STRANGE MESONS
($\boldsymbol S$ = $\pm1$, $\boldsymbol C$ = $\boldsymbol B$ = 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 search

${{\boldsymbol K}^{0}}$ $I(J^P)$ = $1/2(0^{-})$

See related review:
$\mathit CPT$ Invariance Tests in Neutral Kaon Decay
${{\mathit K}^{0}}$ MASS   $497.611 \pm0.013$ MeV (S = 1.2)
${\mathit m}_{{{\mathit K}^{0}}}–{\mathit m}_{{{\mathit K}^{\pm}}}$   $3.934 \pm0.020$ MeV (S = 1.6)
${{\mathit K}^{0}}$ MEAN SQUARE CHARGE RADIUS   $-0.077 \pm0.010$ fm${}^{2}$ 
$\boldsymbol T$-VIOLATION PARAMETER IN ${{\boldsymbol K}^{0}}-{{\overline{\boldsymbol K}}^{0}}$ MIXING
ASYMMETRY $\mathit A_{\mathit T}$ IN ${{\mathit K}^{0}}-{{\overline{\mathit K}}^{0}}$ MIXING   $0.0066 \pm0.0016$  
$\boldsymbol CP$-VIOLATION PARAMETERS
Re($\epsilon $)   $0.001596 \pm0.000013$  
$\boldsymbol CPT$-VIOLATION PARAMETERS
REAL PART OF $\delta $   $(2.5 \pm2.3) \times 10^{-4}$  
IMAGINARY PART OF $\delta $   $(-1.5 \pm1.6) \times 10^{-5}$  
Re(y)   $0.0004 \pm0.0025$  
Re(x$_{-}$)   $-0.0029 \pm0.0020$  
$\vert{}{\mathit m}_{{{\mathit K}^{0}}}–{\mathit m}_{{{\overline{\mathit K}}^{0}}}\vert{}/{\mathit m}_{\mathrm {average}}$   $<6 \times 10^{-19}$   CL=90.0%
(${\Gamma}_{{\mathit K}^{0}}−{\Gamma}_{{\overline{\mathit K}}^{0}})/{\mathit m}_{{\mathrm {average}}}$   $(8 \pm8) \times 10^{-18}$  
TESTS OF $\Delta \boldsymbol S$ = $\Delta \boldsymbol Q$ RULE
Re(x$_{+}$)   $-0.0009 \pm0.0030$