Ioffe, B.L.; Okun, L.B.; Rudik, A.P.; The Problem of Parity Non-conservation in Weak Interaction
Zh. Eksp. Teor. Fiz. 32 (1957) 396;
JETP 5 (1957) 328;

Motivation
One of the possible theoretical explanations of the paradox of the and -decay of K-mesons (Orear, Harris, and Taylor, Phys. Rev. 102 (1956) 1676) is the hypothesis of parity non-conservation in weak interactions. Lee and Yang (Phys. Rev. 104 (1956) 254) showed that parity non-conservation in weak interactions could not have been detected by any experiments which have yet been performed (except, of course,
the K-meson decay experiments), and they proposed several experiments by which the conservation of parity could be tested. However, Yang and Lee did not require that the weak interactions be invariant under time-reversal or charge-conjugation.^{*} If one assumes that space-parity is not conserved, and that the and particles are identical, then the existence of a long-lived K^{o}-particle can
be explained by supposing either that charge-parity or time-parity is conserved. The analysis of correlation experiments by Lee and Yang assumes that time-parity is conserved and charge-parity is not conserved. We have found that, in the absence of conservation of space-parity, there exists an experimental test to decide whether charge-parity or time-parity is conserved in weak interactions. Namely, if time-parity is conserved, the long-lived (odd with respect to time-reversal) K^{o}-particle
can decay into 3 pions or into 3^{o}-mesons forming an S-state, while this process is forbidden if charge-parity is conserved. We shall show that if one assumes conservation of charge-parity one is led to results quite different from those of Lee and Yang. scriptsize ^{*} Pauli has discussed (W. Pauli, Niels Bohr and the Development of Physics, Pergamon Press, London, 1955) these problems in a general way. It is important to observe
that, when parity is not conserved, charge conjugation ceases to be equivalent to time reversal. Pauli proved that, assuming the ordinary relation between spin and statistics, the Lagrangian must be invariant under the combined operation of charge-conjugation and inversion of all four coordinates. (Extracted from the introductory part of the paper.).

Related references See also W. Pauli, Niels Bohr and the Development of Physics, Pergamon Press, London (1955);
T. D. Lee and C. N. Yang, Phys. Rev. 104 (1956) 254;
H. A. Tolhoek and S. R. de Groot, Phys. Rev. 84 (1951) 150;
Analyse data from K. Lande et al., Phys. Rev. 103 (1956) 1901;
J. Orear, G. Harris, and S. Taylor, Phys. Rev. 102 (1956) 1676;
W. F. Fry, J. Schneps, and M. S. Swami, Phys. Rev. 103 (1956) 1904;

Record comments
Indication of the possibility of charge conjugation violation in weak interactions.