The violation of parity conservation in physics refers to the discovery that certain processes in nature do not exhibit mirror symmetry, also known as parity symmetry. Parity symmetry states that the laws of physics should remain unchanged if a system is reflected in a mirror.
The experimental observation of parity violation came from studies of weak interactions, which are responsible for processes such as radioactive decay. In 1956, Chien-Shiung Wu and her colleagues conducted an experiment known as the Wu experiment, which involved measuring the distribution of emitted electrons in the beta decay of cobalt-60 nuclei. The results showed a preferential emission of electrons in a particular direction, violating the expected mirror symmetry.
The understanding of why physics is not symmetric to parity lies in the fundamental properties of the weak force and the nature of particles involved. The weak force, unlike other fundamental forces such as electromagnetism and gravity, has a distinctive feature called chirality or handedness. It means that certain particles, such as neutrinos and left-handed electrons, interact differently with the weak force compared to their mirror-reflected counterparts (right-handed neutrinos and right-handed electrons). This violation of mirror symmetry is known as the "handedness" or "chirality" of the weak interaction.
The explanation for parity violation lies within the framework of the electroweak theory, which combines the electromagnetic and weak forces into a unified theory. In this theory, the weak force is mediated by particles called W and Z bosons, which have an intrinsic chirality. The asymmetric coupling of the W and Z bosons to left-handed particles and right-handed antiparticles leads to a violation of parity symmetry.
The discovery of parity violation had profound implications for our understanding of fundamental interactions and required modifications to the prevailing theoretical framework. It highlighted the need for a more comprehensive theory, such as the electroweak theory, which successfully incorporates parity violation and provides a deeper understanding of the fundamental forces and particles in nature.