Jet Finders
Pythia comes with three built-in
jet finders, ClusterJet for e^+e^- events
and SlowJet and CellJetfor hadron collider ones.
Especially the latter is not so well matched to the standards of its field,
however. (But it is closely related to the anti-kT algorithm,
so is also not completely disconnected [Cac08].)
SlowJet can do jet finding according to the current-day
kT, Cambridge/Aachen and anti-kT algorithms but,
as the name indicates, is is rather slow, especially when compared with
the FastJet alternative.
FastJet
For realistic jet studies the FastJet package
[Cac06] has become a standard. Several different
jet options are available, such as kT,
Cambridge/Aachen, anti-kT and SISCone.
Linking to FastJet is foreseen in the configure
file in the examples subdirectory, and the
main71.cc and main72.cc programs contain
examples how it can be used with Pythia events.
The latter program makes use of the include/FastJet3.h
header file, contributed by Gavin Salam. This allows simple input
of a Pythia particle into a FastJet one,
either retaining only the four-momentum or the full particle information.
Thereby more sophisticated selectors become possible at the
FastJet level.