Rivet analyses

Cross section for hadron production for $\sqrt{s}=3.65\to3.87\,$GeV

Experiment: BESII (BEPC)

Inspire ID: 717720

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 121801

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- > hadrons

Measurement of the cross section for $e^+e^-\to\text{hadrons}$ for $\sqrt{s}=3.65\to3.87\,$GeV. In addition the cross section to charm hadrons near the $\psi(3770)$ is measured. As the analyses requires the beam energy smearing described in the paper then central CMS energy should be specified using the ECENT (in GeV) option.

Source code:BESII_2006_I717720.cc

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

namespace Rivet {


  /// @brief e+ e- > hadrons
  class BESII_2006_I717720 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I717720);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(UnstableParticles(Cuts::abspid == 411 || Cuts::abspid == 421), "UFS");
      declare(FinalState(), "FS");

      // Book histograms
      book(_sigma[0], 1, 1, 1);
      for (unsigned int ix = 1; ix < 4; ++ix) book(_sigma[ix], 2, 1, ix);
      string eCent = getOption<string>("ECENT", std::to_string(sqrtS() / GeV));
      double ee = std::stod(eCent);
      for (unsigned int ix = 0; ix < 3; ++ix) {
        for (const auto& en : _sigma[ix].binning().edges<0>()) {
          if (fuzzyEquals(std::stod(en), ee, 1e-5)) {
            _ecms[ix] = en;
            break;
          }
        }
      }
      if (_ecms[0].empty() && _ecms[1].empty() && _ecms[2].empty())
        MSG_ERROR("Beam energy incompatible with analysis.");
      _ecms[3] = _ecms[2];
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const FinalState& fs = apply<FinalState>(event, "FS");
      const FinalState& ufs = apply<FinalState>(event, "UFS");
      map<long, int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      // mu+mu- + photons
      if (nCount[-13] == 1 and nCount[13] == 1 && ntotal == 2 + nCount[22]) {
        vetoEvent;
      }
      else if (nCount[-11] == 1 and nCount[11] == 1 && ntotal == 2 + nCount[22]) {
        vetoEvent;
      }
      // everything else
      else {
        if (!_ecms[0].empty()) _sigma[0]->fill(_ecms[0]);
        if (!ufs.particles().empty()) {
          if (!_ecms[1].empty()) _sigma[1]->fill(_ecms[1]);
          if (ufs.particles()[0].abspid() == 421) {
            if (!_ecms[2].empty()) _sigma[2]->fill(_ecms[2]);
          }
          else {
            if (!_ecms[3].empty()) _sigma[3]->fill(_ecms[3]);
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection() / sumOfWeights() / nanobarn;
      for (unsigned int ix = 0; ix < 4; ++ix) scale(_sigma[ix], fact);
    }

    /// @}

    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _sigma[4];
    string _ecms[4];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESII_2006_I717720);

}