https://phys.org/news/2018-05-doubly-charmed-particle.html

The Ξcc++ particle is fleeting: it decays quickly into lighter particles. In fact it was through its decay into a Λc+ baryon and three lighter mesons, K-, π+ and π+, that it was discovered. Since then, LHCb physicists have been carrying on an analysis to determine its lifetime with a high level of precision. The value obtained is 0.256 picoseconds (0.000000000000256 seconds), with a small degree of uncertainty. Though very small in everyday life, such an amount of time is relatively large in the realm of subatomic particles. The measured value is within the range predicted by theoretical physicists on the basis of the Standard Model, namely between 0.20 and 1.05 picoseconds.

To achieve this precise result, LHCb physicists compared the measurement of the lifetime of the Ξcc++ with that of another particle whose lifetime is well-known. They based their measurements on the same sample of events that led to the discovery.