Zero if $\mathit CP$ is conserved; $\alpha _{−}$ and $\alpha _{+}$ are the asymmetry parameters for ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ and ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$ decay. See also the ${{\mathit \Xi}^{-}}$ for a similar test involving the decay chain ${{\mathit \Xi}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{-}}$, ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ and the corresponding antiparticle chain.

VALUE ($ 10^{-2} $) EVTS DOCUMENT ID TECN  COMMENT $\bf{ -0.1 \pm0.4}$ OUR AVERAGE $1.3$ $\pm0.7$ $\pm1.1$ 369k 1 LI 2023 C BELL ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Xi}}{{\overline{\mathit \Xi}}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}{{\mathit \pi}}{{\mathit \pi}}$ $-0.4$ $\pm1.2$ $\pm0.9$ 73k ABLIKIM 2022 AD BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Xi}}{{\overline{\mathit \Xi}}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}{{\mathit \pi}}{{\mathit \pi}}$ $-0.25$ $\pm0.46$ $\pm0.12$ 3.2M ABLIKIM 2022 AG BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-8.1$ $\pm5.5$ $\pm5.9$ 8.7k ABLIKIM 2010 BES ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $1.3$ $\pm2.2$ 96k BARNES 1996 CNTR LEAR ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \Lambda}}$ $1$ $\pm10$ 770 TIXIER 1988 DM2 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-2$ $\pm14$ 10k 2 CHAUVAT 1985 CNTR ${{\mathit p}}{{\mathit p}}$, ${{\overline{\mathit p}}}{{\mathit p}}$ ISR • • We do not use the following data for averages, fits, limits, etc. • • $-0.6$ $\pm1.2$ $\pm0.7$ 420k 3 ABLIKIM 2019 BJ BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-7$ $\pm9$ 4063 BARNES 1987 CNTR See BARNES 1996 1  LI 2023C quote the average ${{\mathit \Lambda}}$-hyperon asymmetry A${}^{\alpha }_{CP}$ from 264k ${{\mathit \Lambda}_{{{c}}}^{+}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{+}}$ decays and 105k ${{\mathit \Lambda}_{{{c}}}^{+}}$ $\rightarrow$ ${{\mathit \Sigma}^{0}}{{\mathit \pi}^{+}}$ decays, under the assumption of no $\mathit CP$ violation in the SM for ${{\mathit \Lambda}_{{{c}}}^{+}}$, i.e. $\alpha _{{{\mathit \Lambda}_{{{c}}}^{+}}}$ = $−\alpha _{{{\overline{\mathit \Lambda}}_{{{c}}}^{-}}}$. 2  CHAUVAT 1985 actually gives $\alpha _{+}({{\overline{\mathit \Lambda}}})/\alpha _{−}({{\mathit \Lambda}}$) = $-1.04$ $\pm0.29$. Assumes polarization is same in ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}$ X and ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \Lambda}}$ X. Tests of this assumption, based on $\mathit C$-invariance and fragmentation, are satisfied by the data. 3  Superseded by ABLIKIM 2022AG.

Conservation Laws:

$\mathit CP$ INVARIANCE

References