Rivet analyses

title: BESIII_2022_I2513076

$\pi^0$ and $K^0_S$ momentum distributions for energies between 2.23 and 3.67 GeV

Experiment: BESIII (BEPC)

Inspire ID: 2513076

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 1605.2211.11253

Beams: e+ e-

Beam energies: (1.1, 1.1); (1.2, 1.2); (1.4, 1.4); (1.5, 1.5); (1.7, 1.7); (1.8, 1.8)GeV

Run details: - e+e- to hadrons.

$\pi^0$ and $K^0_S$ momentum distributions for energies between 2.23 and 3.67 GeV.

Source code:BESIII_2022_I2513076.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief pi0/K0 spectra class BESIII_2022_I2513076 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2513076);


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

/// Book histograms and initialise projections before the run
void init() {
  // projection
  declare(UnstableParticles(Cuts::pid == PID::PI0 || Cuts::pid == PID::K0S), "UFS");
  // find beam energy
  size_t ih = 1;
  for (double eVal : allowedEnergies()) {

    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;

    book(_h[en + "_1"], 1, 1, ih);
    book(_h[en + "_2"], 2, 1, ih);
    book(_c[en], "_aux_sigma_" + en);
    ++ih;
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  _c[_sqs]->fill();
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    const double pp = p.p3().mod();
    if (p.pid() == PID::PI0)
      _h[_sqs + "_1"]->fill(pp);
    else
      _h[_sqs + "_2"]->fill(pp);
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h, crossSectionPerEvent());
  scale(_c, crossSectionPerEvent());
  for (const auto& item : _c) {
    scale(_h[item.first + "_1"s], 1.0 / item.second->sumW());
    scale(_h[item.first + "_2"s], 1.0 / item.second->sumW());
  }
}

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
map<string, CounterPtr> _c;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2022_I2513076);

} ```