Rivet analyses

title: BESIII_2019_I1711896

Mass distributions in $\Lambda_c^+\to\Lambda^0\eta\pi^+$

Experiment: BESIII (BEPC)

Inspire ID: 1711896

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 3, 032010

Beams: * *

Beam energies: ANY

Run details: - Any process producing Lambda_c+ mesons

Measurement of the mass distributions in the decay $\Lambda_c^+\to\Lambda^0\eta\pi^+$ byt BESIII. The data were read from the plots in the paper, it is not clear that any resolution/efficiency effects have been unfolded.

Source code:BESIII_2019_I1711896.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda_c+ -> Lambda eta pi+ class BESIII_2019_I1711896 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1711896);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 4122);
  declare(ufs, "UFS");
  DecayedParticles LAMBDAC(ufs);
  LAMBDAC.addStable(PID::PI0);
  LAMBDAC.addStable(PID::K0S);
  LAMBDAC.addStable(PID::ETA);
  LAMBDAC.addStable(PID::ETAPRIME);
  LAMBDAC.addStable(PID::LAMBDA);
  declare(LAMBDAC, "LAMBDAC");
  // histograms
  book(_h, 1, 1, 1);
  book(_dalitz, "dalitz", 50, 1.5, 3.5, 50, 2.5, 5.0);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{211, 1}, {221, 1}, {PID::LAMBDA, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-211, 1}, {221, 1}, {-PID::LAMBDA, 1}};
  DecayedParticles LAMBDAC = apply<DecayedParticles>(event, "LAMBDAC");
  // loop over particles
  for (unsigned int ix = 0; ix < LAMBDAC.decaying().size(); ++ix) {
    int sign = 1;
    if (LAMBDAC.decaying()[ix].pid() > 0 && LAMBDAC.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (LAMBDAC.decaying()[ix].pid() < 0 && LAMBDAC.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particles& lam = LAMBDAC.decayProducts()[ix].at(sign * PID::LAMBDA);
    const Particles& pip = LAMBDAC.decayProducts()[ix].at(sign * PID::PIPLUS);
    const Particles& eta = LAMBDAC.decayProducts()[ix].at(PID::ETA);
    double mLamPi = (lam[0].momentum() + pip[0].momentum()).mass2();
    double mLamEta = (lam[0].momentum() + eta[0].momentum()).mass2();
    _dalitz->fill(mLamPi, mLamEta);
    _h->fill(sqrt(mLamPi));
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2019_I1711896);

} ```