CPT violation

There are both theoretical and experimental reasons to search for CPT violations. The strong theoretical incentive is that, even though the CPT invariance is required to formulate a quantum field theory consistent with special relativity, it turns out to be difficult to construct a gravitational relativistic quantum field theory of the GUT type with the CPT symmetry maintained. In other words it is difficult to incorporate the CPT invariance in the GUT-type extensions of the Standard Model. 

As mentioned before, the low energy manifestations of CPT violation (assumed to occur at GUT energies) might be suppressed. To establish what sort of measurements have the greatest chance to discover the CPT violations a help from the theory is useful. Of course, the theoretical predictions are by necessity limited by the validity of the extensions of the Standard Model applied in the analysis. 

Similarly, the hyperfine transitions involving the spin-mixed Zeeman states within the Is level are expected to display frequency shifts due to CPT violation. In particular, the transition from the low field seeking Is — c states to the Is — d states could provide an unsupressed evidence of CPT violation that leads to differences between H and H A,h-h, -H fi... 

As an extension of QED considering only photons, electrons ( ), and muons ( ), the following CPT violating Lorentz-violating terms are added to the standard QED Lagrangian... 

The result from muonium can be compared with some other tests of CPT violation based on this theory (Table 1). Another type of experiment listed in Table 1 is the search for a time variation during a sidereal day of a nuclear magnetic resonance signal[9]. The first such experiment was done on 7Li in which the... 

However, the most stringent CPT test comes from a mass comparison of the neutral kaon and antikaon, where the tremendous accuracy of 10-18 has been reached, albeit in a theoretically dependent manner. Not only does the comparison only restrict CPT violation to 1 part in 103 of CP violation, the origin of which itself is not fully understood, but it has been argued [9] that the analysis leading to this limit assumes the validity of the standard model, which in itself does not contain a mechanism for CPT violation. 

Assuming that there is no other source of CPT violation than this mass difference, it is possible to deduce that [1]... 

CPT violation in 2tv decay. Results from CERN [1] and Fermilab [2]... 

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