## What is Parity

**Symmetric wave function**. Wave functions for which the value at the point (-x, -y, -z) is the same as at the point (x, y, z) are known as symmetric wave functions.**Antisymmetric wave function**. Wave functions for which the value at the point (-x, -y, -z) is minus the value as at the point (x, y, z) are known as symmetric wave functions.

A **parity transformation** (also called **parity inversion**) is the flip in the sign of *one* spatial coordinate. This is equivalent to studying the mirror image of the original system. It was originally assumed that parity must be conserved in all particle interactions, but it was demonstrated that parity does not have to be conserved in beta decay.

It had been found that the kaon, K (positive or negative), could decay in two different ways, one that produced three pions, the other only two pions. In order to account for this anomaly, Lee and Yang (physicists who were awarded the Nobel prize in 1957) postulated that parity is not conserved in processes of this type. This interaction (the decay of kaon particle) is known as the weak interaction.

Another transformation that is not conserved by the weak interaction is charge conjugation, usually symbolised by the letter C, under which all the particles in a system are replaced by their corresponding antiparticles, without making any other change.

**Nuclear and Reactor Physics:**

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- Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.
- U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.

**Advanced Reactor Physics:**

- K. O. Ott, W. A. Bezella, Introductory Nuclear Reactor Statics, American Nuclear Society, Revised edition (1989), 1989, ISBN: 0-894-48033-2.
- K. O. Ott, R. J. Neuhold, Introductory Nuclear Reactor Dynamics, American Nuclear Society, 1985, ISBN: 0-894-48029-4.
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- E. E. Lewis, W. F. Miller, Computational Methods of Neutron Transport, American Nuclear Society, 1993, ISBN: 0-894-48452-4.