Rivet analyses

ψ(2S) → p̄K+Σ0 and χcJ → p̄K+Λ0

Experiment: BESIII (BEPC)

Inspire ID: 1203840

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 87 (2013) 1, 012007

Beams: * *

Beam energies: ANY

Run details: - Any process producing psi(2S) and chi_c originally e+e-

Measurements of mass distributions in the decays ψ(2S) → p̄K+Σ0 and χcJ → p̄K+Λ0. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:BESIII_2013_I1203840.cc

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

namespace Rivet {


  /// @brief psi(2S) -> pbar K+ Sigma^$ and chi_cJ -> pbar K+Lambda
  class BESIII_2013_I1203840 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1203840);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 20443 or Cuts::pid == 445 or Cuts::pid == 10441
                                                or Cuts::pid == 100443);
      declare(ufs, "UFS");
      DecayedParticles chi(ufs);
      chi.addStable(PID::PI0);
      chi.addStable(PID::K0S);
      chi.addStable(PID::SIGMA0);
      chi.addStable(PID::SIGMA0);
      chi.addStable(PID::LAMBDA);
      chi.addStable(-PID::LAMBDA);
      declare(chi, "chi");
      // histograms
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h_psi[ix], 1, 1, ix + 1);
        for (unsigned int iy = 0; iy < 3; ++iy) book(_h_chi[iy][ix], 2, iy + 1, ix + 1);
      }
      book(_h_pLam, 3, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{-2212, 1}, {3212, 1}, {321, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{2212, 1}, {-3212, 1}, {-321, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{-2212, 1}, {3122, 1}, {321, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{2212, 1}, {-3122, 1}, {-321, 1}};
      DecayedParticles chi = apply<DecayedParticles>(event, "chi");
      // loop over particles
      for (unsigned int ix = 0; ix < chi.decaying().size(); ++ix) {
        int sign = 1;
        if (chi.decaying()[ix].pid() == 100443) {
          if (chi.modeMatches(ix, 3, mode1)) {
            sign = 1;
          }
          else if (chi.modeMatches(ix, 3, mode1CC)) {
            sign = -1;
          }
          else
            continue;
          const Particle& pbar = chi.decayProducts()[ix].at(-sign * 2212)[0];
          const Particle& Kp = chi.decayProducts()[ix].at(sign * 321)[0];
          const Particle& sigma = chi.decayProducts()[ix].at(sign * 3212)[0];
          _h_psi[0]->fill((pbar.momentum() + sigma.momentum()).mass());
          _h_psi[1]->fill((Kp.momentum() + sigma.momentum()).mass());
        }
        else {
          if (chi.modeMatches(ix, 3, mode2)) {
            sign = 1;
          }
          else if (chi.modeMatches(ix, 3, mode2CC)) {
            sign = -1;
          }
          else
            continue;
          unsigned int iloc = chi.decaying()[ix].pid() == 10441 ? 0 : chi.decaying()[ix].pid() == 445 ? 2 : 1;
          const Particle& pbar = chi.decayProducts()[ix].at(-sign * 2212)[0];
          const Particle& Kp = chi.decayProducts()[ix].at(sign * 321)[0];
          const Particle& lam = chi.decayProducts()[ix].at(sign * 3122)[0];
          _h_chi[iloc][0]->fill((pbar.momentum() + Kp.momentum()).mass());
          _h_chi[iloc][1]->fill((Kp.momentum() + lam.momentum()).mass());
          if (iloc == 0) _h_pLam->fill((pbar.momentum() + lam.momentum()).mass());
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) {
        normalize(_h_psi[ix], 1., false);
        for (unsigned int iy = 0; iy < 3; ++iy) normalize(_h_chi[iy][ix], 1., false);
      }
      normalize(_h_pLam, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_psi[2], _h_chi[3][2], _h_pLam;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESIII_2013_I1203840);

}