Implementation of the spherical version of the SISCone algorithm (plugin for fastjet v2.1 upwards) More...
#include <fastjet/SISConeSphericalPlugin.hh>
Public Types | |
| enum | SplitMergeScale { SM_E , SM_Etilde } |
| enum for the different split-merge scale choices; Note that order must be the same as in siscone More... | |
Public Member Functions | |
| SISConeSphericalPlugin (double cone_radius_in, double overlap_threshold_in, int n_pass_max_in=0, double protojet_Emin_in=0.0, bool caching_in=false, SplitMergeScale split_merge_scale_in=SM_Etilde, double split_merge_stopping_scale_in=0.0) | |
| Main constructor for the SISConeSpherical Plugin class. More... | |
| double | protojet_Emin () const |
| minimum energy for a protojet to be considered in the split-merge step of the algorithm More... | |
| double | protojet_or_ghost_Emin () const |
| return the scale to be passed to SISCone as the protojet_Emin – if we have a ghost separation scale that is above the protojet_ptmin, then the ghost_separation_scale becomes the relevant one to use here More... | |
| SplitMergeScale | split_merge_scale () const |
| indicates scale used in split-merge More... | |
| void | set_split_merge_scale (SplitMergeScale sms) |
| sets scale used in split-merge More... | |
| bool | split_merge_use_E_weighted_splitting () const |
| indicate if the splittings are done using the anti-kt distance More... | |
| void | set_split_merge_use_E_weighted_splitting (bool val) |
| virtual bool | supports_ghosted_passive_areas () const |
| overload the default as we don't provide support for passive areas. More... | |
| virtual std::string | description () const |
| plugin description More... | |
| virtual void | run_clustering (ClusterSequence &) const |
| really do the clustering work More... | |
| virtual bool | is_spherical () const |
| returns true because this plugin is intended for spherical geometries (i.e. More... | |
 Public Member Functions inherited from fastjet::SISConeBasePlugin | |
| SISConeBasePlugin () | |
| default ctor More... | |
| SISConeBasePlugin (const SISConeBasePlugin &plugin) | |
| copy constructor More... | |
| void | set_progressive_removal (bool progressive_removal_in=true) |
| set whether to use SISCone with progressive removal instead of the default split_merge step. More... | |
| bool | progressive_removal () const |
| returns true if progressive_removal is enabled More... | |
| double | cone_radius () const |
| the cone radius More... | |
| double | overlap_threshold () const |
| Fraction of overlap energy in a jet above which jets are merged and below which jets are split. More... | |
| int | n_pass_max () const |
| the maximum number of passes of stable-cone searching (<=0 is same as infinity). More... | |
| void | set_split_merge_stopping_scale (double scale) |
| set the "split_merge_stopping_scale": if the scale variable for all protojets is below this, then stop the split-merge procedure and keep only those jets found so far. More... | |
| double | split_merge_stopping_scale () |
| return the value of the split_merge_stopping_scale (see set_split_merge_stopping_scale(...) for description) More... | |
| void | set_use_jet_def_recombiner (bool choice) |
| allow the user to decide if one uses the jet_def's own recombination scheme More... | |
| bool | use_jet_def_recombiner () const |
| indicate if the jet_def's recombination scheme is being used More... | |
| bool | caching () const |
| indicates whether caching is turned on or not. More... | |
| virtual double | R () const |
| the plugin mechanism's standard way of accessing the jet radius More... | |
| virtual bool | supports_ghosted_passive_areas () const |
| return true since there is specific support for the measurement of passive areas, in the sense that areas determined from all particles below the ghost separation scale will be a passive area. More... | |
| virtual void | set_ghost_separation_scale (double scale) const |
| set the ghost separation scale for passive area determinations just in the next run (strictly speaking that makes the routine a non const, so related internal info must be stored as a mutable) More... | |
| virtual double | ghost_separation_scale () const |
| void | set_user_scale (const UserScaleBase *user_scale_in) |
| set a user-defined scale for stable-cone ordering in progressive removal More... | |
| const UserScaleBase * | user_scale () const |
| returns the user-defined scale in use (0 if none) More... | |
