[Rivet] normalisation to cross-sections

[Hendrik Hoeth]

Just to clarify things a bit more:

Thus spake Frank Siegert (frank.siegert at durham.ac.uk):

> If I run 10 x 1 million events to get high statistics in short time,
> then I want to be able to combine the resulting 10 histograms into
> one. [...] this doesn't work, because there might be runaway bins
> which create a bias towards low values for all other bins.

This problem only appears in distributions where not all events are
filled into the histogram (i.e. after cuts) in combination with weighted
events.

-- 
"You have to take the most direct road to go instead of your
 meeting, you have to, this one ended, leave at once the CERN
 domain."         (imprint on the CERN visitor ID cards)