Rivet analyses

π⁺π⁻ mass distribution in Y(4260) → J/ψπ⁺π⁻

Experiment: BABAR (PEP-II)

Inspire ID: 686354

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 95 (2005) 142001

Beams: * *

Beam energies: ANY

Run details: - Any process producing psi(4230) for decays

Mass distribution in Y(4260) → J/ψπ⁺π⁻ decays (Y(4260) is now ψ(4230)). The background subtracted data were read from figure 3 in the paper. There is no consensus as to the nature of the ψ(4230) cc̄ state and therefore we taken its PDG code to be 9030443, i.e. the first unused code for an undetermined spin one cc̄ state. This can be changed using the PID option if a different code is used by the event generator performing the simulation.

Source code:`BABAR_2005_I686354.cc`

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

namespace Rivet {


  /// @brief Y(4260) -> pi+ pi_ J/psi
  class BABAR_2005_I686354 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I686354);


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

    /// Book histograms and initialise projections before the run
    void init() {
      _pid = getOption<int>("PID", 9030443);
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == _pid);
      declare(ufs, "UFS");
      DecayedParticles PSI(ufs);
      PSI.addStable(443);
      declare(PSI, "PSI");
      // histograms
      book(_h, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {443, 1}};
      DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
      for (unsigned int ix = 0; ix < PSI.decaying().size(); ++ix) {
        if (!PSI.modeMatches(ix, 3, mode)) continue;
        const Particle& pip = PSI.decayProducts()[ix].at(211)[0];
        const Particle& pim = PSI.decayProducts()[ix].at(-211)[0];
        double mpipi = (pip.momentum() + pim.momentum()).mass();
        _h->fill(mpipi);
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    int _pid;
    Histo1DPtr _h;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2005_I686354);

}

Rivet analyses

π+π− mass distribution in Y(4260) → J/ψπ+π−

Source code:BABAR_2005_I686354.cc

π⁺π⁻ mass distribution in Y(4260) → J/ψπ⁺π⁻

Source code:`BABAR_2005_I686354.cc`