Rivet analyses

title: BESIII_2013_I1261765

$\psi(2S)\to \Lambda^0\bar\Sigma^\pm\pi^\mp$ + c.c.

Experiment: BESIII (BEPC)

Inspire ID: 1261765

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 88 (2013) 11, 112007

Beams: * *

Beam energies: ANY

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

Measurements of mass distributions in the decays $\psi(2S)\to \Lambda^0\bar\Sigma^\pm\pi^\mp$ +c.c.. The data were read from the plots in the paper and may not be corrected for efficiency but the background given in the paper have been subtracted.

Source code:BESIII_2013_I1261765.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief psi(2S) -> Lambda Sigmabar+- pi-+ class BESIII_2013_I1261765 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2013_I1261765);


/// @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::SIGMAPLUS);
  psi.addStable(PID::SIGMAMINUS);
  psi.addStable(-PID::SIGMAPLUS);
  psi.addStable(-PID::SIGMAMINUS);
  psi.addStable(PID::LAMBDA);
  psi.addStable(-PID::LAMBDA);
  declare(psi, "psi");
  for (unsigned int ix = 0; ix < 3; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{3122, 1}, {-3222, 1}, {211, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{-3122, 1}, {3222, 1}, {-211, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{3122, 1}, {-3112, 1}, {-211, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{-3122, 1}, {3112, 1}, {211, 1}};
  DecayedParticles psi = apply<DecayedParticles>(event, "psi");
  for (unsigned int ix = 0; ix < psi.decaying().size(); ++ix) {
    int ipi = 211, isigma = -3222, sign = 1;
    if (psi.modeMatches(ix, 3, mode1)) {
      sign = 1;
    }
    else if (psi.modeMatches(ix, 3, mode1CC)) {
      sign = -1;
    }
    else if (psi.modeMatches(ix, 3, mode2)) {
      ipi = -211;
      isigma = -3112;
      sign = 1;
    }
    else if (psi.modeMatches(ix, 3, mode2CC)) {
      ipi = -211;
      isigma = -3112;
      sign = -1;
    }
    else
      continue;
    const Particle& lam = psi.decayProducts()[ix].at(sign * 3122)[0];
    const Particle& pim = psi.decayProducts()[ix].at(sign * ipi)[0];
    const Particle& sigma = psi.decayProducts()[ix].at(sign * isigma)[0];
    _h[0]->fill((lam.momentum() + pim.momentum()).mass());
    _h[1]->fill((pim.momentum() + sigma.momentum()).mass());
    _h[2]->fill((lam.momentum() + sigma.momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2013_I1261765);

} ```