Rivet analyses

Positron momentum spectrum in semileptonic Λc+ decay

Experiment: BESIII (BEPC)

Inspire ID: 2611489

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2212.03753

Beams: e+ e-

Beam energies: (2.0, 2.0); (3.0, 3.0)GeV

Run details: - e+e -> hadrons

Measurement of the positron momentum spectrum in the lab frame for semileptonic Λc+ decay.

Source code:BESIII_2022_I2611489.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Semileptonic Lambda_c+ 
  class BESIII_2022_I2611489 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2611489);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::abspid==4122),"UFS");
      // histos
      book(_h,1,1,1);
    }

    void findDecayProducts(Particle parent, Particles & em, Particles & ep,
               Particles & nue, Particles & nueBar) {
      for(const Particle & p : parent.children()) {
    if(p.pid() == PID::EMINUS) {
      em.push_back(p);
    }
    else if(p.pid() == PID::EPLUS) {
      ep.push_back(p);
    }
    else if(p.pid() == PID::NU_E) {
      nue.push_back(p);
    }
    else if(p.pid() == PID::NU_EBAR) {
      nueBar.push_back(p);
    }
    else if(!PID::isHadron(p.pid())) {
      findDecayProducts(p,em,ep,nue,nueBar);
    }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      for(const Particle & p : apply<UnstableParticles>(event, "UFS").particles()) {
    Particles em,ep,nue,nueBar;
    findDecayProducts(p,em,ep,nue,nueBar);
    if(em.size()==1 && nueBar.size()==1) {
      double pmod = em[0].momentum().p3().mod();
      _h->fill(pmod);
    }
    else if(ep.size()==1 && nue.size()==1) {
      double pmod = ep[0].momentum().p3().mod();
      _h->fill(pmod);
    }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h,1.,false);
    }

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BESIII_2022_I2611489);

}