We have measured the lifetime of the ${\overline{\Sigma }}^{-}$ using the Fermilab Proton Center 375 GeV/$c$ charged hyperon beam. We obtained $(80.43\mathrm{}\pm 0.80\pm 0.14)$ ps. We also measured the lifetime of the ${\Sigma }^{+},$ obtaining $(80.38\mathrm{}\pm 0.40\pm 0.14)$ ps, in agreement with the Particle Data Group value. A direct comparison between the two lifetimes from the ratio of the decay curves gives a fractional lifetime difference of $\Delta \tau /\overline{\tau }=(-0.06\pm 1.12)\%,$ consistent with equal lifetimes for baryon and antibaryon as required by CPT invariance.

• Received 4 October 1999

DOI:https://doi.org/10.1103/PhysRevD.61.031101