Rivet analyses

title: BESIII_2024_I2802565

$D_s^+\to K^0 e^+\nu_e$ $q^2$ spectrum

Experiment: BESIII (BEPC)

Inspire ID: 2802565

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 110 (2024) 5, 052012

Beams: * *

Beam energies: ANY

Run details: - Any process producing D_s+

Measurement of the $q^2$ spectrum in the decay $D_s^+\to K^0 e^+\nu_e$ by BES-III. The data are from Table 5 in the paper.

Source code:BESIII_2024_I2802565.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief q^2 in D_s+ -> K0 e+ nu_e class BESIII_2024_I2802565 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2802565);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 431);
  declare(ufs, "UFS");
  DecayedParticles DS(ufs);
  DS.addStable(PID::PI0);
  DS.addStable(PID::K0S);
  DS.addStable(PID::ETA);
  DS.addStable(PID::ETAPRIME);
  declare(DS, "DS");

  // Book histograms
  book(_h_q2, 1, 1, 1);
  book(_nD, "/TMP/nD");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{310, 1}, {-11, 1}, {12, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{130, 1}, {-11, 1}, {12, 1}};
  static const map<PdgId, unsigned int>& mode3 = {{311, 1}, {-11, 1}, {12, 1}};
  DecayedParticles DS = apply<DecayedParticles>(event, "DS");
  // loop over particles
  for (unsigned int ix = 0; ix < DS.decaying().size(); ++ix) {
    _nD->fill();
    if (DS.modeMatches(ix, 3, mode1)) {
      _h_q2->fill((DS.decaying()[ix].momentum() - DS.decayProducts()[ix].at(310)[0].momentum()).mass2());
    }
    else if (DS.modeMatches(ix, 3, mode2)) {
      _h_q2->fill((DS.decaying()[ix].momentum() - DS.decayProducts()[ix].at(130)[0].momentum()).mass2());
    }
    else if (DS.modeMatches(ix, 3, mode3)) {
      _h_q2->fill((DS.decaying()[ix].momentum() - DS.decayProducts()[ix].at(311)[0].momentum()).mass2());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // normalise to width in inverse ns
  scale(_h_q2, 1. / 0.504e-3 / *_nD);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_q2;
CounterPtr _nD;
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2024_I2802565);

} ```