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(auto const & 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`