[Rivet] FastJets problems

[Hendrik Hoeth]

Thus spake Andy Buckley (andy.buckley at ed.ac.uk):

> > What's the recommended way of accessing Fastjet plugins directly? Or
> > shall I introduce the split-merge parameter as an argument to FastJets(...)?
> 
> The latter, please!

Okay. In SISCONE we currently use 0.5 hard-coded. In CDFJETCLU and
CDFMIDPOINT we use 0.75, also hard-coded.

It turns out that my memory betrayed me and we don't have any other
SISCONE analyses than this STAR analysis in Rivet at all. The reason for
our strange choice of 0.5 as default seems to be this footnote in the
Fastjet manual:

   "Though its default value is 0.5 (retained for backwards
    compatibility of the interface) we strongly recommend using a
    higher value, e.g. 0.75, especially in high-noise environments,
    in order to disfavour the production of monster jets through
    repeated merge operations."

So I will change our default to 0.75, following the recommendations of
the Fastjet authors and the needs of the STAR analysis, and anybody
implementing a SISCONE analysis in the future will as a matter of fact
check this value in our FastJets projection (won't he?) and can then act
accordingly.

Cheers,

     Hendrik  (in KISS mode)

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