Mean Lifetimes ofV-Particles and Heavy Mesons

A maximum-likelihood procedure for determining mean lifetimes of $V$-particles from cloud-chamber data is applied to samples taken from a group of 134 neutral $V$-particle decays. For 74 events which were consistent with a decay into a proton and a negative $\pi$-meson, a lifetime of (2.5±0.7)×${10}^{-10\mathrm{}}$ sec is obtained. Dividing the data into "low $Q$" and "high $Q$" groups on the basis of the calculated energy release in the decay, a value of ${\tau }_L=(2.9\mathrm{}\pm 0.8)\times {10}^{-10\mathrm{}}$ sec is found for those cases with $0<~Q<~50$ Mev and a value of ${\tau }_H=(1.6\mathrm{}\pm 0.5)\times {10}^{-10\mathrm{}}$ sec is found for those cases with $50<Q<~150$ Mev. While no significant difference exists between these two values, the difference is greater than for other plausible division schemes which are considered.