fastjet::EECambridgePlugin Class Reference

EECambridgePlugin is a plugin for fastjet (v2.4 upwards). More...

#include <EECambridgePlugin.hh>

Inheritance diagram for fastjet::EECambridgePlugin:

[legend]

Collaboration diagram for fastjet::EECambridgePlugin:

[legend]

List of all members.

Public Member Functions
	EECambridgePlugin (double ycut)
	Main constructor for the EECambridge Plugin class.
	EECambridgePlugin (const EECambridgePlugin &plugin)
	copy constructor
virtual std::string	description () const
	return a textual description of the jet-definition implemented in this plugin
virtual void	run_clustering (ClusterSequence &) const
	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: plugin_do_ij_recombination(.
double	ycut () const
virtual double	R () const
	the plugin mechanism's standard way of accessing the jet radius.
virtual bool	exclusive_sequence_meaningful () const
	avoid the warning whenever the user requests "exclusive" jets from the cluster sequence
Private Attributes
double	_ycut

---

Detailed Description

EECambridgePlugin is a plugin for fastjet (v2.4 upwards).

It implements the Cambridge algorithm, as defined in

Better jet clustering algorithms Yuri Dokshitzer, Garth Leder, Stefano Moretti, Bryan Webber JHEP 9708 (1997) 001 http://www-spires.slac.stanford.edu/spires/find/hep/www?rawcmd=FIND+j+JHEPA%2C9708%2C001

On construction one must supply a ycut value.

To get the jets at the end call ClusterSequence::inclusive_jets();

Definition at line 57 of file EECambridgePlugin.hh.

---

Constructor & Destructor Documentation

fastjet::EECambridgePlugin::EECambridgePlugin

(

double

ycut

)

[inline]

Main constructor for the EECambridge Plugin class.

It takes the dimensionless parameter ycut (the Q value for normalisation of the kt-distances is taken from the sum of all particle energies).

Definition at line 62 of file EECambridgePlugin.hh.

: _ycut(ycut) {}

fastjet::EECambridgePlugin::EECambridgePlugin

(

const EECambridgePlugin &

plugin

)

[inline]

copy constructor

Definition at line 65 of file EECambridgePlugin.hh.

                                                       {
    *this = plugin;
  }

---

Member Function Documentation

string fastjet::EECambridgePlugin::description

(

)

const [virtual]

return a textual description of the jet-definition implemented in this plugin

Implements JetDefinition::Plugin.

Definition at line 71 of file EECambridgePlugin.cc.

References ycut().

                                             {
  ostringstream desc;
  desc << "EECambridge plugin with ycut = " << ycut() ;
  return desc.str();
}

virtual bool fastjet::EECambridgePlugin::exclusive_sequence_meaningful

(

)

const [inline, virtual]

avoid the warning whenever the user requests "exclusive" jets from the cluster sequence

Reimplemented from JetDefinition::Plugin.

Definition at line 82 of file EECambridgePlugin.hh.

{return true;}

virtual double fastjet::EECambridgePlugin::R

(

)

const [inline, virtual]

the plugin mechanism's standard way of accessing the jet radius.

This must be set to return something sensible, even if R does not make sense for this algorithm!

Implements JetDefinition::Plugin.

Definition at line 78 of file EECambridgePlugin.hh.

{return 1.0;}

void fastjet::EECambridgePlugin::run_clustering

(

ClusterSequence &

)

const [virtual]

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:

• plugin_do_ij_recombination(.

..)

• plugin_do_iB_recombination(...)

Implements JetDefinition::Plugin.

Definition at line 77 of file EECambridgePlugin.cc.

References ClusterSequence::jets(), fastjet::d0::inline_maths::min(), ClusterSequence::plugin_record_iB_recombination(), ClusterSequence::plugin_record_ij_recombination(), ClusterSequence::Q2(), and ycut().

                                                                 {
  int njets = cs.jets().size();
  NNH<EECamBriefJet> nnh(cs.jets());

  double Q2 = cs.Q2(); 

  while (njets > 0) {
    int i, j, k;
    // here we get a minimum based on the purely angular variable from the NNH class
    // (called dij there, but vij in the Cambridge article (which uses dij for 
    // a kt distance...)
    double vij = nnh.dij_min(i, j); // i,j are return values...

    // next we work out the dij (ee kt distance), and based on its
    // value decide whether we have soft-freezing (represented here by
    // a "Beam" clustering) or not
    double dij;
    if (j >= 0) {
      double scale = min(cs.jets()[i].E(), cs.jets()[j].E());
      dij = 2 * vij * scale * scale;
      if (dij > Q2 * ycut()) {
        // we'll call the softer partner a "beam" jet
        if (cs.jets()[i].E() > cs.jets()[j].E()) swap(i,j);
        j = -1;
      }
    } else {
      // for the last particle left, just use yij = 1
      dij = Q2;
    }
    
    if (j >= 0) {
      cs.plugin_record_ij_recombination(i, j, dij, k);
      nnh.merge_jets(i, j, cs.jets()[k], k);
    } else {
      cs.plugin_record_iB_recombination(i, dij);
      nnh.remove_jet(i);
    }
    njets--;
  }
    
}

double fastjet::EECambridgePlugin::ycut

(

)

const [inline]

Definition at line 73 of file EECambridgePlugin.hh.

Referenced by description(), and run_clustering().

{return _ycut;}

---

Member Data Documentation

double fastjet::EECambridgePlugin::_ycut [private]

Definition at line 85 of file EECambridgePlugin.hh.

---

The documentation for this class was generated from the following files:

• plugins/EECambridge/fastjet/EECambridgePlugin.hh
• plugins/EECambridge/EECambridgePlugin.cc