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Limits on Lorentz violation in neutral-Kaon decay

The KLOE collaboration recently reported bounds on the directional dependence of the lifetime of the short-lived neutral kaon K_S with respect to the cosmic microwave background dipole anisotropy. We interpret their results in a general framework developed to probe Lorentz violation in the weak interaction. In this approach a Lorentz-violating tensor χ_{μν} is added to the standard propagator of the W boson. We derive the K_S decay rate in a naive tree-level model and calculate the asymmetry for the lifetime. By using the KLOE data the real vector part of χ_{μν} is found to be smaller than 10^-2. We briefly discuss the theoretical challenges concerning nonleptonic decays.