[Rivet] Rivet: Accessing intermediate particles

[Hendrik Hoeth]

Hi David,

Thus spake David Hall (David.Hall at physics.ox.ac.uk):

> Unfortunately, when I check the status of each parent of the electron
> in an event, I find that they are _all_ status 2. This suggests that
> all the electrons are from decays, but I know this shouldn't be the
> case. Two should be from the hard scatter. Is it possible this is
> specific to Sherpa?

Well, technically even in the hard scatter the electrons are decay
products of something. Though luck, eh? I mean ...

> >>I understand the philosophy behind Rivet not providing access to the
> >>intermediate particles, but I believe that looking for the particles
> >>from the hard process in this way is not _so_ bad. :-)

... nature doesn't mark the particles from the hard process, either. So
the best thing is to resort to physically meaningful observables,
similar to what you do in the experiment.

Cheers,

    Hendrik

PS: I assume you know you can walk through the whole HepMC tree in the
same way you asked for the electrons' parents. That's all the generator
supplies.

-- 
Man is the best computer we can put aboard a spacecraft, and
the only one that can be mass produced with unskilled labor.
                                        -- Wernher von Braun