Spin density matrix of baryon-antibaryon pairs in electron-positron annihilation with $P$ and $CP$ violation including electron mass

Abstract

The spin density matrix for octet baryon-antibaryon pairs produced in electron-positron annihilation is unambiguously given within the one-photon exchange in the centre-of-mass frame. Both the parity ($P$) and combined parity and charge-conjugation ($CP$) violation effects in the intermediate photon coupling to the baryon pairs are simultaneously considered. The electron mass is explicitly included in the general formulae presented in this paper. The whole framework is build upon the spin projection operator.