hephysics.jet

Class SCJet

java.lang.Object

hephysics.jet.SCJet

public class SCJet
extends java.lang.Object

SCJet is an implementation of the longitudinally-invariant kT, anti-KT and Cambridge/Aachen clustering algorithms. The algorithm uses rapidity-phi for the distance parameter and double values for merging. The input and output for this algorithm is ParticleD class.

This class uses double values for calculations, caching and requires more memory, compared to the light-weight KTjet class that uses floats and pseudo-rapidity to define the distance parameter. This implementation can access jet constituents.

This algorithm is similar to the FastJet http://fastjet.fr/ implementation that uses rapidity. Use light-weight KTjet class when using pseudo-rapidity and phi to define distance parameters. The method uses E-scheme to combine particles (p1+p2). More details is in http://arxiv.org/pdf/hep-ph/0210022v1.pdf.

Constructor Summary

Constructors

Constructor and Description
SCJet(double R, double minpt) Initialize calculations of the kT algorithm.
SCJet(double R, int recom, int mode, double minpt) Initialize calculations of the longitudinally invariant kT algorithm in inclusive mode.
SCJet(double R, int recom, int mode, double minpt, boolean isfast) Initialize calculations of the longitudinally invariant kT algorithm in inclusive mode.

Method Summary

Modifier and Type	Method and Description
java.util.List<ParticleD>	buildJets(java.util.List<ParticleD> list) Run the jet algorithm using the list of particles.
double	getDistance(ParticleD a, ParticleD b) Calculate R distance in y-phi.
java.util.ArrayList<ParticleD>	getJetsSorted() Get jets after sorting in jet pT.
double	getKtDistance1(ParticleD a) This is the KT distance to the beam (assuming Z=Y=0).
double	getKtDistance12(ParticleD a, ParticleD b) Calculate delta R distance.
static void	main(java.lang.String[] args) Main class for testing.
void	printJets() Print the kT jets for debugging.
void	setDebug(boolean debug) Print debugging information.
java.lang.String	toString() Print the kT jets for debugging to a string.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SCJet

public SCJet(double R,
             int recom,
             int mode,
             double minpt,
             boolean isfast)

Initialize calculations of the longitudinally invariant kT algorithm in inclusive mode. Jet can be clustered using Cambridge/Aachen or anti-kT approaches, depending on the "mode" parameter. The distance parameters are rapidity and phi.

Parameters:

R - distance measure

recom - recombination scheme.
1: The E-scheme Simple 4-vector addition.
2: The pT-scheme.
3: The pT^2 scheme.
Currently only E-scheme is implemented.

mode - clustering mode dij=min(kT_i^{2* mode},kT_j^{2* mode})).
mode=1 means inclusive kT jet algorithm
mode=0 means Cambridge/Aachen jet algorithm
mode=-1 means anti-KT jet algorithm

minpt - min pT for final jets.

isfast - if true, use a seeded anti-KT algorithm. This algorithm is faster, but some difference may exist with the original anti-KT (i.e. when true is set) for soft jets. If false, use the traditional that scales as N^3 (slow).

SCJet

public SCJet(double R,
             int recom,
             int mode,
             double minpt)

Initialize calculations of the longitudinally invariant kT algorithm in inclusive mode. Jet can be clustered using Cambridge/Aachen or anti-kT approaches, depending on the "mode" parameter. The distance parameters are rapidity and phi. Fast mode is disabled.

Parameters:

R - distance measure

recom - recombination scheme.
1: The E-scheme Simple 4-vector addition.
2: The pT-scheme.
3: The pT^2 scheme.
Currently only E-scheme is implemented.

mode - clustering mode dij=min(kT_i^{2* mode},kT_j^{2* mode})).
mode=1 means inclusive kT jet algorithm
mode=0 means Cambridge/Aachen jet algorithm
mode=-1 means anti-kT jet algorithm

minpt - min pT for final jets.

SCJet

public SCJet(double R,
             double minpt)

Initialize calculations of the kT algorithm. Meaningful values are R=0.2- 1. Jets are clustered in rapidity and phi space. The The E-scheme with 4-vector addition is used.

Parameters:

R - distance measure

minpt - min pT for final jets.

Method Detail

buildJets

public java.util.List<ParticleD> buildJets(java.util.List<ParticleD> list)

Run the jet algorithm using the list of particles.

Parameters:

list - list with particles

Returns:

final jets without sorting.

getJetsSorted

public java.util.ArrayList<ParticleD> getJetsSorted()

Get jets after sorting in jet pT. Run buildJets before calling this method.

Returns:

list with sorted jets

printJets

public void printJets()

Print the kT jets for debugging.

toString

public java.lang.String toString()

Print the kT jets for debugging to a string.

Overrides:

toString in class java.lang.Object

Returns:

String representing a jet

getKtDistance12

public double getKtDistance12(ParticleD a,
                              ParticleD b)

Calculate delta R distance.

Parameters:

a - input particle

b - input particle

p - power parameter

Returns:

Kt distance

getDistance

public double getDistance(ParticleD a,
                          ParticleD b)

Calculate R distance in y-phi.

Parameters:

a - input particle

b - input particle

Returns:

y-phi distance

getKtDistance1

public double getKtDistance1(ParticleD a)

This is the KT distance to the beam (assuming Z=Y=0). The distance measure depends on the mode parameter.

Parameters:

a - particle

Returns:

kT distance

setDebug

public void setDebug(boolean debug)

Print debugging information. It shows how much time spend to make jets in ms.

Parameters:

debug - true if printing benchmark information.

main

public static void main(java.lang.String[] args)

Main class for testing.

Parameters:

args -