| virtual std::string | description () const =0 |
| plugin description More... | |
| virtual void | run_clustering (ClusterSequence &) const =0 |
| really do the clustering work More... | |
| Public Member Functions inherited from fastjet::JetDefinition::Plugin | |
| virtual std::string | description () const =0 |
| return a textual description of the jet-definition implemented in this plugin More... | |
| virtual void | run_clustering (ClusterSequence &) const =0 |
| given a ClusterSequence that has been filled up with initial particles, the following function should fill up the rest of the ClusterSequence, using the following member functions of ClusterSequence: More... | |
| virtual double | R () const =0 |
| virtual bool | supports_ghosted_passive_areas () const |
| return true if there is specific support for the measurement of passive areas, in the sense that areas determined from all particles below the ghost separation scale will be a passive area. More... | |
| virtual void | set_ghost_separation_scale (double scale) const |
| set the ghost separation scale for passive area determinations in future runs (strictly speaking that makes the routine a non const, so related internal info must be stored as a mutable) More... | |
| virtual double | ghost_separation_scale () const |
| virtual bool | exclusive_sequence_meaningful () const |
| if this returns false then a warning will be given whenever the user requests "exclusive" jets from the cluster sequence More... | |
| virtual bool | is_spherical () const |
| returns true if the plugin implements an algorithm intended for use on a spherical geometry (e.g. More... | |
| virtual | ~Plugin () |
| a destructor to be replaced if necessary in derived classes... More... | |
Protected Member Functions | |
| virtual void | reset_stored_plugin () const |
| call the re-clustering itself More... | |
| virtual void | reset_stored_plugin () const =0 |
| call the re-clustering itself More... | |
Additional Inherited Members | |
| Protected Attributes inherited from fastjet::SISConeBasePlugin | |
| double | _cone_radius |
| double | _overlap_threshold |
| int | _n_pass_max |
| bool | _caching |
| double | _split_merge_stopping_scale |
| bool | _use_jet_def_recombiner |
| bool | _progressive_removal |
| double | _ghost_sep_scale |
| const UserScaleBase * | _user_scale |
Detailed Description
Implementation of the spherical version of the SISCone algorithm (plugin for fastjet v2.1 upwards)
SISConeSphericalPlugin is a plugin for fastjet (v2.1 upwards) that provides an interface to the seedless infrared safe cone jet finder by Gregory Soyez and Gavin Salam.
This is the version of SISCone using spherical coordinates. Compared to the original cylindrical version:
- Particles are within a cone if their opening angle relative to the centre of the cone is less than R
- The split-merge step uses the total energy in the protojet as the ordering and overlap-measure variable
The IR safety of the split-merge step is not guaranteed for events consisting of two back-to-back identical heavy particles that decay. This is because of potential degeneracies in the ordering for the split-merge step.
For moderate values of R the problem should not be too severe (or may even be absent for some values of the overlap parameter), however the user should be aware of the issue.
The default split-merge scale may change at a later date to resolve this issue.
SISCone uses geometrical techniques to exhaustively consider all possible distinct cones. It then finds out which ones are stable and sends the result to the Tevatron Run-II type split-merge procedure for overlapping cones.
Four parameters govern the "physics" of the algorithm:
- the cone_radius (this should be self-explanatory!)
- the overlap_threshold is the parameter which dictates how much two jets must overlap (E_overlap/min(E1,E2)) if they are to be merged
- Not all particles are in stable cones in the first round of searching for stable cones; one can therefore optionally have the the jet finder carry out additional passes of searching for stable cones among particles that were in no stable cone in previous passes — the maximum number of passes carried out is n_pass_max. If this is zero then additional passes are carried out until no new stable cones are found.
- Protojet Emin: protojets that are below this Emin (default = 0) are discarded before each iteration of the split-merge loop.
