Modern Physics Letters A, ❢c World Scientific Publishing Company CPT – and B–VIOLATION: THE p − p SECTOR ∗

The CP T symmetry of relativistic quantum field theory requires the total lifetimes of particles and antiparticles be equal. Detection of p lifetime shorter than τp ∼ > O(10 32) yr would signal breakdown of CP T invariance, in combination with B–violation. The best current limit on τ p , inferred from cosmic ray measurements, is about one Myr, placing lower limits on CP T –violating scales that depend on the exact mechanism. Paths to CP T breakdown within and outside ordinary quantum mechanics are sketched. Many of the limiting CP T –violating scales in p decay lie within the weak–to–Planck range. The CP T symmetry of local relativistic quantum field theory (LRQFT) has been tested in a number of elementary systems, in some cases to great accuracy. 1,2,3 CP T conservation rests on Lorentz invariance, locality, microcausality, and uniqueness of the vacuum. 4 With no obvious evidence to the contrary, we assume CP T symmetry to be good. But, as in the case of other discrete symmetries, the search for small, non-vanishing exceptions is important in its own right and as a check for residual forces outside the Standard Model. CP T symmetry requires that the properties of matter and antimatter particles (charge, mass, magnetic moment) be related by charge conjugation. Less precise tests of CP T have also been conducted with other systems: 5,6 here the comparison of the proton and antiproton decay lifetimes, τ p and τ p , is presented. The masses and electromagnetic properties of p and p are still assumed identical for simplicity and charge (Q) conservation unbroken. This test of CP T invariance is the first to be directly combined with baryon number (B) violation. Such properties as intrinsic decay lifetimes cannot be limited with artificially produced antimatter at a level remotely approaching that possible with matter, as * Based on a contribution to the CP T and Lorentz Symmetry Meeting