Limit on CPT Violating Quark-Antiquark Mass Difference from the Neutral Kaon System

We quantify the limits on quark-antiquark mass differences imposed by the neutral kaon mass system. In particular, we find that an upper limit to the mass difference of 10 eV exists if mass differences across quark flavors are uncorrelated. We also find that such a small mass difference would be difficult to detect in upcoming antihydrogen experiments, both due to its small effect on the atomic spectrum of antihydrogen, and because of the dominant role that any electron-positron mass difference would play.