Rivet analyses

title: D0_1996_I399364

Topological distributions of inclusive three- and four-jet events

Experiment: D0 (Tevatron Run 1)

Inspire ID: 399364

Status: VALIDATED

Authors: - Frank Siegert

References: - Phys.Rev.D53:6000-6016,1996 - DOI: 10.1103/PhysRevD.53.6000 - arXiv: hep-ex/9509005

Beams: p- p+

Beam energies: (900.0, 900.0)GeV

Run details: - $p \bar{p} \to$ jets at 1800 GeV with minimum jet pT in analysis = 20 GeV

The global topologies of inclusive three- and four-jet events produced in pbar p interactions are described. The three- and four-jet events are selected from data recorded by the D0 detector at the Fermilab Tevatron Collider operating at a center-of-mass energy of $\sqrt{s}$=1800 GeV. The studies also show that the topological distributions of the different subprocesses involving different numbers of quarks are very similar and reproduce the measured distributions well. The parton-shower Monte Carlo generators provide a less satisfactory description of the topologies of the three- and four-jet events.

Source code:D0_1996_I399364.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Math/LorentzTrans.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// D0 topological distributions of 3- and 4-jet events. class D0_1996_I399364 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(D0_1996_I399364);


/// @name Analysis methods
/// @{

/// Book histograms
void init() {
  const FinalState fs;

  /// @todo Use correct jet algorithm --- tried FJ3 D0RunICone but does
  // not look as good as the Run2 cone alg used here
  declare(FastJets(fs, JetAlg::D0ILCONE, 0.7), "ConeJets");

  book(_h_3j_x3, 1, 1, 1);
  book(_h_3j_x5, 2, 1, 1);
  book(_h_3j_costheta3, 3, 1, 1);
  book(_h_3j_psi, 4, 1, 1);
  book(_h_3j_mu34, 5, 1, 1);
  book(_h_3j_mu35, 6, 1, 1);
  book(_h_3j_mu45, 7, 1, 1);

  book(_h_4j_x3, 8, 1, 1);
  book(_h_4j_x4, 9, 1, 1);
  book(_h_4j_x5, 10, 1, 1);
  book(_h_4j_x6, 11, 1, 1);
  book(_h_4j_costheta3, 12, 1, 1);
  book(_h_4j_costheta4, 13, 1, 1);
  book(_h_4j_costheta5, 14, 1, 1);
  book(_h_4j_costheta6, 15, 1, 1);
  book(_h_4j_cosomega34, 16, 1, 1);
  book(_h_4j_cosomega35, 17, 1, 1);
  book(_h_4j_cosomega36, 18, 1, 1);
  book(_h_4j_cosomega45, 19, 1, 1);
  book(_h_4j_cosomega46, 20, 1, 1);
  book(_h_4j_cosomega56, 21, 1, 1);
  book(_h_4j_mu34, 22, 1, 1);
  book(_h_4j_mu35, 23, 1, 1);
  book(_h_4j_mu36, 24, 1, 1);
  book(_h_4j_mu45, 25, 1, 1);
  book(_h_4j_mu46, 26, 1, 1);
  book(_h_4j_mu56, 27, 1, 1);
  book(_h_4j_theta_BZ, 28, 1, 1);
  book(_h_4j_costheta_NR, 29, 1, 1);
}


void analyze(const Event& event) {
  Jets jets_in = apply<FastJets>(event, "ConeJets")
                     .jets(Cuts::Et > 20 * GeV && Cuts::abseta < 3, cmpMomByEt);

