Pviolating

Pviolating, often written as P-violating, refers to the property of certain physical processes that are not invariant under a parity transformation, i.e., under mirror reflection of spatial coordinates. Parity symmetry would mean that the laws of physics look the same in a mirror image; when a process changes under this reflection, it is parity-violating. The concept is central to the study of fundamental interactions in particle physics.

The first decisive demonstration came in 1956–1957 through experiments on beta decay of polarized cobalt-60, conducted by Chien-Shiung Wu and collaborators. The observed asymmetry in the emission direction of electrons relative to the nuclear spin provided clear evidence that the weak nuclear interaction does not conserve parity. This finding resolved a major puzzle and redirected understanding of the weak force as inherently chiral.

In the contemporary framework, parity violation arises from the V-A (vector minus axial-vector) structure of the weak charged current within the Standard Model. The W± bosons responsible for charged weak interactions couple preferentially to left-handed particles and right-handed antiparticles, making these interactions intrinsically asymmetric under spatial inversion. Electromagnetic and strong interactions, by contrast, are largely parity-conserving.

Parity violation has broad implications, including its connection to neutrino helicity and to the study of CP violation, which combines charge conjugation with parity and has implications for the matter–antimatter asymmetry in the universe. Ongoing experimental programs examine P-violation across various systems to test the Standard Model and probe for new physics beyond it.