What is Parity violation: Definition and 20 Discussions

In quantum mechanics, a parity transformation (also called parity inversion) is the flip in the sign of one spatial coordinate. In three dimensions, it can also refer to the simultaneous flip in the sign of all three spatial coordinates (a point reflection):














{\displaystyle \mathbf {P} :{\begin{pmatrix}x\\y\\z\end{pmatrix}}\mapsto {\begin{pmatrix}-x\\-y\\-z\end{pmatrix}}.}
It can also be thought of as a test for chirality of a physical phenomenon, in that a parity inversion transforms a phenomenon into its mirror image. All fundamental interactions of elementary particles, with the exception of the weak interaction, are symmetric under parity. The weak interaction is chiral and thus provides a means for probing chirality in physics. In interactions that are symmetric under parity, such as electromagnetism in atomic and molecular physics, parity serves as a powerful controlling principle underlying quantum transitions.
A matrix representation of P (in any number of dimensions) has determinant equal to −1, and hence is distinct from a rotation, which has a determinant equal to 1. In a two-dimensional plane, a simultaneous flip of all coordinates in sign is not a parity transformation; it is the same as a 180°-rotation.
In quantum mechanics, wave functions that are unchanged by a parity transformation are described as even functions, while those that change sign under a parity transformation are odd functions.

View More On Wikipedia.org
  1. B

    A Technical question about AMO experiment in a paper

    Hello! This is quite technical, but any advice would be greatly appreciated (@Twigg ?). It is about this paper: https://arxiv.org/pdf/1909.02650.pdf. In principle, beside the EDM, we also have spin dependent parity violating (time-reversal conserving) effects. This is always true, as we need a...
  2. W

    B Symmetry of parity: Mistake in the experiment?

    Recently I saw this YouTube video from Veritassium about CPT -Symmetry: In this video an experiment of Prof. Chien-Shiung Wu is presented, which has proven that parity is not symmetric, by observing the emmition of electrons from Co60 atoms with synchronised spin. After thinking about this...
  3. M

    I How can I prove the parity violation potential in a P,T-symmetric system?

    Hello! I read in several papers (e.g. this one) that if we have 2 levels of fixed, opposite parities, which are the eigenstates of a P,T-even Hamiltonian, and we add a perturbing potential which is P-odd, T-even, the matrix element of the new potential between the 2 states of opposite parity...
  4. M

    I Why Is Octupole Deformation Measurable in Nuclei but Not Dipole Deformation?

    Hello! I don't know much about this, so maybe the answer to my questions follows directly from the math of it, but I was wondering if there is an answer providing more physics intuition to this, not just math: Why can a nucleus have an octupole deformation, as a ground state stationary state...
  5. F

    A Madame Wu Experiment: Doubts & Reasoning

    Hi all, I have some doubts regarding the experiment of Madame Wu. I know a strong magnetic field is used to polarise the ##^{60}Co## nuclei, then we have an anthracene scintillator on the top of the sample which will detect the electron produced in the decay: ##^{60}Co \rightarrow...
  6. V

    Parity violation in lambda baryon decay

    Homework Statement In the weak decay of the lambda baryon to a proton and pion, parity is not conserved, allowing for s and p waves in the orbital wave function of the pion-proton system. Using non-relativistic wavefunctions, find the angular distribution of the protons relative to the...
  7. MaxFieg

    I Wu Experiment and Parity Violation

    I have a question concerning the nature of Ms. Wu's experiment confirming parity violation. I'm very familiar with this experiment and its outcomes, but the setup of the experiment itself, alludes me. Wu found that the electron's emitted from the Cobalt-60 atom always went in the direction...
  8. T

    Parity violation on macroscopic scale

    a question which is bugging me... Yes, I know that parity is violated only by the Weak Interaction, which is very short range. So I would answer "no, there is no P violation on macroscopic scale" However, many macroscopic properties are the results of what happens on the microscopic level. So...
  9. J

    Parity violation in weak decays

    I am confused about when and to what extent parity is violated in weak decays. On the one hand, there's Wu's famous experiment where electrons are emitted preferentially in one direction. This parity violation can be said to be maximal, since all electrons are emitted in one direction...
  10. J

    Parity violation in weak decays

    Homework Statement I am confused about parity violation in weak decays. I learned about Wu's famous experiment and how it demonstrates that parity is violated in weak decays. However, when I am doing a course problem on nuclear β-decay, then it still necessary to conserve parity...
  11. S

    Parity Violation in Weak Decay

    I just came across the following Quote in an introductory Quantum physics book"There are certain experiments in which behave differently in their mirror image form, this is called the Parity Violation in." Can anybody explain in detail what parity violation is and what mathematical description...
  12. K

    [noob] simple parity violation

    hi, I'm studying parity violation in particle physics.. I have this decay: 1+ ---> 0+ + 0+ in J^P notation. Why this process violate parity? All terms have positive parity. The parity of the products is just (+1)*(+1)*(-1)^l, so this means that the two scalar particles...
  13. Z

    What is the relationship between spin and parity in particle interactions?

    Can someone explain in easy to understand terms, what parity violation is? specifically: "Only the left-handed components of particles and right-handed components of antiparticles participate in weak interactions in the standard model." Thanks in advance.BONUS: if you're like a particle...
  14. M

    Parity Violation of Weak Force - Wu et al.

    I have read about Wu et al. and their experiments with Co 60 that showed that the weak interaction violates parity. I don't quite get it tho. 6 So they aligned Co atoms in a magnetic field. Some of the nuclei decay and emit neutrinos and electrons. It was observed that an equal number of the...
  15. M

    Definition of 'good quantum number' after parity violation

    Hi folks. I was always under the impression that the 'good quantum numbers' that we use to classify a particle species were always the eigenvalues of operators that commute with Hamiltonian governing that species. But it just struck me that weakly interacting particles have definite parity...
  16. bcrowell

    Incorrect explanation of parity violation?

    This APS page http://focus.aps.org/story/v22/st19 describes the classic experiment by Wu et al. in the 50's that demonstrated parity violation. It contains the following explanation: "[1] The magnetism of the nuclei can be thought of as resulting from their spin. With the nuclei aligned with...
  17. J

    Confusion over parity violation

    I'm trying to get my head around the cobalt-60 beta decay experiment that apparently was used to show the weak decay did not conserve parity. It basically has a bunch of cobalt nuclei at low temperature in a magnetic field so that their spins are all aligned parallel to the field. The experiment...
  18. S

    Helicity, Chirality, and Parity Violation

    Hello all, This is something that has irked me for a while. The Li/Yang/Wu beta decay showed parity violation in the weak force, but from what I gather, it was the helicities of the electrons they measured, while it is the chiral states which are important. For a massive fermion, aren't the...
  19. G

    Cobalt 60 and parity violation

    I'm considering the beta decay of a neutron into a proton an electron and an antineutrino. I heard that this was observed in 1957 in Cobalt 60. I don't really understand when the antineutrino comes into action... The experimental results say that they detected more electrons in the direction...
  20. C

    Parity violation with respect to massive neutrinos

    Now that it is becoming apparent that neutrinos are massive (albeit rather small), I have a question that bears upon the accepted symmetry framework as applied to weak interacton. We know from weak decay (say Beta) that there is parity asymmetry, that the resultant neutrinos are polarized...