[Rivet] [Fastjet] Problem with JADE plugin?

[Gavin Salam]

Hi Andy,

This is puzzling. What you're doing looks right.

Do you still have your original Jade plugin to compare with? The best way 
of carrying out diagnostics is event-by-event comparisons of the 
jets/cluster-sequence.

There's also the question of recombination scheme (e.g. use of energies v. 
3-momenta), but I thought we'd implemented what was written in the Jade 
paper.

You can also try exclusive_ymerge_max (but I don't think it'll make much 
difference -- I'm not sure which corresponds to what Jade did).

Cheers,
Gavin


On Wed, 23 Jun 2010, Andy Buckley wrote:

> Date: Wed, 23 Jun 2010 14:46:59
> From: Andy Buckley <andy.buckley at ed.ac.uk>
> Reply-To: "Email the developers \\(subscription not required\\)"
>     <fastjet at projects.hepforge.org>
> To: fastjet at projects.hepforge.org
> Cc: Rivet <rivet at projects.hepforge.org>
> Subject: [Fastjet] Problem with JADE plugin?
> 
> 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
>