[Rivet] Pileup in Rivet

[Andy Buckley]

On 04/10/10 19:34, Christian Roehr wrote:
> Hallo Andy,
> 
> I am wondering if a certain feature is present in Rivet and if not, how
> to deal with it.
> 
> Currently I'm studying pileup effects, i.e. the presence of particles
> from additional minimum bias scatters within one bunch crossing (some 20
> or so). Effectively, this should be quite easy, since the additional
> scatterings are not colour-connected whatsoever to the tagged event.
> 
> So, the straightforward way of analyzing that should be to simply add
> the fs particles of these minbias events to the final state of the
> original event. And analyze the resulting final state afterwards.
> 
> Is there a possibility to do that in Rivet? I could not find anything
> like that (looked in the documentation and in the 1.2.1 code).
> 
> Any help is very welcome, Andy. :)

Hi Christian,

Sorry, pile-up isn't something that Rivet simulates intrinsically and
isn't planned either. However, it should not be *too* hard to write a
little HepMC filter which aggregates min bias events and superimposes a
number of them on top of a signal event -- with semi-proper beam spot
and N_pileup sampling. We could help with putting that together if you
are interested.

You should also make sure that the same-event pile-up is sufficient: I'm
involved in the detector simulation for ATLAS, and there is actually
quite a bit of complexity to handling the effect of bunch structure on
pile-up, as well as the more homogeneous backgrounds from thermalised
neutrons in the cavern (which will still be bouncing around 10 turns
after a min bias event) and beam halo. We actually do the
superimposition of these at the post-Geant4 stage, so I'm not actually
sure how good HepMC is at dealing with event structures like this...
shouldn't be a problem, I think, but I've said that before ;)

Sorry to disappoint, but as I said if you'd be interested in trying to
make a pile-up builder at HepMC level then I'm sure we'll help with
building it and I would see no reason not to bundle it with Rivet to
help the next person to turn up with the same question!

Cheers,
Andy

-- 
Dr Andy Buckley
SUPA Advanced Research Fellow
Particle Physics Experiment Group, University of Edinburgh