Rivet analyses

title: BES_2005_I689969

Mass distributions in $\psi(2S)\to\pi^+\pi^-\pi^0$

Experiment: BES (BEPC)

Inspire ID: 689969

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 619 (2005) 247-254

Beams: * *

Beam energies: ANY

Run details: - Any process producingpsi(2S), originally e+e-

Measurement of the $\pi\pi$ mass distribution in the decays $\psi(2S)\to\pi^+\pi^-\pi^0$ be BES. N.B. data read from plots and may not be corrected.

Source code:BES_2005_I689969.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> pi+pi-pi0 class BES_2005_I689969 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BES_2005_I689969);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 100443);
  declare(ufs, "UFS");
  DecayedParticles psi2S(ufs);
  psi2S.addStable(PID::PI0);
  psi2S.addStable(PID::K0S);
  psi2S.addStable(PID::ETA);
  psi2S.addStable(PID::ETAPRIME);
  declare(psi2S, "psi2S");
  book(_h_pipi, 1, 1, 1);
  book(_dalitz, "dalitz", 50, 0., 14., 50, 0.0, 14.);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {111, 1}};
  DecayedParticles psi2S = apply<DecayedParticles>(event, "psi2S");
  // loop over particles
  for (unsigned int ix = 0; ix < psi2S.decaying().size(); ++ix) {
    if (!psi2S.modeMatches(ix, 3, mode)) continue;
    const Particles& pi0 = psi2S.decayProducts()[ix].at(111);
    const Particles& pip = psi2S.decayProducts()[ix].at(211);
    const Particles& pim = psi2S.decayProducts()[ix].at(-211);
    double mminus = (pim[0].momentum() + pi0[0].momentum()).mass2();
    double mplus = (pip[0].momentum() + pi0[0].momentum()).mass2();
    double mneut = (pip[0].momentum() + pim[0].momentum()).mass2();
    _h_pipi->fill(sqrt(mneut));
    _h_pipi->fill(sqrt(mplus));
    _h_pipi->fill(sqrt(mminus));
    _dalitz->fill(mplus, mminus);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_pipi);
  normalize(_dalitz);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pipi;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BES_2005_I689969);

} ```