A maximum-likelihood procedure for determining mean lifetimes of V-particles from cloud chamber data is discussed and 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) x 10-10 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 ΤL = (2.9 ± 0.8) x 10-10 sec is found for those cases with 0 < Q ≤ 50 Mev and a value of ΤH = (1.6 ± 0.5) x 10-10 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.
A qualitative discussion of lifetimes is given for the case of 23 charged V-particle decays. For the charged V-particles these data suggest either a lifetime less than that of the neutral V-particles, provided the sample is homogeneous, or a more likely an apparent average lifetime less than that of the neutral V-particles, if the sample is a mixture of two or more types of particles. The possibility of kappa mesons making up a part of these decays is considered and data indicating lifetimes approximately equal to or longer than 10-9 sec for both the kappa and tau mesons are briefly discussed.
