Rivet analyses

π+π− mass spectrum in Υ(2S) → π+π−Υ(1S)

Experiment: ARGUS (DORIS)

Inspire ID: 238071

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Z.Phys.C 35 (1987) 283

Beams: * *

Beam energies: ANY

Run details: - In princple any process producing Upsilon(2S)

Measurement of the π+π− mass spectrum in Υ(2S) → π+π−Υ(1S).

Source code:ARGUS_1987_I238071.cc

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

namespace Rivet {


  /// @brief Upsilon(2S) -> Upsilon(1S) pi+pi-
  class ARGUS_1987_I238071 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I238071);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 100553);
      declare(ufs, "UFS");
      DecayedParticles UPS(ufs);
      UPS.addStable(553);
      declare(UPS, "UPS");
      // histos
      for (unsigned int ix = 0; ix < 2; ++ix) {
        book(_h[ix], 1 + ix, 1, 1);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles UPS = apply<DecayedParticles>(event, "UPS");
      // loop over particles
      for (unsigned int ix = 0; ix < UPS.decaying().size(); ++ix) {
        // check pi+pi- upslion(1S) decay mode
        if (!UPS.modeMatches(ix, 3, mode)) continue;
        const Particle& ups1 = UPS.decayProducts()[ix].at(553)[0];
        const Particle& pip = UPS.decayProducts()[ix].at(211)[0];
        const Particle& pim = UPS.decayProducts()[ix].at(-211)[0];
        double mpipi = (pip.momentum() + pim.momentum()).mass();
        _h[0]->fill(mpipi);
        double mpi = pip.mass() + pim.mass();
        double x = (mpipi - mpi) / (UPS.decaying()[ix].mass() - ups1.mass() - mpi);
        _h[1]->fill(x);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2];
    const map<PdgId, unsigned int> mode = {{553, 1}, {211, 1}, {-211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1987_I238071);

}