Measurement Of The Lifetime Of Ks0 Mesons In The Momentum Range 100 To 350 Gev/C

In an experiment at Fermilab we have measured the lifetime of ${K}_{S}^{0}$ mesons produced by 800-GeV/c protons on tungsten. ${K}_{S}^{0}$\ensuremath{\rightarrow}${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ decays from 100 to 350 GeV/c, between 9.3 and 25.3 m from production, were selected for the measurement. The result was (0.8920\ifmmode\pm\else\textpm\fi{}0.0044)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$ sec, in excellent agreement with measurements performed for 2--5-GeV/c ${K}_{S}^{0}$. The lifetime was also calculated for seven momentum bins. The results were completely consistent with Lorentz invariance. No evidence was found for the mometnum dependence suggested by the intermediate-range ``fifth-force'' hypothesis.