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 search

${{\boldsymbol K}_L^0}$

$I(J^P)$ = $1/2(0^{-})$ 
See related reviews:
$\mathit V_{{\mathit {\mathit u}}{\mathit {\mathit d}}}$, $\mathit V_{{\mathit {\mathit u}}{\mathit {\mathit s}}}$ the Cabibbo Angle, and CKM Unitarity
$\mathit CP$ Violation in ${{\mathit K}_L^0}$ Decays
$\Delta \mathit S$ = $\Delta \mathit Q$ in ${{\mathit K}^{0}}$ Decays
${\mathit m}_{{{\mathit K}_L^0} }–{\mathit m}_{{{\mathit K}_S^0} }$   $(52.93 \pm0.09) \times 10^{8}$ $\hbar{}$ s${}^{-1}$ (S = 1.3)
 
${{\mathit K}_L^0}$ MEAN LIFE   $(5.116 \pm0.021) \times 10^{-8}$ s (S = 1.1)
 
$\boldsymbol T$ VIOLATION TESTS IN ${{\boldsymbol K}_L^0}$ DECAYS
Im($\xi $) in ${{\mathit K}_{{\mu3}}^{0}}$ DECAY (from transverse ${{\mathit \mu}}$ pol.)   $-0.007 \pm0.026$  
 
FOOTNOTES
Constrained Fit information