Conservation of $C$-Parity and $P$-parity Under what situations are $C$-Parity $C=(-1)^{L+S}$ and/or $P$-parity $P=-(-1)^L$ conserved? ( $L$ here is the relative angular momentum and S is the total intrinsic spin).
It would make sense that under EM and Strong interactions these two quantities would be conserved, since there are no inherent quark transformations. But I'm unsure about whether or not C-parity and P-parity would be conserved during weak interactions, specifically for meson decay.
 A: A basic postulate in elementary particle theories is CPT invariance.

Also the weak interaction is the only fundamental interaction that breaks parity-symmetry, and similarly, the only one to break CP-symmetry.

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The laws of nature were long thought to remain the same under mirror reflection, the reversal of one spatial axis. The results of an experiment viewed via a mirror were expected to be identical to the results of a mirror-reflected copy of the experimental apparatus. This so-called law of parity conservation was known to be respected by classical gravitation, electromagnetism and the strong interaction; it was assumed to be a universal law. However, in the mid-1950s Chen Ning Yang and Tsung-Dao Lee suggested that the weak interaction might violate this law. Chien Shiung Wu and collaborators in 1957 discovered that the weak interaction violates parity, earning Yang and Lee the 1957 Nobel Prize in Physic

Here is the fundamental experiment that showed non conservation of parity in weak interactions.

