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

INSPIRE JSON (beta) PDGID:

${{\mathit \Lambda}}$

$I(J^P)$ = $0(1/2^{+})$

We have omitted some results that have been superseded by later experiments.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

${{\mathit \Lambda}}$ MASS

$1115.683 \pm0.006$ MeV

(${\mathit m}_{{{\mathit \Lambda}}}–{\mathit m}_{{{\overline{\mathit \Lambda}}}}$) $/$ ${\mathit m}_{{{\mathit \Lambda}}}$

$(-0.1 \pm1.1) \times 10^{-5}$ (S = 1.6)

${{\mathit \Lambda}}$ MEAN LIFE

Mean life $\tau $

$(2.632 \pm0.020) \times 10^{-10}$ s (S = 1.6)

(${\mathit \tau}_{{{\mathit \Lambda}}}–{\mathit \tau}_{{{\overline{\mathit \Lambda}}}}$) $/$ ${\mathit \tau}_{{{\mathit \Lambda}}}$

$-0.001 \pm0.009$

${{\mathit \Lambda}}$ MAGNETIC MOMENT

$-0.613 \pm0.004$ $\mu _{\mathit N}$

${{\mathit \Lambda}}$ ELECTRIC DIPOLE MOMENT

$<1.5 \times 10^{-16}$ $\mathit e~$cm CL=95.0%

${{\mathit \Lambda}}$ $\mathit CP$-violating decay-rate asymmetries

$\mathit A_{CP}$( ${{\mathit p}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{\mu}}}$ ) in ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \mu}^{-}}{{\overline{\mathit \nu}}_{{\mu}}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \mu}^{+}}{{\mathit \nu}_{{\mu}}}$

${{\mathit \Lambda}}$ DECAY PARAMETERS

$\alpha _{−}$ FOR ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$

$0.748 \pm0.007$ (S = 2.1)

$\alpha _{+}$ FOR ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

$-0.757 \pm0.004$

${{\overline{\mathit \alpha}}_{{0}}}$ FOR ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit n}}}{{\mathit \pi}^{0}}$

$-0.692 \pm0.017$

$\alpha _{{{\mathit \gamma}}}$ FOR ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \gamma}}$

$-0.16 \pm0.11$

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

$-6.5 \pm3.5$ $^\circ{}$

$\alpha _{0}$ $/$ $\alpha _{−}$ = $\alpha\mathrm {( {{\mathit \Lambda}} \rightarrow {{\mathit n}} {{\mathit \pi}^{0}} )}$ $/$ $\alpha\mathrm {( {{\mathit \Lambda}} \rightarrow {{\mathit p}} {{\mathit \pi}^{-}} )}$

${{\overline{\mathit \alpha}}_{{0}}}$ $/$ ${{\mathit \alpha}_{{+}}}$ in ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit n}}}{{\mathit \pi}^{0}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

$0.913 \pm0.030$

(${{\mathit \alpha}_{{-}}}$ + ${{\mathit \alpha}_{{+}}})/({{\mathit \alpha}_{{-}}}−{{\mathit \alpha}_{{+}}}$) in ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

$-0.002 \pm0.004$

R = $\vert G_{E}/G_{M}\vert $ in ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

$\Delta \Phi $ = $\Phi _{E}$ $−$ $\Phi _{M}$ in ${{\mathit \Lambda}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}$ , ${{\overline{\mathit \Lambda}}}$ $\rightarrow$ ${{\overline{\mathit p}}}{{\mathit \pi}^{+}}$

$37 \pm13$ degrees

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

$-0.718 \pm0.015$

${{\mathit \Lambda}}$ DECAY MODES ▸ Expand all decays

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

$(64.1\pm{0.5})\%$

${{\mathit n}}{{\mathit \pi}^{0}}$

$(35.9\pm{0.5})\%$

${{\mathit n}}{{\mathit \gamma}}$

$(8.3\pm{0.7})\times 10^{-4}$

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

$(8.5\pm{1.4})\times 10^{-4}$

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

$(8.34\pm{0.14})\times 10^{-4}$

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

$(1.51\pm{0.19})\times 10^{-4}$

▸	Lepton ($\mathit L$) and/or Baryon ($\mathit B$) number violating decay modes

FOOTNOTES

Constrained Fit information

Except where otherwise noted, content of the 2023 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. © 2023. See LBNL disclaimers.