[Rivet] Rivet Jet Analysis

[Andy Buckley]

On 31/01/11 15:26, Hendrik Hoeth wrote:
> Hi Sam,
> 
> Thus spake Andy Buckley (andy.buckley at ed.ac.uk):
> 
>>> For the CDF_2008_LEADINGJETS  <Nch> against pT(leading jet) plots, the
>>> runs from each pT cut are needed to fill a single histogram. Should I
>>> deal with this by chopping each histogram down to its valid region (say
>>> 0-20 pT for the minimum bias run, then 20-100pT for the pTmin=10GeV run
>>> etc) then stick all these together to make a complete distribution? Or
>>> is there a smarter way of doing this.
> 
> Currently we do exactly that. There is a script that can do the
> histogram slicing and merging for you: rivet-mergeruns. It's a bit
> awkward to use, since it's not exactly aimed at end-users, but
> nevertheless. Here is how I used it in a recent Pythia-8 production:
> 
> rivet-mergeruns CDF_2008_LEADINGJETS_CKIN0/Rivet.aida:1960:0 \
>                 CDF_2008_LEADINGJETS_CKIN10/Rivet.aida:1960:30 \
>                 CDF_2008_LEADINGJETS_CKIN20/Rivet.aida:1960:50 \
>                 CDF_2008_LEADINGJETS_CKIN50/Rivet.aida:1960:80 \
>                 CDF_2008_LEADINGJETS_CKIN100/Rivet.aida:1960:130 \
>                 CDF_2008_LEADINGJETS_CKIN150/Rivet.aida:1960:180 \
>                 > foo.dat
> flat2aida foo.dat
> 
> You have to specify <aidafile>:<energy>:<mergingpT>. Note that you need
> to set the histogram merging pT a fair bit higher than the generator
> level cut!

And also note that the analyses that it applies to and how it merges
them is determined not by the command line (which just tells the script
which .aida files should be considered as appropriate at which energy
and above which pT cut) but by hard-coded declarations in the script
itself! That's why Hendrik says that it's not really intended for
end-user use... and why I didn't mention it ;) You can hack the script
for your own purposes if it doesn't already handle all the analyses that
you need... but from what you mentioned in your previous mail, I think
it does.

However, I still strongly think that pT-enhancement/weighting is a
better way. PYTHIA 6 had a limited version of that so *surely* Pythia 8
has something... and hopefully more configurable, too. With the approach
above, you can only merge multiple runs together inside a single
(profile) histogram if that histogram is binned in the pT of a leading
jet -- because that is effectively the quantity that the generator-level
cut is applied on. But the pT-enhancement method will work for general
histograms, and will fill such pT_lead profiles with smooth statistics
rather than the sort of sawtooth that comes from merging together
different single-cut pT slices.

Cheers,
Andy

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

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