Rivet analyses

title: BELLE_2009_I811289

$J/\psi$ production at 10.6 GeV

Experiment: BELLE (KEKB)

Inspire ID: 811289

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 79 (2009) 071101

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+ e- > hadrons

Measurement of the cross section and spectra for $J/\psi$ production in $e^+e^-$ collisions at $\sqrt{s}=10.6\,$GeV.

Source code:BELLE_2009_I811289.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief BELLE J/psi production class BELLE_2009_I811289 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2009_I811289);


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

/// Book histograms and initialise projections before the run
void init() {
  declare("FS", FinalState());
  declare("CFS", FinalState());
  // book histos
  for (unsigned int ix = 0; ix < 5; ++ix) {
    book(_h_spect[ix], 2, 1, 1 + ix);
  }
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h_sigma[ix], 1, 1, 1 + ix);
    for (unsigned int iy = 0; iy < 3; ++iy) {
      book(_h_angle[ix][iy], 3, 1 + ix, 1 + iy);
    }
  }
}

void plotHelicityAngle(const Particle& p, Histo1DPtr h) {
  if (p.children().size() != 2) return;
  if (p.children()[0].abspid() != PID::MUON || p.children()[0].pid() != -p.children()[1].pid()) return;
  Vector3 axis = p.p3().unit();
  const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
  for (const Particle& child : p.children()) {
    if (child.pid() != PID::MUON) continue;
    h->fill(axis.dot(boost.transform(child.mom()).p3().unit()));
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // 4 charged particle veto
  if (apply<FinalState>(event, "CFS").particles().size() < 4) vetoEvent;
  // find the charmonium
  Particles D, Jpsi_direct, Jpsi_feed, onium;
  for (const Particle& p : apply<FinalState>(event, "FS").particles()) {
    Particle parent = p.parents()[0], Jpsi;
    while (!parent.parents().empty()) {
      // charm mesons
      if (parent.abspid() == 411 || parent.abspid() == 421 || parent.abspid() == 431) {
        break;
      }
      // c cbar mesons
      if ((parent.abspid() % 1000) / 10 == 44) {
        if ((parent.parents()[0].abspid() % 1000) / 10 != 44) break;
        if (parent.pid() == 443) Jpsi = parent;
      }
      parent = parent.parents()[0];
    }
    // charm
    if (parent.abspid() == 411 || parent.abspid() == 421 || parent.abspid() == 431) {
      bool found = false;
      for (auto& p : D) {
        // D already in list
        if (fuzzyEquals(p.mom(), parent.mom())) {
          found = true;
          break;
        }
      }
      if (!found) D.push_back(parent);
    }
    // c cbar
    else if ((parent.abspid() % 1000) / 10 == 44) {
      if (parent.pid() == 443) {
        bool found = false;
        for (const auto& p : Jpsi_direct) {
          // psi already in list
          if (fuzzyEquals(p.mom(), parent.mom())) {
            found = true;
            break;
          }
        }
        if (!found) Jpsi_direct.push_back(parent);
      }
      else {
        bool found = false;
        for (const auto& p : onium) {
          // psi already in list
          if (fuzzyEquals(p.mom(), parent.mom())) {
            found = true;
            break;
          }
        }
        if (!found) onium.push_back(parent);
      }
    }
    if (Jpsi.pid() == 443) {
      bool found = false;
      for (const auto& p : Jpsi_feed) {
        // psi already in list
        if (fuzzyEquals(p.mom(), Jpsi.mom())) {
          found = true;
          break;
        }
      }
      if (!found) Jpsi_feed.push_back(Jpsi);
    }
  }
  if (Jpsi_feed.empty() && Jpsi_direct.empty()) vetoEvent;
  // cross sections first
  if (D.empty() && onium.empty() && Jpsi_direct.size() == 1) {
    _h_sigma[1]->fill("10.6"s);
    for (const Particle& p : Jpsi_direct) {
      double modp = p.p3().mod();
      _h_spect[4]->fill(modp);
      plotHelicityAngle(p, _h_angle[0][2]);
      _h_angle[1][2]->fill(abs(p.p3().z() / modp));
    }
  }
  else {
    _h_sigma[0]->fill("10.6"s);
    for (const Particle& p : Jpsi_direct) {
      double modp = p.p3().mod();
      _h_spect[3]->fill(modp);
      plotHelicityAngle(p, _h_angle[0][1]);
      _h_angle[1][1]->fill(abs(p.p3().z() / modp));
    }
    for (const Particle& p : Jpsi_feed) {
      double modp = p.p3().mod();
      _h_spect[3]->fill(modp);
      plotHelicityAngle(p, _h_angle[0][1]);
      _h_angle[1][1]->fill(abs(p.p3().z() / modp));
    }
    if (!D.empty()) {
      for (const Particle& p : Jpsi_direct) {
        _h_spect[1]->fill(p.p3().mod());
      }
      for (const Particle& p : Jpsi_feed) {
        _h_spect[1]->fill(p.p3().mod());
      }
    }
    else {
      for (const Particle& p : Jpsi_direct) {
        _h_spect[2]->fill(p.p3().mod());
      }
      for (const Particle& p : Jpsi_feed) {
        _h_spect[2]->fill(p.p3().mod());
      }
    }
  }
  for (const Particle& p : Jpsi_direct) {
    double modp = p.p3().mod();
    _h_spect[0]->fill(modp);
    plotHelicityAngle(p, _h_angle[0][0]);
    _h_angle[1][0]->fill(abs(p.p3().z() / modp));
  }
  for (const Particle& p : Jpsi_feed) {
    double modp = p.p3().mod();
    _h_spect[0]->fill(modp);
    plotHelicityAngle(p, _h_angle[0][0]);
    _h_angle[1][0]->fill(abs(p.p3().z() / modp));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_spect, crossSection() / sumOfWeights() / femtobarn);
  for (unsigned int ix = 0; ix < 2; ++ix) {
    scale(_h_sigma[ix], crossSection() / sumOfWeights() / picobarn);
    normalize(_h_angle[ix], 1.0, false);
  }
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _h_sigma[2];
Histo1DPtr _h_spect[5], _h_angle[2][3];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2009_I811289);

} ```