This page is only relevant for FastJet 2 users

Updated 2011-05-21 with links to a couple of new tools

For the next version of FastJet we plan to include a set of "Tools" to help deal with jets subsequent to finding them.

On this page we're starting to collect some of the ingredients that may go into the tools part of the next release. We're not quite sure what the final interfaces will look like, so anything that's below should be taken as subject to future evolution (and the documentation isn't quite there yet either).

This page also includes links to other people's code that provides related functionality.

To get started with these tools, have a look also at the Boost 2010 tutorial.

If you have requests, or code that you would like to contribute, let us know.

Boosted object finding

  • YSplitter, from hep-ph/0201098 (Butterworth, Cox and Forshaw). You just need to call the ClusterSequence::exclusive_subdmerge(...) method on your jet.

  • Higgs tagging as performed in arXiv:0802.2470 (Butterworth, Davison, Salam and Rubin) is available in any recent distribution of FastJet as example/, which also illustrates the filtering step.

  • The Johns Hopkins Top Tagger (arXiv:0806.0848, Kaplan, Rehermann, Schwartz and Tweedie), JHTopTagger.hh. The method is by the Johns Hopkins group, the code is by the FastJet authors.

  • The Centre of Mass Top Tagger, by Gavin Salam (unpublished), which performs comparably to the Johns Hopkins one, but involves fewer parameters and sculpts the W mass distribution less in background events, CMTopTagger.hh.

  • The Seattle Pruning method of arXiv:0903.5081 (Ellis, Vermillion and Walsh) is available as a FastJet plugin from its authors' web site.

  • A simple generic Cambridge/Aachen subjet finder (as described in arXiv:0906.0728, Butterworth, Ellis, Raklev and Salam), CASubJet.hh, designed to have fewer tunable parameters than the boosted Higgs tagger and to give relatively unsculpted backgrounds (dm/m).

  • The HEPTopTagger, based on 0910.5472 and 1006.2833 is available on request from Tilman Plehn, via this page.

  • The multivariate W-jet tagger from Cui, Han and Schwartz (1012.2077) also has a page of its own.
Some of the code extracts above make use of the Range.hh helper class and all the ones from the FastJet group assume that the ClusterSequence is based on the Cambridge/Aachen algorithm (though they might not always check that assumption...).

Other tools

  • Filtering, introduced in arXiv:0802.2470 for boosted particle reconstruction, and applicable also for limiting UE/pileup in normal jets: breaks a jet (or several jets) into subjets on an angular scale Rfilt and keeps only the nfilt hardest.

    The code, Filter.hh and, by the FastJet authors, is to be used for post-processing jets, and also includes two further options: 1) subtracting noise before choosing which subjets to filter (e.g., as in arXiv:0810.1304); 2) keeping subjets above some pt cut, which is closely related to the "Trimming" proposal by Krohn, Thaler & Wang (next entry) and which they found improves over just tuning nfilt and Rfilt in dijet mass reconstructions.

    The version of 2010-11-05 augments FilteredJet so that it has a constituents() member function (the exact interface will still evolve in the future and is previewed in the 3.0alpha2 release of FastJet).

  • Trimming, arXiv:0912.1342 by Krohn, Thaler & Wang, available as a plugin from their web-site.