Measurement of the lifetime ofKS0mesons 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. $K_S^0$→${\pi }^{+}$ ${\pi }^{\mathrm{-}}$ 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±0.0044)×${10}^{\mathrm{-}10}$ 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.