrections to the electroweak observables are suppressed by the standard ?1/(4?)2 factor and are therefore not expected to change the constraints on M1 and M2. This assertion is most transparent from the higher derivative formulation of the theory.

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