We report the results of a precise measurement of the Ds meson lifetime based
on 1662 +/- 56 fully reconstructed Ds -> phi pi decays, from the charm
hadroproduction experiment E791 at Fermilab. Using an unbinned maximum
likelihood fit, we measure the Ds lifetime to be 0.518 +/- 0.014 +/- 0.007 ps.
The ratio of the measured Ds lifetime to the world average D0 lifetime is 1.25
+/- 0.04. This result differs from unity by six standard deviations, indicating
significantly different lifetimes for the Ds and the D0.Comment: 12 pages, 3 figures, 2 table. LaTe