Rivet analyses

Cross section for e+e− → pK−Λ̄0 + c.c. for $\sqrt{s}$ from 4.009 and 4.951 GeV

Experiment: BESIII (BEPC)

Inspire ID: 2674370

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 12 (2023) 027 - arXiv: 2211.10755

Beams: e+ e-

Beam energies: (2.0, 2.0); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.1, 2.1); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.2, 2.2); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.3, 2.3); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.4, 2.4); (2.5, 2.5); (2.5, 2.5)GeV

Run details: - e+ e- to hadrons

Measurement of the cross section for e+e− → pK−Λ̄0 + c.c. for $\sqrt{s}$ from 4.009 and 4.951 GeV by the BESIII collaboration.

Source code:BESIII_2023_I2674370.cc

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

namespace Rivet {


  /// @brief e+ e- -> p K- Lambdabar +cc
  class BESIII_2023_I2674370 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2674370);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(Cuts::abspid == 3122), "UFS");
      // counter
      book(_sigma, 1, 1, 1);
      for (const string& en : _sigma.binning().edges<0>()) {
        const double eval = stod(en);
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en;
          break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }

    void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) const {
      for (const Particle& child : p.children()) {
        if (child.children().empty()) {
          nRes[child.pid()] -= 1;
          --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");
      // loop over Lambda baryons
      for (const Particle& lam : ufs.particles()) {
        bool matched = false;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        findChildren(lam, nRes, ncount);
        int sign = lam.pid() / lam.abspid();
        if (ncount == 2) {
          matched = true;
          for (const auto& val : nRes) {
            if (val.first == sign * 321 || val.first == -sign * 2212) {
              if (val.second != 1) {
                matched = false;
                break;
              }
            }
            else if (val.second != 0) {
              matched = false;
              break;
            }
          }
        }
        if (matched) {
          _sigma->fill(_sqs);
          break;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_sigma, crossSection() / sumOfWeights() / picobarn);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma;
    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2023_I2674370);

}