Rivet analyses

title: BABAR_2001_I558091

Inclusive $J/\psi$ cross section at 10.57 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 558091

Status: VALIDATED

Authors: none listed

References: - PRL 87,162002

Beams: e- e+

Beam energies: ANY

Run details: - e+ e- to hadrons

Measurement of inclusive $J/\psi$ production by BaBar for 10.57 GeV.

Source code:BABAR_2001_I558091.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi rate class BABAR_2001_I558091 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2001_I558091);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");
  book(_c_jpsi, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  double nJsi = 0.;
  for (const Particle& p : ufs.particles()) {
    if (p.pid() == 443) {
      bool fs = true;
      for (const Particle& child : p.children()) {
        if (child.pid() == 443) {
          fs = false;
          break;
        }
      }
      if (fs) nJsi += 1.;
    }
  }
  _c_jpsi->fill(Ecm, nJsi);
}


/// Normalise histograms etc., after the run
void finalize() {
  const double fact = crossSection() / sumOfWeights() / picobarn;
  scale(_c_jpsi, fact);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<string> _c_jpsi;
const string Ecm = "10.57";
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2001_I558091);

} ```