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source: svn/trunk/external/fastjet/plugins/CMSIterativeCone/README

Last change on this file was 859, checked in by Pavel Demin, 12 years ago

update fastjet to version 3.0.3

File size: 1.4 KB
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1Note on the implementation of the CMS Iterative Plugin
2
3The code is initially the CMSSW implementation in
4CMSIterativeConeAlgorithm.cc in /CMSSW/RecoJets/JetAlgorithms
5(more precisely, Revision 14 of the cc file)
6
7To avoid importing too many files from CMSSW, we did a couple of
8modifications starting from the CMSIterativeConeAlgorithm file:
9
10 - directly used the FastJet PseudoJet instead of the InputItem
11 present initially. Note that access to the info then has to be done
12 using . instead of -> which implies a few small modifications here
13 and there.
14
15 - added a small piece of code to compute Et. That peice of code is
16 the same as tracked down in the CMS code. It comes from the Root
17 Lorentzvector, more precisely, the PxPyPzE4D implementation.
18
19 - The ordering in Et, NumericSafeGreaterByEt, is imported from
20 EtComparator.h in PhysicsTools/Utilities/
21
22 - The DeltaR2 computation is imported from DeltaR.cc and DeltaPhi.cc
23 in CMSSW/DataFormats/Math
24
25 - finally, instead of the ProtoJet construction, we use the
26 ClusterSequence-compatible clustering. That one follows the line of
27 what is done in the SISCone plugin. Note that ve've checked in the
28 CMSSZ code that the protojet is indeed reconstructed using E-scheme
29 recombination (while the stability test is done using Et-scheme)
30
31Finally, we want to thank Andreas Oehler for pointing us to the CMS
32code.
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