Rivet analyses

title: OPAL_1995_I382219

Scaled energy distribution of $D^*$ with flavour separation at LEP

Experiment: OPAL (LEP)

Inspire ID: 382219

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C67 (1995) 27-44, 1995

Beams: e+ e-

Beam energies: (45.6, 45.6)GeV

Run details: - Hadronic $Z$ decays at 91.2~GeV.

The scaled energy distribution of $D^{*\pm}$ is measure, including separating the contributions from $c\bar{c}$ and $b\bar{b}$ events.

Source code:OPAL_1995_I382219.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D* production class OPAL_1995_I382219 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(OPAL_1995_I382219);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(Beam(), "Beams");
  declare(UnstableParticles(), "UFS");

  book(_h_Xe_Ds, 3, 1, 1);
  book(_h_Xe_Ds_b, 4, 1, 1);
  book(_h_Xe_Ds_c, 5, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");

  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
  const double meanBeamMom = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0 / GeV;
  // check if b hadrons or not
  unsigned int nB = (select(ufs.particles(), isBottomHadron)).size();
  // Accept all D*+- decays.
  for (const Particle& p : select(ufs.particles(), Cuts::abspid == PID::DSTARPLUS)) {
    // Scaled energy.
    const double energy = p.E() / GeV;
    const double scaledEnergy = energy / meanBeamMom;
    _h_Xe_Ds->fill(scaledEnergy);
    if (nB == 0)
      _h_Xe_Ds_c->fill(scaledEnergy);
    else
      _h_Xe_Ds_b->fill(scaledEnergy);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // brs for D*+/- -> D0 pi+/- and D0->K+pi-
  double br = 0.677 * 0.03950;
  scale(_h_Xe_Ds, 1. / sumOfWeights() * br);
  scale(_h_Xe_Ds_b, 1. / sumOfWeights() * br);
  scale(_h_Xe_Ds_c, 1. / sumOfWeights() * br);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_Xe_Ds, _h_Xe_Ds_b, _h_Xe_Ds_c;
/// @}

};

RIVET_DECLARE_PLUGIN(OPAL_1995_I382219);

} ```