STRANGE MESONS
($\mathit S$ = $\pm1$, $\mathit C$ = $\mathit B$ = 0)
${{\mathit K}^{+}}$ = ${\mathit {\mathit u}}$ ${\mathit {\overline{\mathit s}}}$, ${{\mathit K}^{0}}$ = ${\mathit {\mathit d}}$ ${\mathit {\overline{\mathit s}}}$, ${{\overline{\mathit K}}^{0}}$ = ${\mathit {\overline{\mathit d}}}$ ${\mathit {\mathit s}}$, ${{\mathit K}^{-}}$ = ${\mathit {\overline{\mathit u}}}$ ${\mathit {\mathit s}}$, similarly for ${{\mathit K}^{*}}$'s 		INSPIRE   JSON PDGID:
S010

${{\mathit K}^{\pm}}$

$I(J^P)$ = $1/2(0^{-})$ 
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${{\mathit K}^{\pm}}$ MASS [1] $493.677$ $\pm0.013$ MeV (S = 2.4)
 
${\mathit m}_{{{\mathit K}^{+}}}-{\mathit m}_{{{\mathit K}^{-}}}$ $-0.03$ $\pm0.09$ MeV 
 
${{\mathit K}^{\pm}}$ MEAN LIFE ($1.2379$ $\pm0.0021$) $ \times 10^{-8}$ s (S = 1.9)
 
$({\mathit \tau}_{{{\mathit K}^{+}}}-{\mathit \tau}_{{{\mathit K}^{-}}})/{\mathit \tau}_{\mathrm {average}}$ ($1.0$ $\pm0.9$) $ \times 10^{-3}$  (S = 1.2)
 
▸  $\mathit CPT$ VIOLATION TESTS IN ${{\mathit K}^{\pm}}$ DECAYS
▸  $\mathit CP$ VIOLATION TESTS IN ${{\mathit K}^{\pm}}$ DECAYS
▸  $\mathit T$ VIOLATION TESTS IN ${{\mathit K}^{+}}$ AND ${{\mathit K}^{-}}$ DECAYS
▸  ENERGY DEPENDENCE OF ${{\mathit K}^{\pm}}$ DALITZ PLOT
▸  ALTERNATIVE PARAMETRIZATIONS OF ${{\mathit K}^{\pm}}$ $\rightarrow$ ${{\mathit \pi}^{\pm}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ DALITZ PLOT
▸  ${{\mathit K}_{{{{{\mathit \ell}}3}}}^{\pm}}$ FORM FACTORS
▸  ${{\mathit K}_{{{{{\mathit \ell}}4}}}^{\pm}}$ FORM FACTORS
▸  ${{\mathit K}^{\pm}}$ $\rightarrow$ ${{\mathit \ell}^{\pm}}{{\mathit \nu}}{{\mathit \gamma}}$ FORM FACTORS
${{\mathit K}^{\pm}}$ CHARGE RADIUS $0.560$ $\pm0.031$ fm 
 
${{\mathit K}^{+}}$ LONGITUDINAL POLARIZATION OF EMITTED ${{\mathit \mu}^{+}}$ <-0.990   CL=90%
 
▸  FORWARD-BACKWARD ASYMMETRY IN ${{\mathit K}^{\pm}}$ DECAYS
${{\mathit K}^{-}}$ modes are charge conjugates of the modes below.
Mode  
Fraction ($\Gamma_i$ / $\Gamma$) Scale Factor/
Conf. Level		 P(MeV/c)  
▸  Leptonic and semileptonic modes
▸  Hadronic modes
▸  Leptonic and semileptonic modes with photons
▸  Hadronic modes with photons or ${{\mathit \ell}}{{\overline{\mathit \ell}}}$ pairs
▸  Leptonic modes with ${{\mathit \ell}}{{\overline{\mathit \ell}}}$ pairs
▸  Lepton family number ($\mathit LF$), Lepton number ($\mathit L$), $\Delta \mathit S$ = $\Delta \mathit Q$ ($\mathit SQ$) violating modes, or $\Delta \mathit S$ = 1 weak neutral current ($\mathit S1$) modes
[1] See the note in these Particle Listings.
[2] Neglecting photon channels. See, $\mathit e.g.$, A. Pais and S.B. Treiman, Phys. Rev. $\mathbf {D12}$, 2744 (1975).
[3] See the Particle Listings below for the energy limits used in this measurement.
[4] Most of this radiative mode, the low-momentum ${{\mathit \gamma}}$ part, is also included in the parent mode listed without ${{\mathit \gamma}}$'s.
[5] Structure-dependent part.
[6] See the review on ``Form Factors for Radiative Pion and Kaon Decays'' for definitions and details.
[7] Direct-emission branching fraction.
[8] Derived from an analysis of neutrino-oscillation experiments.
[9] The value is for the sum of the charge states or particle/antiparticle states indicated.
[10] Violates angular-momentum conservation.
Constrained Fit information