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Rivet analyses reference
OPAL_2004_I648738
Quark and gluon jet fragmentation functions
Experiment: OPAL (LEP)
Inspire ID: 648738
Status: VALIDATED
Authors:
References:
- Eur.Phys.J. C37 (2004) no.1, 25-47
- hep-ex/0404026
Beams: e+ e-
Beam energies: (6.4, 6.4); (13.4, 13.4); (24.0, 24.0); (45.6, 45.6); (46.5, 46.5); (48.5, 48.5); (98.5, 98.5) GeV
Run details:
- For quark fragmentation $e^+e^-\to q\bar{q}$ events are required, while for gluon fragmentation the fictional $e^+e^-\to gg$ process is required.
Measurement of the fragmentation functions for quarks and gluons at LEP. Useful for studying the properties of gluon jets and the differences between quark and gluon jets. For the study of gluon jets the fictional $e^+e^-\to g g $ process must be used. The data in histograms labelled "hemisphere fragmentation" are measured from jets defined by hemispheres, with an energy scale defined by $E=\sqrt{s}/2$, while data in histograms named "durham fragmentation" are measured from jets defined by the durham algorithm with $Q_\mathrm{jet}=E_\mathrm{jet}\sin(\theta/2)$ as the energy scale. The rivet analysis defines the jet flavour from the initial quarks, as the data are corrected for impurities, and defines all jets as hemispheres with energy scale $E=\sqrt{s}/2$.
Source code:
OPAL_2004_I648738.cc
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118 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
namespace Rivet {
class OPAL_2004_I648738 : public Analysis {
public:
/// Constructor
OPAL_2004_I648738()
: Analysis("OPAL_2004_I648738"), _sumW(3), _histo_xE(3)
{ }
/// @name Analysis methods
//@{
void init() {
declare(FinalState(), "FS");
declare(ChargedFinalState(), "CFS");
unsigned int ih=0;
if (inRange(0.5*sqrtS()/GeV, 4.0, 9.0)) {
ih = 1;
}
else if (inRange(0.5*sqrtS()/GeV, 9.0, 19.0)) {
ih = 2;
}
else if (inRange(0.5*sqrtS()/GeV, 19.0, 30.0)) {
ih = 3;
}
else if (inRange(0.5*sqrtS()/GeV, 45.5, 45.7)) {
ih = 5;
}
else if (inRange(0.5*sqrtS()/GeV, 30.0, 70.0)) {
ih = 4;
}
else if (inRange(0.5*sqrtS()/GeV, 91.5, 104.5)) {
ih = 6;
}
assert(ih>0);
// book the histograms
book(_histo_xE[0], ih+5,1,1);
book(_histo_xE[1], ih+5,1,2);
if(ih<5) book(_histo_xE[2] ,ih+5,1,3);
book(_sumW[0], "_sumW_0");
book(_sumW[1], "_sumW_1");
book(_sumW[2], "_sumW_2");
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// find the initial quarks/gluons
Particles initial;
for (ConstGenParticlePtr p : HepMCUtils::particles(event.genEvent())) {
ConstGenVertexPtr pv = p->production_vertex();
const PdgId pid = abs(p->pdg_id());
if(!( (pid>=1&&pid<=5) || pid ==21) ) continue;
bool passed = false;
for (ConstGenParticlePtr pp : HepMCUtils::particles(pv, Relatives::PARENTS)) {
const PdgId ppid = abs(pp->pdg_id());
passed = (ppid == PID::ELECTRON || ppid == PID::HIGGS ||
ppid == PID::ZBOSON || ppid == PID::GAMMA);
if(passed) break;
}
if(passed) initial.push_back(Particle(*p));
}
if(initial.size()!=2) {
vetoEvent;
}
// type of event
unsigned int itype=2;
if(initial[0].pid()==-initial[1].pid()) {
PdgId pid = abs(initial[0].pid());
if(pid>=1&&pid<=4)
itype=0;
else
itype=1;
}
assert(itype<_histo_xE.size());
// fill histograms
_sumW[itype]->fill(2.);
const Particles& chps = applyProjection<FinalState>(event, "CFS").particles();
for(const Particle& p : chps) {
double xE = 2.*p.E()/sqrtS();
_histo_xE[itype]->fill(xE);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<_histo_xE.size();++ix) {
if(_sumW[ix]->val()>0.) scale(_histo_xE[ix],1./ *_sumW[ix]);
}
}
//@}
private:
vector<CounterPtr> _sumW;
/// @name Histograms
//@{
vector<Histo1DPtr> _histo_xE;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(OPAL_2004_I648738);
}
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