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${{\mathit \Lambda}}$ DECAY PARAMETERS

See the ``Note on Baryon Decay Parameters'' in the neutron Listings. Some early results have been omitted.

(${{\mathit \alpha}_{{-}}}$ + ${{\mathit \alpha}_{{+}}})/({{\mathit \alpha}_{{-}}}−{{\mathit \alpha}_{{+}}}$) in ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

INSPIRE   PDGID:

S018AL

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 EVTS DOCUMENT ID TECN  COMMENT $\bf{ -0.002 \pm0.004}$ OUR AVERAGE $-0.004$ $\pm0.012$ $\pm0.009$ 73k 1 ABLIKIM 2022 AD BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Xi}}{{\overline{\mathit \Xi}}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}{{\mathit \pi}}{{\mathit \pi}}$ $-0.0025$ $\pm0.0046$ $\pm0.0012$ 3.2M ABLIKIM 2022 AG BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-0.081$ $\pm0.055$ $\pm0.059$ 8.7k ABLIKIM 2010 BES ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $+0.013$ $\pm0.022$ 96k BARNES 1996 CNTR LEAR ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \Lambda}}$ $+0.01$ $\pm0.10$ 770 TIXIER 1988 DM2 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-0.02$ $\pm0.14$ 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. • • $-0.006$ $\pm0.012$ $\pm0.007$ 420k ABLIKIM 2019 BJ BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ $-0.07$ $\pm0.09$ 4063 BARNES 1987 CNTR See BARNES 1996 1  ABLIKIM 2022AD result supersedes ABLIKIM 2019BJ. 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.

Conservation Laws:

$\mathit CP$ INVARIANCE

References:

ABLIKIM 2022AD NAT 606 64 Probing CP symmetry and weak phases with entangled double-strange baryons ABLIKIM 2022AG PRL 129 131801 Precise Measurements of Decay Parameters and $CP$ Asymmetry with Entangled $\Lambda-\bar{\Lambda}$ Pairs Pairs ABLIKIM 2019BJ NATP 15 631 Polarization and Entanglement in Baryon-Antibaryon Pair Production in Electron-Positron Annihilation ABLIKIM 2010 PR D81 012003 Measurement of the Asymmetry Parameter for the Decay ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$ BARNES 1996 PR C54 1877 Observables in High Statistics Measurements of the Reaction ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \Lambda}}$ TIXIER 1988 PL B212 523 Looking at $\mathit CP$ Invariance and Quantum Mechanics in ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$ Decay BARNES 1987 PL B199 147 CP Invariance in the Reaction ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \Lambda}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}{{\mathit p}}{{\mathit \pi}^{-}}$ at 1.546 ${\mathrm {GeV/}}\mathit c$ CHAUVAT 1985 PL 163B 273 Test of $\mathit CP$ Invariance in ${{\mathit \Lambda}}$ Decay

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