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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   JSON  (beta) PDGID: S019

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

We have omitted some results that have been superseded by later experiments.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

${{\mathit \Sigma}^{+}}$ MASS   $1189.37 \pm0.07$ MeV (S = 2.2)

${{\mathit \Sigma}^{+}}$ MEAN LIFE   $(8.018 \pm0.026) \times 10^{-11}$ s

(${\mathit \tau}_{{{\mathit \Sigma}^{+}}}–{\mathit \tau}_{{{\overline{\mathit \Sigma}}^{-}}}$) $/$ ${\mathit \tau}_{{{\mathit \Sigma}^{+}}}$   $-0.0006 \pm0.0012$

${{\mathit \Sigma}^{+}}$ MAGNETIC MOMENT   $2.458 \pm0.010$ $\mu _{\mathit N}$ (S = 2.1)

(${\mathit \mu}_{{{\mathit \Sigma}^{+}}}$ $+$ ${\mathit \mu}_{{{\overline{\mathit \Sigma}}^{-}}}$) $/$ ${\mathit \mu}_{{{\mathit \Sigma}^{+}}}$   $0.014 \pm0.015$

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

$\alpha _{0}$ FOR ${{\mathit \Sigma}^{+}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{0}}$   $-0.982 \pm0.014$

${{\overline{\mathit \alpha}}_{{0}}}$ FOR ${{\overline{\mathit \Sigma}}^{-}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{0}}$   $0.99 \pm0.04$

(${{\mathit \alpha}_{{0}}}$ + ${{\overline{\mathit \alpha}}_{{0}}}$) $/$ (${{\mathit \alpha}_{{0}}}$ $−$ ${{\overline{\mathit \alpha}}_{{0}}}$)   $0.00 \pm0.04$

$\phi _{0}$ ANGLE FOR ${{\mathit \Sigma}^{+}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{0}}$ ($\phi _{0}$ = $\beta /\gamma $)   $36 \pm34$ $^\circ{}$

$\alpha _{+}$ $/$ $\alpha _{0}$   $-0.069 \pm0.013$

$\alpha _{+}$ FOR ${{\mathit \Sigma}^{+}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \pi}^{+}}$   $0.068 \pm0.013$

$\phi _{+}$ ANGLE FOR ${{\mathit \Sigma}^{+}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \pi}^{+}}$ ($\phi _{+}$ = $\beta /\gamma $)   $167 \pm20$ $^\circ{}$ (S = 1.1)

$\alpha _{\gamma }$ FOR ${{\mathit \Sigma}^{+}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \gamma}}$   $-0.76 \pm0.08$

Decay Modes ▸  Expand all decays
Mode   Fraction ($\Gamma_i$ / $\Gamma$) Scale Factor/ Conf. Level P(MeV/c)   $\Gamma_{1}$ ${{\mathit p}}{{\mathit \pi}^{0}}$   $(51.57\pm{0.30})\%$ 189   $\Gamma_{2}$ ${{\mathit n}}{{\mathit \pi}^{+}}$   $(48.31\pm{0.30})\%$ 185   $\Gamma_{3}$ ${{\mathit p}}{{\mathit \gamma}}$   $(1.23\pm{0.05})\times 10^{-3}$ 225   $\Gamma_{4}$ ${{\mathit n}}{{\mathit \pi}^{+}}{{\mathit \gamma}}$  [1] $(4.5\pm{0.5})\times 10^{-4}$ 185   $\Gamma_{5}$ ${{\mathit \Lambda}}{{\mathit e}^{+}}{{\mathit \nu}_{{e}}}$   $(2.0\pm{0.5})\times 10^{-5}$ 71   ▸ $\Delta \mathit S$ = $\Delta \mathit Q$ ($\mathit SQ$) violating modes or $\Delta \mathit S$ = 1 weak neutral current ($\mathit S1$) modes
FOOTNOTES

Constrained Fit information