Rivet analyses

Cross section for e⁺e⁻ → J/ψπ⁺π⁻ at energies between 3.8 and 4.82 GeV

Experiment: BELLE (KEKB)

Inspire ID: 1225975

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 110 (2013) 252002, 2013

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for e⁺e⁻ → J/ψπ⁺π⁻ at energies between 3.8 and 4.82 GeV using radiative return by BELLE.

Source code:`BELLE_2013_I1225975.cc`

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

namespace Rivet {


  /// @brief e+ e- > pi+ pi- J/Psi
  class BELLE_2013_I1225975 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1225975);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nJPsi, "TMP/jpsi");
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for (const Particle &child : p.children()) {
        if (child.children().empty()) {
          --nRes[child.pid()];
          --ncount;
        }
        else {
          findChildren(child,nRes,ncount);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      map<long,int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        // find the omega
        if (p.pid()==443) {
          map<long,int> nRes = nCount;
          int ncount = ntotal;
          findChildren(p,nRes,ncount);
          // omega pi+pi-
          if (ncount!=2) continue;
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first)==211) {
              if (val.second !=1) {
                matched = false;
                break;
              }
            }
            else if (val.second!=0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _nJPsi->fill();
            break;
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_nJPsi, crossSection()/ sumOfWeights() /picobarn);
      Estimate1DPtr  mult;
      book(mult, 1, 1, 1);
      for (auto& b : mult->bins()) {
        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
          b.set(_nJPsi->val(), _nJPsi->err());
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    CounterPtr _nJPsi;
    /// @}


  };

  RIVET_DECLARE_PLUGIN(BELLE_2013_I1225975);

}

Rivet analyses

Cross section for e+e− → J/ψπ+π− at energies between 3.8 and 4.82 GeV

Source code:BELLE_2013_I1225975.cc

Cross section for e⁺e⁻ → J/ψπ⁺π⁻ at energies between 3.8 and 4.82 GeV

Source code:`BELLE_2013_I1225975.cc`