[Rivet] lifetimes in rivet

[Hendrik Hoeth]

Thus spake Jonathan Butterworth (jmb at hep.ucl.ac.uk):

> The advantage would (might) be e.g. if there were several different 
> analyses with slightly different stability criteria, one could run the 
> them in a single run this way, rather than having separate generator 
> runs for each. But its a bit hypothetical.

I agree this is hypothetical. Rather than checking in Rivet whether or
not the user used the proper MC setup and then crawl through the event
history to find the parent particle in case the user screwed up (talking
about being generator-independent ...), we should encourage the use of
correct generator setups.

Cheers,

    Hendrik

-- 
"Two equal numbers are equivalent, even if they come from two
 different people one of which you don't like"
(MLM about the theoretical top cross-section, in a meeting
about theoretical uncertainties on the top mass)