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);

}