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

${{\mathit \Xi}{(1690)}}$

$I(J^P)$ = $1/2(?^{?})$ 
AUBERT 2008AK, in a study of ${{\mathit \Lambda}_{{{c}}}^{+}}$ $\rightarrow$ ${{\mathit \Xi}^{-}}{{\mathit \pi}^{+}}{{\mathit K}^{+}}$, finds some evidence that the ${{\mathit \Xi}{(1690)}}$ has $\mathit J{}^{P} = 1/2{}^{-}$. DIONISI 1978 sees a threshold enhancement in both the neutral and negatively charged ${{\mathit \Sigma}}{{\overline{\mathit K}}}$ mass spectra in ${{\mathit K}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ( ${{\mathit \Sigma}}{{\overline{\mathit K}}}$) ${{\mathit K}}{{\mathit \pi}}$ at 4.2 ${\mathrm {GeV/}}\mathit c$. The data from the ${{\mathit \Sigma}}{{\overline{\mathit K}}}$ channels alone cannot distinguish between a resonance and a large scattering length. Weaker evidence at the same mass is seen in the corresponding ${{\mathit \Lambda}}{{\overline{\mathit K}}}$ channels, and a coupled-channel analysis yields results consistent with a new ${{\mathit \Xi}}$. BIAGI 1981 sees an enhancement at 1700 MeV in the diffractively produced ${{\mathit \Lambda}}{{\mathit K}^{-}}$ system. A peak is also observed in the ${{\mathit \Lambda}}{{\overline{\mathit K}}^{0}}$ mass spectrum at 1660 MeV that is consistent with a 1720 MeV resonance decaying to ${{\mathit \Sigma}^{0}}{{\overline{\mathit K}}^{0}}$, with the ${{\mathit \gamma}}$ from the ${{\mathit \Sigma}^{0}}$ decay not detected. BIAGI 1987 provides further confirmation of this state in diffractive dissociation of ${{\mathit \Xi}^{-}}$ into ${{\mathit \Lambda}}{{\mathit K}^{-}}$. The significance claimed is 6.7 standard deviations. ADAMOVICH 1998 sees a peak of $1400$ $\pm300$ events in the ${{\mathit \Xi}^{-}}{{\mathit \pi}^{+}}$ spectrum produced by 345 GeV/$\mathit c$ ${{\mathit \Sigma}^{-}}$-nucleus interactions. SUMIHAMA 2019 observes a peak in the ${{\mathit \Xi}^{-}}{{\mathit \pi}^{+}}$ spectrum with a significance of 4.0 standard deviations.
${{\mathit \Xi}{(1690)}}$ MASSES
MIXED CHARGES   $1690 \pm10$ MeV 
${{\mathit \Xi}{(1690)}^{0}}$ MASS
${{\mathit \Xi}{(1690)}^{-}}$ MASS
${{\mathit \Xi}{(1690)}}$ WIDTHS
MIXED CHARGES   $20 \pm15$ MeV 
${{\mathit \Xi}{(1690)}^{0}}$ WIDTH
${{\mathit \Xi}{(1690)}^{-}}$ WIDTH
$\Gamma_{1}$ ${{\mathit \Lambda}}{{\overline{\mathit K}}}$   seen 240
$\Gamma_{2}$ ${{\mathit \Sigma}}{{\overline{\mathit K}}}$   seen 70
$\Gamma_{3}$ ${{\mathit \Xi}}{{\mathit \pi}}$   seen 311
$\Gamma_{4}$ ${{\mathit \Xi}^{-}}{{\mathit \pi}^{+}}{{\mathit \pi}^{0}}$   218
$\Gamma_{5}$ ${{\mathit \Xi}^{-}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$   possibly seen 213
$\Gamma_{6}$ ${{\mathit \Xi}{(1530)}}{{\mathit \pi}}$   79