  Jets jets_isolated;
  for (size_t i = 0; i < jets_in.size(); ++i) {
    bool isolated = true;
    for (size_t j = 0; j < jets_in.size(); ++j) {
      if (i != j && deltaR(jets_in[i], jets_in[j]) < 1.4) {
        isolated = false;
        break;
      }
    }
    if (isolated) jets_isolated.push_back(jets_in[i]);
  }

  if (jets_isolated.empty() || jets_isolated[0].Et() < 60.0 * GeV) vetoEvent;

  if (jets_isolated.size() > 2) _threeJetAnalysis(jets_isolated);
  if (jets_isolated.size() > 3) _fourJetAnalysis(jets_isolated);
}


void finalize() {
  normalize(_h_3j_x3);
  normalize(_h_3j_x5);
  normalize(_h_3j_costheta3);
  normalize(_h_3j_psi);
  normalize(_h_3j_mu34);
  normalize(_h_3j_mu35);
  normalize(_h_3j_mu45);
  normalize(_h_4j_x3);
  normalize(_h_4j_x4);
  normalize(_h_4j_x5);
  normalize(_h_4j_x6);
  normalize(_h_4j_costheta3);
  normalize(_h_4j_costheta4);
  normalize(_h_4j_costheta5);
  normalize(_h_4j_costheta6);
  normalize(_h_4j_cosomega34);
  normalize(_h_4j_cosomega35);
  normalize(_h_4j_cosomega36);
  normalize(_h_4j_cosomega45);
  normalize(_h_4j_cosomega46);
  normalize(_h_4j_cosomega56);
  normalize(_h_4j_mu34);
  normalize(_h_4j_mu35);
  normalize(_h_4j_mu36);
  normalize(_h_4j_mu45);
  normalize(_h_4j_mu46);
  normalize(_h_4j_mu56);
  normalize(_h_4j_theta_BZ);
  normalize(_h_4j_costheta_NR);
}

/// @}

private:

/// @name Helper functions
/// @{

void _threeJetAnalysis(const Jets& jets) {
  // >=3 jet events
  FourMomentum jjj(jets[0].mom() + jets[1].mom() + jets[2].mom());
  const double sqrts = _safeMass(jjj);
  if (sqrts < 200 * GeV) return;

  const LorentzTransform cms_boost = LorentzTransform::mkFrameTransformFromBeta(jjj.betaVec());
  vector<FourMomentum> jets_boosted;
  for (Jet jet : jets) {
    jets_boosted.push_back(cms_boost.transform(jet.mom()));
  }
  isortBy(jets_boosted, cmpMomByE);
  FourMomentum p3(jets_boosted[0]);
  FourMomentum p4(jets_boosted[1]);
  FourMomentum p5(jets_boosted[2]);

  Vector3 beam1(0.0, 0.0, 1.0);
  Vector3 p1xp3 = beam1.cross(p3.p3());
  Vector3 p4xp5 = p4.p3().cross(p5.p3());
  const double cospsi = p1xp3.dot(p4xp5) / p1xp3.mod() / p4xp5.mod();

  _h_3j_x3->fill(2.0 * p3.E() / sqrts);
  _h_3j_x5->fill(2.0 * p5.E() / sqrts);
  _h_3j_costheta3->fill(fabs(cos(p3.theta())));
  _h_3j_psi->fill(acos(cospsi) / degree);
  _h_3j_mu34->fill(_safeMass(FourMomentum(p3 + p4)) / sqrts);
  _h_3j_mu35->fill(_safeMass(FourMomentum(p3 + p5)) / sqrts);
  _h_3j_mu45->fill(_safeMass(FourMomentum(p4 + p5)) / sqrts);
}


void _fourJetAnalysis(const Jets& jets) {
  // >=4 jet events
  FourMomentum jjjj(jets[0].momentum() + jets[1].momentum() + jets[2].momentum() + jets[3].momentum());
  const double sqrts = _safeMass(jjjj);
  if (sqrts < 200 * GeV) return;

  const LorentzTransform cms_boost = LorentzTransform::mkFrameTransformFromBeta(jjjj.betaVec());
  vector<FourMomentum> jets_boosted;
  for (Jet jet : jets) {
    jets_boosted.push_back(cms_boost.transform(jet.momentum()));
  }
  isortBy(jets_boosted, cmpMomByE);
  FourMomentum p3(jets_boosted[0]);
  FourMomentum p4(jets_boosted[1]);
  FourMomentum p5(jets_boosted[2]);
  FourMomentum p6(jets_boosted[3]);

