${{\boldsymbol \Sigma}}$ BARYONS
($\boldsymbol S$ = $-1$, $\boldsymbol I$ = 1)
${{\mathit \Sigma}^{+}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit u}}$ ${\mathit {\mathit s}}$, ${{\mathit \Sigma}^{0}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit d}}$ ${\mathit {\mathit s}}$, ${{\mathit \Sigma}^{-}}$ = ${\mathit {\mathit d}}$ ${\mathit {\mathit d}}$ ${\mathit {\mathit s}}$
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${{\boldsymbol \Sigma}{(1560)}}$ Bumps $I(J^P)$ = $1(?^{?})$

This entry lists peaks reported in mass spectra around 1560 MeV without implying that they are necessarily related. DIONISI 1978B observes a 6 standard-deviation enhancement at 1553 MeV in the charged ${{\mathit \Lambda}}$ /${{\mathit \Sigma}}{{\mathit \pi}}$ mass spectra from ${{\mathit K}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ( ${{\mathit \Lambda}}$ /${{\mathit \Sigma}}$) ${{\mathit \pi}}{{\mathit K}}{{\overline{\mathit K}}}$ at 4.2 ${\mathrm {GeV/}}\mathit c$. In a CERN ISR experiment, LOCKMAN 1978 reports a narrow 6 standard-deviation enhancement at 1572 MeV in ${{\mathit \Lambda}}{{\mathit \pi}^{\pm}}$ from the reaction ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit X}}$ . These enhancements are unlikely to be associated with the ${{\mathit \Sigma}{(1580)}}$ (which has not been confirmed by several recent experiments -- see the next entry in the Listings). CARROLL 1976 observes a bump at 1550 MeV (as well as one at 1580 MeV) in the isospin-$1{}^{}{}^{}$ ${{\overline{\mathit K}}}{{\mathit N}}$ total cross section, but uncertainties in cross section measurements outside the mass range of the experiment preclude estimating its significance. See also MEADOWS 1980 for a review of this state.
${{\mathit \Sigma}{(1560)}}$ MASS (PRODUCTION EXPERIMENTS)   $\approx1560$ MeV 
${{\mathit \Sigma}{(1560)}}$ WIDTH (PRODUCTION EXPERIMENTS)
$\Gamma_{1}$ ${{\mathit \Lambda}}{{\mathit \pi}}$ seen363
$\Gamma_{2}$ ${{\mathit \Sigma}}{{\mathit \pi}}$ 304