[Rivet] Problem with JADE plugin?

[Andy Buckley]

Hi Gavin et al,

We noticed this week that an apparent tuning problem with a JADE jet
rate analysis is probably actually a problem with either the JADE plugin
in Fastjet (or in how we are using it.)

If you look at the attached plots, you'll see huge deviations from data
at small y_cut values. We thought this was something to be tuned, but as
the Durham alg data looks great with the same generator & tune, and
older versions of the same plot made with our old Fastjet JADE patch
show a good fit to the JADE data, I think it's likely that there is a
problem with the Fastjet plugin implementation.

In case we are making an error in how we use the values that we are
plotting, here's where they come from:

if (jadejet.clusterSeq()) {
  double y_23 = jadejet.clusterSeq()->exclusive_ymerge(2);
  double y_34 = jadejet.clusterSeq()->exclusive_ymerge(3);
  double y_45 = jadejet.clusterSeq()->exclusive_ymerge(4);
  double y_56 = jadejet.clusterSeq()->exclusive_ymerge(5);

(The jadejet object is a Rivet class, but its clusterSeq() method is
directly returning the fastjet::ClusterSequence*.) Does this look okay
to you?

Cheers,
Andy

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