Implications of a matter-antimatter mass asymmetry in Penning-trap experiments

The Standard Model (SM) of particle physics, being a local, unitary andLorentz-invariant quantum field theory, remains symmetric under the combinedaction of Charge, Parity, and Time Reversal (CPT) symmetry. This automaticallyimplies that fundamental properties of particles and antiparticles should beequal in magnitude. These fundamental tenets of the CPT principle have been putto stringent tests in recent Penning-trap experiments, where thematter-antimatter mass asymmetry has been measured. In light of these recentadvances, we compare the bounds arising on CPT invariance from kaon systemswith those from Penning-trap experiments. Using a simple yet powerful argumentof mass decomposition of hadrons, we show that bounds on quark-antiquark massdifferences from kaon oscillations are way beyond the reach of Penning-trapexperiments. We discuss possible reformulations of our understanding of the SMin the case of a discovery of CPT violation by these precision experiments. Wefind that in most cases, these extensions are quite exotic, and requiresignificant fine-tuning to preserve micro-causality.