Tests of fundamental symmetries with decay

Since the fall of parity in electroweak interactions the discrete transformations of parity, charge conjugation and time reversal are under close scrutiny for any sign of deviation from maximality where symmetry breaking seems to be complete (like P violation in decay) and for any sign of symmetry breaking when this has not yet been observed (like T violation in decay). The Standard Model (SM) of electroweak interactions remains robust in explaining the outcome of all experiments with rays. Bounds set by P- and T-reversal tests are tightening but remain stubbornly within the SM. However, the solar-neutrino issue enters the era beyond the SM by requiring oscillations and a non-zero mass. This review emphasizes experiments with rays, but includes solar-neutrino and -decay findings and devotes some attention to the broken symmetry in biochirality. Theoretical descriptions attempt to implement the symmetry breaking in a causal way, pointing to a possible earlier manifest left - right symmetry, and stimulating searches for deviations from the above maximality as a `fossil' remnant of symmetry at a deeper level.