The VariableR package is based on the physics described in:
Jets with Variable R.
David Krohn, Jesse Thaler, and Lian-Tao Wang.
JHEP 0906:059 (2009), arXiv:0903.0392.
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Since version 1.2, one uses the following constructor for creating a
VariableRPlugin (see the VariableRplugin.hh header file for more
details, thanks to Nikola Whallon for feedback and a prototype version
with faster clustering times)
VariableRPlugin(double rho, double min_r, double max_r,
ClustType clust_type,
bool precluster=false,
Strategy strategy=VARIABLE_R_DEFAULT_STRATEGY);
with
rho : mass parameter of VR algorithm, where the effective radius is R~rho/pT.
min_r: minimum allowed jet radius
max_r: maximum allowed jet radius
clust_type: AKTLIKE, CALIKE, KTLIKE, for determining the cluster ordering.
For generalized-kt-like behavior, you can enter an arbitrary double
which is matched to the p value of generalized kt.
Recommended usage is AKTLIKE = -1.0
precluster: true to build small kT jets of size min_r before applying VR
strategy : specify the internal clustering strategy. NNFJN2Tiled, the default
for FastJet>=3.2.0 is expected to be faster. Other options are
NNFJN2Plain, NNH, and Native. For FastJet<3.2.0, or when
pre-clustering is requested, the Native strategy is used by default.
The VariableRPlugin can be used via the standard FastJet plugin mechanism.
Note that pre-clustering is deprecated: one should rather use the
FastJet NestedDefs plugin along the following lines:
#include
#include
std::list jet_defs;
jet_defs.push_back(JetDefinition(kt_algorithm, min_r));
contrib::VariableRPlugin vr_plugin(rho,min_r,max_r,clust_type);
jet_defs.push_back(JetDefinition(&vr_plugin));
NestedDefsPlugin nd_plugin(jet_defs);
JetDefinition jet_def(&nd_plugin);
For backwards compatibility with Version 1.0, we define the AKTVR and CAVR
classes with fewer options (plus a KTVR for consistency). These are available
in the VariableR.hh header.
AKTVR(double rho, double max_r): variable-R anti-kT algorithm
CAVR(double rho, double max_r): variable-R Cambridge-Aachen algorithm
KTVR(double rho, double max_r): variable-R kT algorithm
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Note:
- Version 1.2 is based on the NNFJN2Tiled and NNFJN2Plain pairwise
clustering classes available in FastJet>=3.2.0. For earlier versions
of FastJet (or when pre-clustering is requested), one reverts back to
David Krohn's implementation ("Native" strategy)
- Version 1.1 is based on a new clustering code written by David
Krohn, which should be faster than the previous version.
- Version 1.0 had a CoreJetAlgorithm, which allowed the definition of
generic pairwise recombination scheme. This functionality is now
available in the FastJet NNH class, so CoreJetAlgorithm is no longer
needed.