Rivet analyses

Cross sections for e⁺e⁻ → π⁺π⁻4π⁰ and e⁺e⁻ → π⁺π⁻3π⁰η between threshold and 4.5 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 1938254

Status: VALIDATED

Authors: - Peter Richardson

References: - 2110.00823

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons

Cross sections for e⁺e⁻ → π⁺π⁻4π⁰ and e⁺e⁻ → π⁺π⁻3π⁰η between threshold and 4.5 GeV measured by BaBar using radiative return. The contributions of the ηπ⁺π⁻π⁰, ηω, ωπ⁰π⁰π⁰ intermediate states are also measured. Useful to compare hadronization and other non-perturbative models at low energies between 1.4 and 4.5 GeV.

Source code:`BABAR_2021_I1938254.cc`

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

namespace Rivet {


  /// @brief e+e- > pi+pi-4pi0 and pi+pi-3pi0 eta
  class BABAR_2021_I1938254 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2021_I1938254);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      // Histograms
      for (unsigned int ix = 0; ix < 5; ++ix) {
        book(_num[ix], "TMP/num_" + to_string(ix));
      }
    }

    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;
      }
      // stable final state
      if (nCount[211] == 1 && nCount[-211] == 1 && nCount[111] == 4) _num[0]->fill();
      // intermediate states
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      for (const Particle& p : ufs.particles(Cuts::pid == 221 || Cuts::pid == 223)) {
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        // eta +X
        int idOther;
        if (p.pid() == 221) {
          idOther = 223;
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first) == 211 || val.first == -211) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.first == 111) {
              // 1 or 3 pi0
              if (val.second != 3 && val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            if (nRes[111] == 1)
              _num[1]->fill();
            else
              _num[4]->fill();
          }
        }
        // omega+X
        else {
          idOther = 221;
          // omega+ 3pi0
          bool matched = true;
          for (const auto& val : nRes) {
            if (abs(val.first) == 111) {
              if (val.second != 3) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _num[3]->fill();
          }
        }
        for (const Particle& p2 : ufs.particles(Cuts::pid == idOther)) {
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          findChildren(p2, nResB, ncountB);
          if (ncountB != 0) continue;
          bool matched2 = true;
          for (const auto& val : nResB) {
            if (val.second != 0) {
              matched2 = false;
              break;
            }
          }
          if (matched2) {
            _num[2]->fill();
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / nanobarn / sumOfWeights();
      for (unsigned int ix = 0; ix < 5; ++ix) {
        double sigma = _num[ix]->val() * fact;
        double error = _num[ix]->err() * fact;
        Estimate1DPtr mult;
        book(mult, 1 + ix, 1, 1);
        for (auto& b : mult->bins()) {
          if (inRange(sqrtS() / GeV, b.xMin(), b.xMax())) {
            b.set(sigma, error);
          }
        }
      }
    }

    ///@}


    /// @name Histograms
    ///@{
    CounterPtr _num[5];
    ///@}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2021_I1938254);

}

Rivet analyses

Cross sections for e+e− → π+π−4π0 and e+e− → π+π−3π0η between threshold and 4.5 GeV

Source code:BABAR_2021_I1938254.cc

Cross sections for e⁺e⁻ → π⁺π⁻4π⁰ and e⁺e⁻ → π⁺π⁻3π⁰η between threshold and 4.5 GeV

Source code:`BABAR_2021_I1938254.cc`