Rivet analyses

Ds± and Ds*± spectra in the continuum near the Υ(4S)

Experiment: CLEO (CESR)

Inspire ID: 526554

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D62 (2000) 072003, 2000

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+e− analysis near the Υ(4S) resonance

Analysis of charm quark fragmentation at 10.5 GeV, based on a data sample of 103 fb collected by the CLEO experiment. Fragmentation into Ds± and Ds*± mesons is studied. This analysis can be used to constrain charm fragmentation in Monte Carlo generators. The branching ratios B1 = B(Ds*+ → Ds+γ)B(Ds+ → ϕπ+)B(ϕ → K+K−) and B2 = B(Ds+ → ϕπ+)B(ϕ → K+K−), are not unfolded.

Source code:CLEO_2000_I526554.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class CLEO_2000_I526554 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_2000_I526554);


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

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

      // Book histograms
      book(_h_Ds_star1, 1, 1, 1);
      book(_h_Ds, 2, 1, 1);
      book(_h_Ds_star2, 3, 1, 1);
      book(_h_Ds_primary, 4, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Loop through unstable FS particles and look for charmed mesons
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");

      const Beam beamproj = apply<Beam>(event, "Beams");
      const ParticlePair& beams = beamproj.beams();
      const FourMomentum mom_tot = beams.first.momentum() + beams.second.momentum();
      LorentzTransform cms_boost;
      if (mom_tot.p3().mod() > 1 * MeV)
        cms_boost = LorentzTransform::mkFrameTransformFromBeta(mom_tot.betaVec());
      const double s = sqr(beamproj.sqrtS());
      for (const Particle& p : ufs.particles(Cuts::abspid == 431 or Cuts::abspid == 433)) {
        // 3-momentum in CMS frame
        const double mom = cms_boost.transform(p.momentum()).vector3().mod();
        const int pdgid = p.abspid();
        double mH2(0.), xp(0.);
        bool primary = true;
        switch (pdgid) {
          case 431:
            //   MSG_DEBUG("D_s found");
            mH2 = sqr(1.96834);
            xp = mom / sqrt(s / 4.0 - mH2);
            _h_Ds->fill(xp);
            for (const Particle& mother : p.parents()) {
              if (PID::isCharmMeson(mother.pid())) {
                primary = false;
                break;
              }
            }
            if (primary) _h_Ds_primary->fill(xp);
            break;
          case 433:
            MSG_DEBUG("D_s* found");
            mH2 = sqr(2.1122);
            xp = mom / sqrt(s / 4.0 - mH2);
            _h_Ds_star1->fill(xp);
            _h_Ds_star2->fill(xp);
            break;
          default: break;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      // BR(D_s->phi pi) x BR(phi->K+K-)
      double br2 = 0.0227;
      // x D_s* -> gamma d_s
      double br1 = br2 * .935;
      // cross section factor
      double fact = crossSection() / picobarn / sumOfWeights();
      // normalize the cross sections (bin width)
      scale(_h_Ds_star1, br1 * fact * 0.03);
      scale(_h_Ds, br2 * fact * 0.03);
      scale(_h_Ds_star2, br2 * fact * 0.03);
      scale(_h_Ds_primary, br2 * fact * 0.03);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Ds, _h_Ds_primary, _h_Ds_star1, _h_Ds_star2;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CLEO_2000_I526554);


}