One parameter governs some internal algorithmic shortcuts:
- if "caching" is turned on then the last event clustered by siscone is stored – if the current event is identical and the cone_radius and n_pass_max are identical, then the only part of the clustering that needs to be rerun is the split-merge part, leading to significant speed gains; there is a small (O(N) storage and speed) penalty for caching, so it should be kept off (default) if only a single overlap_threshold is used.
The final jets can be accessed by requestion the inclusive_jets(...) from the ClusterSequence object. Note that these PseudoJets have their user_index() set to the index of the pass in which they were found (first pass = 0). NB: This does not currently work for jets that consist of a single particle.
For further information on the details of the algorithm see the SISCone paper, arXiv:0704.0292 [JHEP 0705:086,2007].
For documentation about the implementation, see the siscone/doc/html/index.html file.
Definition at line 94 of file SISConeSphericalPlugin.hh.
Member Enumeration Documentation
◆ SplitMergeScale
enum for the different split-merge scale choices; Note that order must be the same as in siscone
| Enumerator | |
|---|---|
| SM_E | Energy (IR unsafe with momentum conservation) |
| SM_Etilde | sum_{i \in jet} E_i [1+sin^2(theta_iJ)] |
Definition at line 99 of file SISConeSphericalPlugin.hh.
Constructor & Destructor Documentation
◆ SISConeSphericalPlugin()
|
inline |
Main constructor for the SISConeSpherical Plugin class.
Definition at line 107 of file SISConeSphericalPlugin.hh.
Member Function Documentation
◆ protojet_Emin()
|
inline |
minimum energy for a protojet to be considered in the split-merge step of the algorithm
Definition at line 127 of file SISConeSphericalPlugin.hh.
◆ protojet_or_ghost_Emin()
|
inline |
return the scale to be passed to SISCone as the protojet_Emin – if we have a ghost separation scale that is above the protojet_ptmin, then the ghost_separation_scale becomes the relevant one to use here
Definition at line 133 of file SISConeSphericalPlugin.hh.
◆ split_merge_scale()
|
inline |
indicates scale used in split-merge
Definition at line 137 of file SISConeSphericalPlugin.hh.
◆ set_split_merge_scale()
|
inline |
sets scale used in split-merge
Definition at line 139 of file SISConeSphericalPlugin.hh.
◆ split_merge_use_E_weighted_splitting()
|
inline |
indicate if the splittings are done using the anti-kt distance
Definition at line 142 of file SISConeSphericalPlugin.hh.
◆ set_split_merge_use_E_weighted_splitting()
|
inline |
Definition at line 143 of file SISConeSphericalPlugin.hh.
◆ supports_ghosted_passive_areas()
|
inlinevirtual |
overload the default as we don't provide support for passive areas.
Reimplemented from fastjet::SISConeBasePlugin.
Definition at line 148 of file SISConeSphericalPlugin.hh.
◆ description()
|
virtual |
plugin description
Implements fastjet::SISConeBasePlugin.
Definition at line 89 of file SISConeSphericalPlugin.cc.
◆ run_clustering()
|
virtual |
really do the clustering work
Implements fastjet::SISConeBasePlugin.
Definition at line 140 of file SISConeSphericalPlugin.cc.
◆ is_spherical()
|
inlinevirtual |
returns true because this plugin is intended for spherical geometries (i.e.
it's an e+e- algorithm).
Reimplemented from fastjet::JetDefinition::Plugin.
Definition at line 156 of file SISConeSphericalPlugin.hh.
◆ reset_stored_plugin()
|
protectedvirtual |
call the re-clustering itself
Implements fastjet::SISConeBasePlugin.
Definition at line 297 of file SISConeSphericalPlugin.cc.
The documentation for this class was generated from the following files:
- plugins/SISCone/fastjet/SISConeSphericalPlugin.hh
- plugins/SISCone/SISConeSphericalPlugin.cc