  Vector3 p3xp4 = p3.p3().cross(p4.p3());
  Vector3 p5xp6 = p5.p3().cross(p6.p3());
  const double costheta_BZ = p3xp4.dot(p5xp6) / p3xp4.mod() / p5xp6.mod();
  const double costheta_NR = (p3.p3() - p4.p3()).dot(p5.p3() - p6.p3()) / (p3.p3() - p4.p3()).mod()
      / (p5.p3() - p6.p3()).mod();

  _h_4j_x3->fill(2.0 * p3.E() / sqrts);
  _h_4j_x4->fill(2.0 * p4.E() / sqrts);
  _h_4j_x5->fill(2.0 * p5.E() / sqrts);
  _h_4j_x6->fill(2.0 * p6.E() / sqrts);
  _h_4j_costheta3->fill(fabs(cos(p3.theta())));
  _h_4j_costheta4->fill(fabs(cos(p4.theta())));
  _h_4j_costheta5->fill(fabs(cos(p5.theta())));
  _h_4j_costheta6->fill(fabs(cos(p6.theta())));
  _h_4j_cosomega34->fill(cos(p3.angle(p4)));
  _h_4j_cosomega35->fill(cos(p3.angle(p5)));
  _h_4j_cosomega36->fill(cos(p3.angle(p6)));
  _h_4j_cosomega45->fill(cos(p4.angle(p5)));
  _h_4j_cosomega46->fill(cos(p4.angle(p6)));
  _h_4j_cosomega56->fill(cos(p5.angle(p6)));
  _h_4j_mu34->fill(_safeMass(FourMomentum(p3 + p4)) / sqrts);
  _h_4j_mu35->fill(_safeMass(FourMomentum(p3 + p5)) / sqrts);
  _h_4j_mu36->fill(_safeMass(FourMomentum(p3 + p6)) / sqrts);
  _h_4j_mu45->fill(_safeMass(FourMomentum(p4 + p5)) / sqrts);
  _h_4j_mu46->fill(_safeMass(FourMomentum(p4 + p6)) / sqrts);
  _h_4j_mu56->fill(_safeMass(FourMomentum(p5 + p6)) / sqrts);
  _h_4j_theta_BZ->fill(acos(fabs(costheta_BZ)) / degree);
  _h_4j_costheta_NR->fill(fabs(costheta_NR));
}

double _safeMass(const FourMomentum& p) {
  double mass2 = p.mass2();
  if (mass2 > 0.0)
    return sqrt(mass2);
  else if (mass2 < -1.0e-5) {
    MSG_WARNING("m2 = " << mass2 / GeV << " GeV. Assuming m2 = 0.");
    return 0.0;
  }
  else
    return 0.0;
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_3j_x3;
Histo1DPtr _h_3j_x5;
Histo1DPtr _h_3j_costheta3;
Histo1DPtr _h_3j_psi;
Histo1DPtr _h_3j_mu34;
Histo1DPtr _h_3j_mu35;
Histo1DPtr _h_3j_mu45;

Histo1DPtr _h_4j_x3;
Histo1DPtr _h_4j_x4;
Histo1DPtr _h_4j_x5;
Histo1DPtr _h_4j_x6;
Histo1DPtr _h_4j_costheta3;
Histo1DPtr _h_4j_costheta4;
Histo1DPtr _h_4j_costheta5;
Histo1DPtr _h_4j_costheta6;
Histo1DPtr _h_4j_cosomega34;
Histo1DPtr _h_4j_cosomega35;
Histo1DPtr _h_4j_cosomega36;
Histo1DPtr _h_4j_cosomega45;
Histo1DPtr _h_4j_cosomega46;
Histo1DPtr _h_4j_cosomega56;
Histo1DPtr _h_4j_mu34;
Histo1DPtr _h_4j_mu35;
Histo1DPtr _h_4j_mu36;
Histo1DPtr _h_4j_mu45;
Histo1DPtr _h_4j_mu46;
Histo1DPtr _h_4j_mu56;
Histo1DPtr _h_4j_theta_BZ;
Histo1DPtr _h_4j_costheta_NR;
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(D0_1996_I399364, D0_1996_S3214044);

} ```

Aliases: - D0_1996_S3214044