[Rivet] Gentle reminders...

[Frank Siegert]

Frank Siegert, Friday 08 May 2009:
> Short update: After doing this yesterday I noticed that the change from
> D0ILCone -> FastJets(FastJets::D0ILCONE) gives me a different jet
> multiplicity for the same event in D0_2008_S6879055. I am preparing a
> more detailed description and test case in a bug report after the
> lectures.

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).

Frank