Rivet analyses

ψ(2S) → pn̄π⁻ and np̄π⁺

Experiment: BESII (BEPC)

Inspire ID: 716589

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 74 (2006) 012004

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decays ψ(2S) → pn̄π⁻ and np̄π⁺. The data were read from the plots in the paper and may not be corrected for efficiency or background.

Source code:`BESII_2006_I716589.cc`

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

namespace Rivet {


  /// @brief psi(2S) -> p nbar pi+ + c.c
  class BESII_2006_I716589 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I716589);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 100443);
      declare(ufs, "UFS");
      DecayedParticles psi(ufs);
      psi.addStable(PID::PI0);
      psi.addStable(PID::K0S);
      psi.addStable(PID::ETA);
      psi.addStable(PID::ETAPRIME);
      declare(psi, "psi");
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h[ix], 1, 1, 1 + ix);
        book(_dalitz[ix], "dalitz_" + toString(ix + 1), 50, 1., 8., 50, 1., 8.);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{2212, 1}, {-2112, 1}, {-211, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-2212, 1}, {2112, 1}, {211, 1}};
      DecayedParticles psi = apply<DecayedParticles>(event, "psi");
      // loop over particles
      for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
        if (psi.modeMatches(ix, 3, mode)) {
          const Particle& pim = psi.decayProducts()[ix].at(-211)[0];
          const Particle& pp = psi.decayProducts()[ix].at(2212)[0];
          const Particle& nbar = psi.decayProducts()[ix].at(-2112)[0];
          double mminus = (pp.momentum() + pim.momentum()).mass2();
          double mplus = (nbar.momentum() + pim.momentum()).mass2();
          _h[0]->fill(sqrt(mminus));
          _h[1]->fill(sqrt(mplus));
          _dalitz[0]->fill(mminus, mplus);
        }
        else if (psi.modeMatches(ix, 3, modeCC)) {
          const Particle& pip = psi.decayProducts()[ix].at(211)[0];
          const Particle& nn = psi.decayProducts()[ix].at(2112)[0];
          const Particle& pbar = psi.decayProducts()[ix].at(-2212)[0];
          double mminus = (pbar.momentum() + pip.momentum()).mass2();
          double mplus = (nn.momentum() + pip.momentum()).mass2();
          _h[0]->fill(sqrt(mminus));
          _h[1]->fill(sqrt(mplus));
          _dalitz[1]->fill(mminus, mplus);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix) {
        normalize(_h[ix]);
        normalize(_dalitz[ix]);
      }
    }
    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    Histo2DPtr _dalitz[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BESII_2006_I716589);

}

Rivet analyses

ψ(2S) → pn̄π− and np̄π+

Source code:BESII_2006_I716589.cc

ψ(2S) → pn̄π⁻ and np̄π⁺

Source code:`BESII_2006_I716589.cc`