Rivet analyses

Cross section for e+e− → hb(n = 1, 2)π+π− at energies between 10.77 and 11.02 GeV

Experiment: BELLE (KEKB)

Inspire ID: 1389855

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 117 (2016) no.14, 142001

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for e+e− → hb(n = 1, 2)π+π− at energies between 10.77 and 11.02 GeV by BELLE.

Source code:BELLE_2016_I1389855.cc

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

namespace Rivet {


  /// @brief e+ e- > hb pi+pi-
  class BELLE_2016_I1389855 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2016_I1389855);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::pid==10553 ||
                                Cuts::pid==110553), "UFS");

      book(_nhb1, 1, 1, 3);
      book(_nhb2, 1, 1, 4);

      // Check which indices match the Ecm energy
      YODA::BinnedEstimate<int> tmp = refData<YODA::BinnedEstimate<int>>(1, 1, 1); 
      for (const auto& est : tmp.bins()) {
        if (abs(sqrtS()/MeV-est.val())<est.totalErrAvg()) {
          edges.push_back(est.xEdge());
        }
      }
      if (edges.empty())
        MSG_ERROR("Beam energy incompatible with analysis.");
    }

    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;
        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) {
          for (const int Ecm : edges) {
            if (p.pid() == 10553) {
              _nhb1->fill(Ecm);
            }
            else {
              _nhb2->fill(Ecm);
            }
          }
          break;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      const double sf = crossSection()/sumOfWeights()/picobarn;
      scale({_nhb1, _nhb2}, sf);
    }
    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<int> _nhb1, _nhb2;
    vector<int> edges;
    /// @}

  };

  RIVET_DECLARE_PLUGIN(BELLE_2016_I1389855);
}