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${{\mathit \Xi}}$ BARYONS ($\mathit S$ = $-2$, $\mathit I$ = 1/2) ${{\mathit \Xi}^{0}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit s}}$ ${\mathit {\mathit s}}$, ${{\mathit \Xi}^{-}}$ = ${\mathit {\mathit d}}$ ${\mathit {\mathit s}}$ ${\mathit {\mathit s}}$

INSPIRE   JSON PDGID: S022

${{\mathit \Xi}^{-}}$ $I(J^P)$ = $1/2(1/2^{+})$

The parity has not actually been measured, but ${}^{}{}^{+}$ is of course expected. We have omitted some results that have been superseded by later experiments. See our earlier editions.

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${{\mathit \Xi}^{-}}$ MASS $1321.70$ $\pm0.09$ MeV

${{\overline{\mathit \Xi}}^{+}}$ MASS $1321.71$ $\pm0.07$ MeV

(${\mathit m}_{{{\mathit \Xi}^{-}}}-{\mathit m}_{{{\overline{\mathit \Xi}}^{+}}}$) / ${\mathit m}_{{{\mathit \Xi}^{-}}}$ ($-3$ $\pm9$) $ \times 10^{-5}$

${{\mathit \Xi}^{-}}$ MEAN LIFE ($1.639$ $\pm0.015$) $ \times 10^{-10}$ s

${{\overline{\mathit \Xi}}^{+}}$ MEAN LIFE ($1.70$ $\pm0.14$) $ \times 10^{-10}$ s

(${\mathit \tau}_{{{\mathit \Xi}^{-}}}-{\mathit \tau}_{{{\overline{\mathit \Xi}}^{+}}}$) / ${\mathit \tau}_{{{\mathit \Xi}^{-}}}$ $-0.01$ $\pm0.07$

${{\mathit \Xi}^{-}}$ MAGNETIC MOMENT $-0.6507$ $\pm0.0025$ $\mu _{\mathit N}$

${{\overline{\mathit \Xi}}^{+}}$ MAGNETIC MOMENT $0.657$ $\pm0.034$ $\mu _{\mathit N}$

(${\mathit \mu}_{{{\mathit \Xi}^{-}}}$ + ${\mathit \mu}_{{{\overline{\mathit \Xi}}^{+}}}$) / $\vert {\mathit \mu}_{{{\mathit \Xi}^{-}}}\vert $ $+0.01$ $\pm0.05$

▸  exp ${{\mathit \Xi}}$ DECAY PARAMETERS

$\alpha\mathrm {({{\mathit \Xi}^{-}})}{}\alpha _{−}({{\mathit \Lambda}}$) $-0.288$ $\pm0.005$  (S = 2.2)

$\alpha ({{\mathit \Xi}^{-}}$) for ${{\mathit \Xi}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{-}}$ $-0.367^{+0.005}_{-0.006}$

${{\overline{\mathit \alpha}}}({{\overline{\mathit \Xi}}^{+}}$) for ${{\overline{\mathit \Xi}}^{+}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \pi}^{+}}$ $0.374^{+0.005}_{-0.006}$

($\alpha $ + ${{\overline{\mathit \alpha}}}$) / ($\alpha $ $−$ ${{\overline{\mathit \alpha}}}$) for ${{\mathit \Xi}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{-}}$, ${{\overline{\mathit \Xi}}^{+}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \pi}^{+}}$ $-0.009^{+0.011}_{-0.008}$

${[\alpha\mathrm {({{\mathit \Xi}^{-}})}\alpha_-({{\mathit \Lambda}}) − {{\overline{\mathit \alpha}}}{{{\overline{\mathit \Xi}}^{+}}}\alpha_+({{\overline{\mathit \Lambda}}})]\over [\alpha\mathrm {({{\mathit \Xi}^{-}})}\alpha_-({{\mathit \Lambda}}) + {{\overline{\mathit \alpha}}}{{{\overline{\mathit \Xi}}^{+}}}\alpha_+({{\overline{\mathit \Lambda}}})]}$ $0.0000$ $\pm0.0007$

$\phi _{-}$ ANGLE FOR ${{\mathit \Xi}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{-}}$ (tan$\phi $ = $\beta /\gamma $) $-1.5$ $\pm0.6$ $^\circ{}$

