Rivet analyses

Cross section for e+e− → J/ψX(3940), X(4160) at $\sqrt{s}=10.6\,$GeV

Experiment: BELLE (KEKB)

Inspire ID: 759262

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 100 (2008) 202001

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+e- -> J/psi X(3940) X(4160)

Cross section for e+e− → J/ψX(3940)/X(4160) at $\sqrt{s}=10.6\,$GeV. The X(3940) is measured using D*D̄ modes while the X(4160) mode is measured using D*D̄* modes. The status of the X(3940) is not clear, we take the PDG code to be 9010441, which can be changed using the PID3940 option. For the X(4160) spin, partiy, 2− is favoured and therefore we use 9010445, which can be changed using the PID4160 option.

Source code:BELLE_2008_I759262.cc

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

namespace Rivet {


  /// @brief e+e- > J/psi X(3940) or X(4160)
  class BELLE_2008_I759262 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I759262);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // set the PDG code
      _pid[0] = getOption<int>("PID3940", 9010441);
      _pid[1] = getOption<int>("PID4160", 9010445);
      // projections
      declare("FS", FinalState());
      declare("UFS", UnstableParticles(Cuts::pid == 443 || Cuts::pid == _pid[0] || Cuts::pid == _pid[1]));
      // histograms
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h[ix], 1, 1, 1 + ix);
      }
    }

    void findChildren(const Particle& p, map<long, int>& nRes, int& ncount, unsigned int& nCharged) {
      for (const Particle& child : p.children()) {
        if (child.children().empty()) {
          --nRes[child.pid()];
          --ncount;
          if (PID::isCharged(p.pid())) ++nCharged;
        }
        else {
          findChildren(child, nRes, ncount, nCharged);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // final state particles
      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;
      }
      // loop over J/psi
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      bool matched = false;
      for (const Particle& p : ufs.particles(Cuts::pid == 443)) {
        if (p.children().empty()) continue;
        map<long, int> nRes = nCount;
        int ncount = ntotal;
        unsigned int nCharged = 0;
        findChildren(p, nRes, ncount, nCharged);
        // X(3940)/X(4160)
        for (const Particle& p2 : ufs.particles(Cuts::pid != 443)) {
          map<long, int> nResB = nRes;
          int ncountB = ncount;
          unsigned int nChargedB = 0;
          findChildren(p2, nResB, ncountB, nChargedB);
          if (ncountB != 0) continue;
          matched = true;
          for (const auto& val : nResB) {
            if (val.second != 0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            if (p2.children().size() != 2) break;
            if (p2.children()[0].pid() * p2.children()[1].pid() > 0) break;
            if (p2.pid() == _pid[0]) {
              if ((p2.children()[0].abspid() == 413 && p2.children()[1].abspid() == 411)
                  || (p2.children()[1].abspid() == 413 && p2.children()[0].abspid() == 411)
                  || (p2.children()[0].abspid() == 423 && p2.children()[1].abspid() == 421)
                  || (p2.children()[1].abspid() == 423 && p2.children()[0].abspid() == 421))
                _h[0]->fill("10.6"s);
            }
            else {
              if (p2.children()[0].pid() == -p2.children()[1].pid()
                  && (p2.children()[0].abspid() == 413 || p2.children()[0].abspid() == 423))
                _h[1]->fill("10.6"s);
            }
            break;
          }
        }
        if (matched) break;
      }
    }


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

    /// @}


    /// @name Histograms
    /// @{
    int _pid[2];
    BinnedHistoPtr<string> _h[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2008_I759262);

}