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BABAR_2005_I679961

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 modified 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_I679961.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief BABAR Xi_c baryons from fragmentation
 10  ///
 11  /// @author Peter Richardson
 12  class BABAR_2005_I679961 : public Analysis {
 13  public:
 14
 15    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I679961);
 16
 17
 18    void init() {
 19      declare(Beam(), "Beams");
 20      declare(UnstableParticles(), "UFS");
 21      book(_histOnResonanceA, 1,1,1);
 22      book(_histOnResonanceB, 2,1,1);
 23      book(_histOffResonance, 2,1,2);
 24      book(_sigma,            3,1,1);
 25    }
 26
 27
 28    void analyze(const Event& e) {
 29      // Loop through unstable FS particles and look for charmed mesons/baryons
 30      const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");
 31
 32      const Beam beamproj = apply<Beam>(e, "Beams");
 33      const ParticlePair& beams = beamproj.beams();
 34      const FourMomentum mom_tot = beams.first.momentum() + beams.second.momentum();
 35      const LorentzTransform cms_boost = LorentzTransform::mkFrameTransformFromBeta(mom_tot.betaVec());
 36      const double s = sqr(beamproj.sqrtS());
 37
 38      const bool onresonance = fuzzyEquals(beamproj.sqrtS()/GeV, 10.58, 2E-3);
 39
 40      for (const Particle& p : ufs.particles()) {
 41        // 3-momentum in CMS frame
 42
 43        const double mom = cms_boost.transform(p.momentum()).vector3().mod();
 44        // Only looking at Xi_c^0
 45        if (p.abspid() != 4132 ) continue;
 46        MSG_DEBUG("mom = " << mom);
 47        // off-resonance cross section
 48        if (checkDecay(p.genParticle())) {
 49          if (onresonance) {
 50            _histOnResonanceA->fill(mom);
 51            _histOnResonanceB->fill(mom);
 52          }
 53          else {
 54            _histOffResonance->fill(mom,s/sqr(10.58));
 55            _sigma->fill(Ecm);
 56          }
 57        }
 58      }
 59    }
 60
 61
 62    void finalize() {
 63      scale(_histOnResonanceA, crossSection()/femtobarn/sumOfWeights()*0.2);
 64      scale(_histOnResonanceB, crossSection()/femtobarn/sumOfWeights()*0.45);
 65      scale(_histOffResonance, crossSection()/femtobarn/sumOfWeights()*0.45);
 66      scale(_sigma           , crossSection()/femtobarn/sumOfWeights());
 67    }
 68
 69
 70  private:
 71
 72    /// @name Histograms
 73    /// @{
 74    Histo1DPtr _histOnResonanceA;
 75    Histo1DPtr _histOnResonanceB;
 76    Histo1DPtr _histOffResonance;
 77    BinnedHistoPtr<string> _sigma;
 78    const string Ecm = "10.58";
 79    /// @}
 80
 81
 82    bool checkDecay(ConstGenParticlePtr p) {
 83      unsigned int nstable = 0, npip = 0, npim = 0;
 84      unsigned int nXim = 0, nXip = 0;
 85      findDecayProducts(p, nstable, npip, npim, nXip, nXim);
 86      int id = p->pdg_id();
 87      // Xi_c
 88      if (id == 4132) {
 89        if (nstable == 2 && nXim == 1 && npip == 1) return true;
 90      }
 91      else if (id == -4132) {
 92        if (nstable == 2 && nXip == 1 && npim == 1) return true;
 93      }
 94      return false;
 95    }
 96
 97
 98    void findDecayProducts(ConstGenParticlePtr p,
 99                           unsigned int& nstable,
100                           unsigned int& npip, unsigned int& npim,
101                           unsigned int& nXip, unsigned int& nXim) {
102      ConstGenVertexPtr dv = p->end_vertex();
103      /// @todo Use better looping
104      for (ConstGenParticlePtr pp: HepMCUtils::particles(dv, Relatives::CHILDREN)){
105        int id = pp->pdg_id();
106        if (id==3312) {
107          ++nXim;
108          ++nstable;
109        } else if (id == -3312) {
110          ++nXip;
111          ++nstable;
112        } else if(id == 111 || id == 221) {
113          ++nstable;
114        } else if (pp->end_vertex()) {
115          findDecayProducts(pp, nstable, npip, npim, nXip, nXim);
116        } else {
117          if     (id !=    22) ++nstable;
118          if     (id ==   211) ++npip;
119          else if(id ==  -211) ++npim;
120        }
121      }
122    }
123
124  };
125
126
127  RIVET_DECLARE_ALIASED_PLUGIN(BABAR_2005_I679961, BABAR_2005_S6181155);
128
129}