Rivet analyses

title: BESIII_2013_I1120737

$\psi(2S)\to p \bar{p}\pi^0$

Experiment: BESIII (BEPC)

Inspire ID: 1120737

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 110 (2013) 2, 022001

Beams: * *

Beam energies: ANY

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

Measurement of the mass distributions in the decay $\psi(2S)\to p \bar{p}\pi^0$. The data were read from the plots in the paper. It is also not clear that any resolution effects have been unfolded.

Source code:BESIII_2013_I1120737.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> p pbar pi0 class BESIII_2013_I1120737 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1120737);


/// @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");
  book(_h_ppi0, 1, 1, 1);
  book(_dalitz, "dalitz", 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}, {-2212, 1}, {111, 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)) continue;
    const Particles& pi0 = psi.decayProducts()[ix].at(111);
    const Particles& pp = psi.decayProducts()[ix].at(2212);
    const Particles& pbar = psi.decayProducts()[ix].at(-2212);
    double mminus = (pbar[0].momentum() + pi0[0].momentum()).mass2();
    double mplus = (pp[0].momentum() + pi0[0].momentum()).mass2();
    _h_ppi0->fill(sqrt(mplus));
    _dalitz->fill(mplus, mminus);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_dalitz);
  normalize(_h_ppi0);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_ppi0;
Histo2DPtr _dalitz;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2013_I1120737);

} ```