Rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BABAR_2005_S6181155

Production and decay of $\Xi^0_c$ at BABAR.
Experiment: BaBar (PEP-II)
Inspire ID: 679961
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 95 (2005) 142003
  • hep-ex/0504014
Beams: e+ e-
Beam energies: (3.5, 8.0); (3.5, 7.9) GeV
Run details:
  • $e^+ e^-$ analysis on the $\Upsilon(4S)$ resonance, with CoM boosts of 8.0 GeV ($e^-$) and 3.5 GeV ($e^+$)

Analysis of $\Xi_c^0$ production in B decays and from the $c\bar{c}$ continuum, with the $\Xi_c^0$ decaying into $\Omega^- K^+$ and $\Xi^- \pi^+$ final states measured using 116.1 $\text{fb}^{-1}$ of data collected by the BABAR detector. The normalisation of the data as been modifed from that presented in the original paper in order to produce a differential cross section rather than the cross section in each bin. In addition to the data presented in the paper plots are alos made with unit normalisation which can be more useful for Monte Carlo tuning.

Source code: BABAR_2005_S6181155.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableFinalState.hh"

namespace Rivet {


  /// @brief BABAR Xi_c baryons from fragmentation
  /// @author Peter Richardson
  class BABAR_2005_S6181155 : public Analysis {
  public:

    BABAR_2005_S6181155()
      : Analysis("BABAR_2005_S6181155")
    { }

    void init() {
      declare(Beam(), "Beams");
      declare(UnstableFinalState(), "UFS");
      _histOnResonanceA = bookHisto1D(1,1,1);
      _histOnResonanceB = bookHisto1D(2,1,1);
      _histOffResonance = bookHisto1D(2,1,2);
      _sigma            = bookHisto1D(3,1,1);
      _histOnResonanceA_norm = bookHisto1D(4,1,1);
      _histOnResonanceB_norm = bookHisto1D(5,1,1);
      _histOffResonance_norm = bookHisto1D(5,1,2);
      
    }

    void analyze(const Event& e) {
      const double weight = e.weight();

      // Loop through unstable FS particles and look for charmed mesons/baryons
      const UnstableFinalState& ufs = apply<UnstableFinalState>(e, "UFS");

      const Beam beamproj = apply<Beam>(e, "Beams");
      const ParticlePair& beams = beamproj.beams();
      const FourMomentum mom_tot = beams.first.momentum() + beams.second.momentum();
      const LorentzTransform cms_boost = LorentzTransform::mkFrameTransformFromBeta(mom_tot.betaVec());
      const double s = sqr(beamproj.sqrtS());

      const bool onresonance = fuzzyEquals(beamproj.sqrtS()/GeV, 10.58, 2E-3);

      foreach (const Particle& p, ufs.particles()) {
        // 3-momentum in CMS frame

        const double mom = cms_boost.transform(p.momentum()).vector3().mod();
        // Only looking at Xi_c^0
        if (p.abspid() != 4132 ) continue;
        if (onresonance) {
          _histOnResonanceA_norm->fill(mom,weight);
          _histOnResonanceB_norm->fill(mom,weight);
        }
        else {
          _histOffResonance_norm->fill(mom,s/sqr(10.58)*weight);
        }
        MSG_DEBUG("mom = " << mom);
        // off-resonance cross section
        if (checkDecay(p.genParticle())) {
          if (onresonance) {
            _histOnResonanceA->fill(mom,weight);
            _histOnResonanceB->fill(mom,weight);
          }
          else {
            _histOffResonance->fill(mom,s/sqr(10.58)*weight);
            _sigma->fill(10.6,weight);
          }
        }
      }
    }


    void finalize() {
      scale(_histOnResonanceA, crossSection()/femtobarn/sumOfWeights());
      scale(_histOnResonanceB, crossSection()/femtobarn/sumOfWeights());
      scale(_histOffResonance, crossSection()/femtobarn/sumOfWeights());
      scale(_sigma           , crossSection()/femtobarn/sumOfWeights());
      normalize(_histOnResonanceA_norm);
      normalize(_histOnResonanceB_norm);
      normalize(_histOffResonance_norm);
    }


  private:

    //@{
    /// Histograms
    Histo1DPtr _histOnResonanceA;
    Histo1DPtr _histOnResonanceB;
    Histo1DPtr _histOffResonance;
    Histo1DPtr _sigma           ;
    Histo1DPtr _histOnResonanceA_norm;
    Histo1DPtr _histOnResonanceB_norm;
    Histo1DPtr _histOffResonance_norm;
    //@}

    bool checkDecay(const GenParticle* p) {
      unsigned int nstable = 0, npip = 0, npim = 0;
      unsigned int nXim = 0, nXip = 0;
      findDecayProducts(p, nstable, npip, npim, nXip, nXim);
      int id = p->pdg_id();
      // Xi_c
      if (id == 4132) {
        if (nstable == 2 && nXim == 1 && npip == 1) return true;
      }
      else if (id == -4132) {
        if (nstable == 2 && nXip == 1 && npim == 1) return true;
      }
      return false;
    }

    void findDecayProducts(const GenParticle* p,
                           unsigned int& nstable,
                           unsigned int& npip, unsigned int& npim,
                           unsigned int& nXip, unsigned int& nXim) {
      const GenVertex* dv = p->end_vertex();
      /// @todo Use better looping
      for (GenVertex::particles_out_const_iterator pp = dv->particles_out_const_begin(); pp != dv->particles_out_const_end(); ++pp) {
        int id = (*pp)->pdg_id();
        if (id==3312) {
          ++nXim;
          ++nstable;
        } else if (id == -3312) {
          ++nXip;
          ++nstable;
        } else if(id == 111 || id == 221) {
          ++nstable;
        } else if ((*pp)->end_vertex()) {
          findDecayProducts(*pp, nstable, npip, npim, nXip, nXim);
        } else {
          if     (id !=    22) ++nstable;
          if     (id ==   211) ++npip;
          else if(id ==  -211) ++npim;
        }
      }
    }

  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(BABAR_2005_S6181155);

}