${{\boldsymbol \Lambda}}$ DECAY PARAMETERS

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

($\alpha $ + $\bar\alpha)/(\alpha −\bar\alpha$) in ${{\boldsymbol \Lambda}}$ $\rightarrow$ ${{\boldsymbol p}}{{\boldsymbol \pi}^{-}}$ , ${{\overline{\boldsymbol \Lambda}}}$ $\rightarrow$ ${{\overline{\boldsymbol p}}}{{\boldsymbol \pi}^{+}}$ INSPIRE search

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
$\bf{ -0.002 \pm0.012}$ OUR AVERAGE
$-0.006$ $\pm0.012$ $\pm0.007$ 420k
ABLIKIM
2019BJ
BES3 ${{\mathit J / \psi}}$ to ${{\mathit \Lambda}}{{\overline{\mathit \Lambda}}}$
$-0.081$ $\pm0.055$ $\pm0.059$ $\approx{}$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 1
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. • • •
$-0.07$ $\pm0.09$ 4063
BARNES
1987
CNTR See BARNES 1996
1  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 2019BJ
NATP 15 631
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