[Rivet] Gentle reminders...

[Frank Siegert]

Frank Siegert, Friday 08 May 2009:
> FastJet's D0ILCone does not seem to respect the pTmin that I pass to
> the constructor, so using:
>
>   FastJets jets(fs, FastJets::D0ILCONE, 0.5, 20.0*GeV);
>   const JetAlg& jetpro = applyProjection<JetAlg>(event, "Jets");
>   const Jets jets = jetpro.jetsByPt();
>
> also produces jets 10 GeV < pT < 20 GeV, because D0ILCone seems to have
> a default Et_min_ratio of 0.5 somewhere in the fastjet source code,
> which the jet_min_Et gets multiplied with.
> Is this to be expected? If so, we should definitely be aware of it in
> all D0ILCone analyses (and maybe others?). Workaround for me at the
> moment, is to specify an explicit pTmin to jetpro.jetsByPt(ptMin).

With this workaround the z+jets analyses seem to work alright. I am 
attaching comparison plots vs. revision 1406, to demonstrate how much of 
an effect the switch to ZFinder and FastJet 2.4 has had.
The only unexpected discrepancy is in the kT jet rates in MC_TVT1960_ZJETS 
(pages 34-42). I would understand a scale factor, because vetoEvent() is 
used together with sumOfWeights(), but the histograms are not simply 
scaled.
Maybe it's related to the problems with jet rates in e+e-, or it has to do 
with the logarithmic axes. It's not a blocker, but would be nice to 
understand nonetheless.

Frank

PS: Ignore that some of the axis labels are broken, I've fixed this on 
trunk later.

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