I could probably tease this information out of the Particle Data Group website, given enough time, but somebody with a background in particle physics can probably answer this in two seconds, so I appeal to the Internets:
What is the shortest lifetime of a particle that has been directly detected?
By “directly detected” I mean, well, directly detected. Something that has been identified from a track in a detector, or a click in a calorimeter, and not something whose existence has been inferred from a resonance observed in the production of other things.
My half-assed guess would be a neutral pion, with a lifetime on the order of 10-16s, but I could easily be wrong. So what’s the right answer?
(This is a factoid to be dropped in a discussion of “virtual particles” in my book. I could just as easily skip it, but it ocurred to me as something to throw in, so if I can get the answer, I’ll use it…)
(The “neutral pion” guess is because I know that pions were discovered relatively early, and I know that the neutral pion has a really short lifetime. I’m not sure about the detection history, though.)