Rivet analyses

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*± is measure, including separating the contributions from cc̄ and bb̄ events.

Source code:OPAL_1995_I382219.cc

// -*- 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);


}