Rivet analyses

Production and decay of Ξc0 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 Υ(4S) resonance, with CoM boosts of 8.0GeV(e−) and 3.5GeV(e+)

Analysis of Ξc0 production in B decays and from the cc̄ continuum, with the Ξc0 decaying into Ω−K+ and Ξ−π+ final states measured using 116.1 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

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

namespace Rivet {


  /// @brief BABAR Xi_c baryons from fragmentation
  ///
  /// @author Peter Richardson
  class BABAR_2005_I679961 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I679961);


    void init() {
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");
      book(_histOnResonanceA, 1,1,1);
      book(_histOnResonanceB, 2,1,1);
      book(_histOffResonance, 2,1,2);
      book(_sigma,            3,1,1);
    }


    void analyze(const Event& e) {
      // Loop through unstable FS particles and look for charmed mesons/baryons
      const UnstableParticles& ufs = apply<UnstableParticles>(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);

      for (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;
        MSG_DEBUG("mom = " << mom);
        // off-resonance cross section
        if (checkDecay(p.genParticle())) {
          if (onresonance) {
            _histOnResonanceA->fill(mom);
            _histOnResonanceB->fill(mom);
          }
          else {
            _histOffResonance->fill(mom,s/sqr(10.58));
            _sigma->fill(Ecm);
          }
        }
      }
    }


    void finalize() {
      scale(_histOnResonanceA, crossSection()/femtobarn/sumOfWeights()*0.2);
      scale(_histOnResonanceB, crossSection()/femtobarn/sumOfWeights()*0.45);
      scale(_histOffResonance, crossSection()/femtobarn/sumOfWeights()*0.45);
      scale(_sigma           , crossSection()/femtobarn/sumOfWeights());
    }


  private:

    /// @name Histograms
    /// @{
    Histo1DPtr _histOnResonanceA;
    Histo1DPtr _histOnResonanceB;
    Histo1DPtr _histOffResonance;
    BinnedHistoPtr<string> _sigma;
    const string Ecm = "10.58";
    /// @}


    bool checkDecay(ConstGenParticlePtr 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(ConstGenParticlePtr p,
                           unsigned int& nstable,
                           unsigned int& npip, unsigned int& npim,
                           unsigned int& nXip, unsigned int& nXim) {
      ConstGenVertexPtr dv = p->end_vertex();
      /// @todo Use better looping
      for (ConstGenParticlePtr pp: HepMCUtils::particles(dv, Relatives::CHILDREN)){
        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;
        }
      }
    }

  };


  RIVET_DECLARE_ALIASED_PLUGIN(BABAR_2005_I679961, BABAR_2005_S6181155);

}

Aliases: - BABAR_2005_S6181155