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${{\mathit \Sigma}}$ BARYONS
($\mathit S$ = $-1$, $\mathit I$ = 1)
${{\mathit \Sigma}^{+}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit u}}$ ${\mathit {\mathit s}}$, ${{\mathit \Sigma}^{0}}$ = ${\mathit {\mathit u}}$ ${\mathit {\mathit d}}$ ${\mathit {\mathit s}}$, ${{\mathit \Sigma}^{-}}$ = ${\mathit {\mathit d}}$ ${\mathit {\mathit d}}$ ${\mathit {\mathit s}}$

INSPIRE search

${{\mathit \Sigma}^{-}}$

$I(J^P)$ = $1(1/2^{+})$

We have omitted some results that have been superseded by later experiments. See our earlier editions.

${{\mathit \Sigma}^{-}}$ MASS

$1197.449 \pm0.030$ MeV (S = 1.2)

${\mathit m}_{{{\mathit \Sigma}^{-}}}–{\mathit m}_{{{\mathit \Sigma}^{+}}}$

$8.08 \pm0.08$ MeV (S = 1.9)

${\mathit m}_{{{\mathit \Sigma}^{-}}}–{\mathit m}_{{{\mathit \Lambda}}}$

$81.766 \pm0.030$ MeV (S = 1.2)

${{\mathit \Sigma}^{-}}$ MEAN LIFE

$(1.479 \pm0.011) \times 10^{-10}$ s (S = 1.3)

${{\mathit \Sigma}^{-}}$ MAGNETIC MOMENT

$-1.160 \pm0.025$ $\mu _{\mathit N}$ (S = 1.7)

${{\mathit \Sigma}^{-}}$ CHARGE RADIUS

$0.78 \pm0.10$ fm

${{\mathit \Sigma}^{-}}$ DECAY PARAMETERS

$\alpha _{−}$ FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \pi}^{-}}$

$-0.068 \pm0.008$

$\phi $ ANGLE FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \pi}^{-}}$ (tan$\phi $ = $\beta $ $/$ $\gamma $)

$10 \pm15$ $^\circ{}$

${\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}$ FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

$0.340 \pm0.017$

$\mathit f_{2}(0)/\mathit f_{1}$(0) FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

TRIPLE CORRELATION COEFFICIENT $\mathit D$ for ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

${\mathit g}_{{{\mathit V}}}/{\mathit g}_{{{\mathit A}}}$ FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

$0.01 \pm0.10$ (S = 1.5)

${\mathit g}_{\mathit WM}/{\mathit g}_{{{\mathit A}}}$ FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

${{\mathit \Sigma}^{-}}$ Decay Modes ▸ Expand all decays

${{\mathit n}}{{\mathit \pi}^{-}}$

$(99.848\pm{0.005})\%$

${{\mathit n}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$

$(4.6\pm{0.6})\times 10^{-4}$

${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

$(1.017\pm{0.034})\times 10^{-3}$

${{\mathit n}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{\mu}}}$

$(4.5\pm{0.4})\times 10^{-4}$

${{\mathit \Lambda}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

$(5.73\pm{0.27})\times 10^{-5}$

${{\mathit \Sigma}^{+}}{{\mathit X}}$

$<1.2\times 10^{-4}$

▸	Lepton number ($\mathit L$) violating modes

FOOTNOTES

Constrained Fit information

Except where otherwise noted, content of the 2022 Review of Particle Physics is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy), JPS and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2022. See LBNL disclaimers.