Abstract
We study CPT and Lorentz violation in the electroweak gauge sector of the Standard Model in the context of the Standard-Model Extension (SME). In particular, we show that any non-zero value of a certain relevant Lorentz violation parameter that is thus far unbounded by experiment would imply that for sufficiently large energies one of the helicity modes of the Z boson should propagate with spacelike four-momentum and become stable against decay in vacuum. In this scenario, Cherenkov-like radiation of Z bosons by ultra-high-energy cosmic-ray protons becomes possible. We deduce a bound on the Lorentz violation parameter from the observational data on ultra-high energy cosmic rays.
Highlights
Lorentz invariance is a fundamental ingredient of both quantum field theory and GeneralRelativity
We study CPT and Lorentz violation in the electroweak gauge sector of the Standard Model in the context of the Standard-Model Extension (SME)
We show that any non-zero value of a certain relevant Lorentz violation parameter that is far unbounded by experiment would imply that for sufficiently large energies one of the helicity modes of the Z boson should propagate with spacelike four-momentum and become stable against decay in vacuum
Summary
Lorentz invariance is a fundamental ingredient of both quantum field theory and GeneralRelativity. We show that any non-zero value of a certain relevant Lorentz violation parameter that is far unbounded by experiment would imply that for sufficiently large energies one of the helicity modes of the Z boson should propagate with spacelike four-momentum and become stable against decay in vacuum. We deduce a bound on the Lorentz violation parameter from the observational data on ultra-high energy cosmic rays.
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