$\phi _{+}$ ANGLE FOR ${{\overline{\mathit \Xi}}^{+}}$ $\rightarrow$ ${{\overline{\mathit \Lambda}}}{{\mathit \pi}^{+}}$ (tan$\phi $ = $\beta /\gamma $) $0.6^{+0.7}_{-1.0}$ $^\circ{}$

$\Delta \phi _{CP}$ = ($\phi _{-}$+ $\phi _{+}$)/2 $-0.2^{+0.5}_{-0.6}$ $^\circ{}$

${\mathit g}_{{{\mathit A}}}$ / ${\mathit g}_{{{\mathit V}}}$ FOR ${{\mathit \Xi}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ [1] $-0.25$ $\pm0.05$

${{\mathit \Xi}^{-}}$ DECAY MODES

Mode   Fraction ($\Gamma_i$ / $\Gamma$) Scale Factor/ Conf. Level P(MeV/c)   $\Gamma_{1}$ ${{\mathit \Lambda}}{{\mathit \pi}^{-}}$ ($99.887$ $\pm0.035$ ) $\%$ 140   $\Gamma_{2}$ ${{\mathit \Sigma}^{-}}{{\mathit \gamma}}$ ($1.27$ $\pm0.23$) $ \times 10^{-4}$ 118   $\Gamma_{3}$ ${{\mathit \Lambda}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ ($5.63$ $\pm0.31$) $ \times 10^{-4}$ 190   $\Gamma_{4}$ ${{\mathit \Lambda}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{{\mu}}}}$ ($3.5^{+3.5}_{-2.2}$) $ \times 10^{-4}$ 163   $\Gamma_{5}$ ${{\mathit \Sigma}^{0}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ ($8.7$ $\pm1.7$) $ \times 10^{-5}$ 123   $\Gamma_{6}$ ${{\mathit \Sigma}^{0}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{{\mu}}}}$ $<8$ $\times 10^{-4}$ CL=90% 70   $\Gamma_{7}$ ${{\mathit \Xi}^{0}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ $<2.59$ $\times 10^{-4}$ CL=90% 7   ▸  exp $\Delta \mathit S$ = 2 forbidden ($\mathit S2$) modes $\Gamma_{8}$ ${{\mathit n}}{{\mathit \pi}^{-}}$ S2 $<1.9$ $\times 10^{-5}$ CL=90% 304   $\Gamma_{9}$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ S2 $<3.2$ $\times 10^{-3}$ CL=90% 327   $\Gamma_{10}$ ${{\mathit n}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{{\mu}}}}$ S2 <1.5 $\%$ CL=90% 314   $\Gamma_{11}$ ${{\mathit p}}{{\mathit \pi}^{-}}{{\mathit \pi}^{-}}$ S2 $<4$ $\times 10^{-4}$ CL=90% 223   $\Gamma_{12}$ ${{\mathit p}}{{\mathit \pi}^{-}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{{e}}}}$ S2 $<4$ $\times 10^{-4}$ CL=90% 305   $\Gamma_{13}$ ${{\mathit p}}{{\mathit \pi}^{-}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{{\mu}}}}$ S2 $<4$ $\times 10^{-4}$ CL=90% 251   $\Gamma_{14}$ ${{\mathit p}}{{\mathit \mu}^{-}}{{\mathit \mu}^{-}}$ L $<4$ $\times 10^{-8}$ CL=90% 272

[1] The parameters ${\mathit g}_{{{\mathit A}}}$, ${\mathit g}_{{{\mathit V}}}$, and ${\mathit g}_{\mathit WM}$ for semileptonic modes are defined by ${{\overline{\mathit B}}_{{{f}}}}[{{\mathit \gamma}_{{{\lambda}}}}({\mathit g}_{{{\mathit V}}}$ $+$ ${\mathit g}_{{{\mathit A}}}{{\mathit \gamma}_{{{5}}}}$) $+$ $\mathit i({\mathit g}_{\mathit WM}/{\mathit m}_{{{\mathit B}_{{{i}}}}}$) $\sigma _{\lambda \nu }$ $\mathit q{}^{\nu }]\mathit B_{\mathit i}$, and $\phi _{\mathit AV}$ is defined by ${\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}$ = $\vert {\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}\vert \mathit e{}^{\mathit i\phi _{\mathit AV}}$. See the ``Note on Baryon Decay Parameters'' in the neutron Particle Listings.

Constrained Fit information