Rivet analyses

Cross section for e⁺e⁻ → ηπ⁺π⁻ between 1.2 and 3.5 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 1647139

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev. D97 (2018) 052007

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross section for e⁺e⁻ → ηπ⁺π⁻ at energies between 1.2 and 3.5 GeV using radiative events.

Source code:`BABAR_2018_I1647139.cc`

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

namespace Rivet {


  /// @brief Add a short analysis description here
  class BABAR_2018_I1647139 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2018_I1647139);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_numEtaPiPi, "TMP/EtaPiPi");

    }


    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()==221) {
      map<long,int> nRes = nCount;
      int ncount = ntotal;
      findChildren(p,nRes,ncount);
      // eta pi+pi-
      if(ncount!=2) continue;
      bool matched = true;
      for(auto const & val : nRes) {
        if(abs(val.first)==211) {
          if(val.second !=1) {
        matched = false;
        break;
          }
        }
        else if(val.second!=0) {
          matched = false;
          break;
        }
      }
      if(matched)
        _numEtaPiPi->fill();
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      double sigma = _numEtaPiPi->val();
      double error = _numEtaPiPi->err();
      sigma *= crossSection()/ sumOfWeights() /nanobarn;
      error *= crossSection()/ sumOfWeights() /nanobarn;
      Estimate1DPtr  mult;
      book(mult, 1, 1, 1);
      for (auto& b : mult->bins()) {
        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
          b.set(sigma, error);
        }
      }
    }

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BABAR_2018_I1647139);


}

Rivet analyses

Cross section for e+e− → ηπ+π− between 1.2 and 3.5 GeV

Source code:BABAR_2018_I1647139.cc

Cross section for e⁺e⁻ → ηπ⁺π⁻ between 1.2 and 3.5 GeV

Source code:`BABAR_2018_I1647139.cc`