Rivet analyses

Cross sections for e⁺e⁻ → 2π⁺2π⁻3π⁰ and 2π⁺2π⁻2π⁰η from threshold to 4.5 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 1844422

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2102.01314

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross sections for e⁺e⁻ → 2π⁺2π⁻3π⁰ and 2π⁺2π⁻2π⁰η from threshold to 4.5 GeV by BaBar. The 2π⁺2π⁻η, ωπ⁰η, π⁺π⁻2π⁰ω, π⁺π⁻2π⁰η resonant subprocesses are also measured.

Source code:`BABAR_2021_I1844422.cc`

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

namespace Rivet {


  /// @brief e+e- > 2pi+ 2pi- 3pi0 and  2pi+ 2pi- 2pi0 eta
  class BABAR_2021_I1844422 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2021_I1844422);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_c_2pip2pim3pi0, "TMP/2pip2pim3pi0");
      book(_c_2pip2pimeta, "TMP/2pip2pimeta");
      book(_c_omegapi0eta, "TMP/omegapi0eta");
      book(_c_pippim2pi0omega, "TMP/pippim2pi0omega");
      book(_c_pippim2pi0eta, "TMP/pippim2pi0eta");
      book(_c_2pip2pim2pi0eta, "TMP/2pip2pim2pi0eta");
    }

    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;
      }
      if (ntotal == 7 && nCount[211] == 2 && nCount[-211] == 2 && nCount[111] == 3) _c_2pip2pim3pi0->fill();
      // intermediate omega and eta mesons
      Particles unstable = apply<FinalState>(event, "UFS").particles(Cuts::pid == 223 or Cuts::pid == 221);
      for (const Particle& p : unstable) {
        if (p.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p, nRes, ncount);
        // eta
        if (p.pid() == 221) {
          if (ncount == 4) {
            // 2pi+2pi- eta
            if (nRes[211] == 2 && nRes[-211] == 2) {
              _c_2pip2pimeta->fill();
            }
            // pi+pi- 2pi0 eta
            else if (nRes[211] == 1 && nRes[-211] == 1 && nRes[111] == 2) {
              _c_pippim2pi0eta->fill();
            }
          }
          else if (ncount == 6) {
            // 2pi+ 2pi- 2pi0 eta
            if (nRes[211] == 2 && nRes[-211] == 2 && nRes[111] == 2) {
              _c_2pip2pim2pi0eta->fill();
            }
          }
        }
        // omega
        else if (p.pid() == 223) {
          // pi+pi- 2pi0 omega
          if (ncount == 4 && nRes[211] == 1 && nRes[-211] == 1 && nRes[111] == 2) {
            _c_pippim2pi0omega->fill();
          }
        }
        // mode with both eta and omega
        // pi0 omega eta
        for (const Particle& p2 : unstable) {
          if (p2.pid() == p.pid()) continue;
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          findChildren(p2, nResB, ncountB);
          if (ncountB != 1) continue;
          bool matched = true;
          for (const auto& val : nResB) {
            if (abs(val.first) == 111) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _c_omegapi0eta->fill();
            break;
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 1; ix < 7; ++ix) {
        double sigma = 0., error = 0.;
        if (ix == 1) {
          sigma = _c_2pip2pim3pi0->val();
          error = _c_2pip2pim3pi0->err();
        }
        else if (ix == 2) {
          sigma = _c_2pip2pimeta->val();
          error = _c_2pip2pimeta->err();
        }
        else if (ix == 3) {
          sigma = _c_omegapi0eta->val();
          error = _c_omegapi0eta->err();
        }
        else if (ix == 4) {
          sigma = _c_pippim2pi0omega->val();
          error = _c_pippim2pi0omega->err();
        }
        else if (ix == 5) {
          sigma = _c_pippim2pi0eta->val();
          error = _c_pippim2pi0eta->err();
        }
        else if (ix == 6) {
          sigma = _c_2pip2pim2pi0eta->val();
          error = _c_2pip2pim2pi0eta->err();
        }
        sigma *= crossSection() / sumOfWeights() / nanobarn;
        error *= crossSection() / sumOfWeights() / nanobarn;
        Estimate1DPtr mult;
        book(mult, ix, 1, 1);
        for (auto& b : mult->bins()) {
          if (inRange(sqrtS() / GeV, b.xMin(), b.xMax())) {
            b.set(sigma, error);
          }
        }
      }
    }

    ///@}


    /// @name Histograms
    ///@{
    CounterPtr _c_2pip2pim3pi0, _c_2pip2pimeta, _c_omegapi0eta, _c_pippim2pi0omega, _c_pippim2pi0eta,
        _c_2pip2pim2pi0eta;
    ///@}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2021_I1844422);

}

Rivet analyses

Cross sections for e+e− → 2π+2π−3π0 and 2π+2π−2π0η from threshold to 4.5 GeV

Source code:BABAR_2021_I1844422.cc

Cross sections for e⁺e⁻ → 2π⁺2π⁻3π⁰ and 2π⁺2π⁻2π⁰η from threshold to 4.5 GeV

Source code:`BABAR_2021_I1844422.cc`