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BESIII_2021_I1837968

Mass distributions in $\Lambda_c^+\to p K^0_S \eta$
Experiment: BESIII (BEPC)
Inspire ID: 1837968
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Lett.B 817 (2021) 136327
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing Lambda_c+ mesons

Measurement of the mass distributions in the decay $\Lambda_c^+\to p K^0_S \eta$ by BESIII. The data were read from the plots in the paper and may not have been corrected for efficiency/acceptance.

Source code: BESIII_2021_I1837968.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief Lambda_c+ -> p K0S eta
  class BESIII_2021_I1837968 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1837968);


    /// @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);
      declare(LAMBDAC, "LAMBDAC");
      // histograms
      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> & mode   = { { PID::PROTON,1}, {310,1}, { 221,1}};
      static const map<PdgId,unsigned int> & modeCC = { {-PID::PROTON,1}, {310,1}, { 221,1}};
      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 Particle & pp  = LAMBDAC.decayProducts()[ix].at( sign*PID::PROTON)[0];
	const Particle & eta = LAMBDAC.decayProducts()[ix].at( 221)[0];
	const Particle & K0  = LAMBDAC.decayProducts()[ix].at( 310)[0];
	_h[0]->fill((pp.momentum()+ K0.momentum()).mass());
	_h[1]->fill((K0.momentum()+eta.momentum()).mass());
	_h[2]->fill((pp.momentum()+eta.momentum()).mass());
      }
    }


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

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BESIII_2021_I1837968);

}