Rivet analyses

title: BELLE_2013_I1245023

$\gamma\gamma\to K^0_SK^0_S$ for centre-of-mass energies between 1.05 and 4.0 GeV

Experiment: BELLE (KEKB)

Inspire ID: 1245023

Status: VALIDATED

Authors: - Peter Richardson

References: - PTEP 2013 (2013) 12, 123C01

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma to hadrons, K0S meson must be set stable

Measurement of the differential cross section for $\gamma\gamma\to K^0_SK^0_S$ for $1.05 \text{GeV} < W < 4.0 \text{GeV}$. Both the cross section as a function of the centre-of-mass energy of the photonic collision, and the differential cross section with respect to the kaon scattering angle are measured.

Source code:BELLE_2013_I1245023.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief gamma gamma -> K0S K0S class BELLE_2013_I1245023 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1245023);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  // histos
  if (inRange(sqrtS() / GeV, 1.05, 4.0)) {
    if (sqrtS() > 1.1) book(_sigmaKK[0], "TMP/nKK_1", refData(1, 1, 1));
    book(_sigmaKK[1], "TMP/nKK_2", refData(1, 1, 2));
    double sMin = 1.1, step = 0.01;
    unsigned int ihist = 2, iy = 1;
    while (sMin < 3.3) {
      if (inRange(sqrtS() / GeV, sMin, sMin + step)) {
        break;
      }
      sMin += step;
      iy += 1;
      if (iy == 4) {
        ihist += 1;
        iy = 1;
      }
      if (fuzzyEquals(1.9, sMin))
        step = 0.02;
      else if (fuzzyEquals(2.4, sMin))
        step = 0.04;
      else if (fuzzyEquals(2.6, sMin))
        step = 0.1;
    }
    if (ihist <= 40) book(_h_cTheta, ihist, 1, iy);
  }
  else {
    throw Error("Invalid CMS energy for BELLE_2013_I1245023");
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  Particles part = apply<FinalState>(event, "FS").particles();
  if (part.size() != 2) vetoEvent;
  for (const Particle& p : part) {
    if (p.pid() != PID::K0S) vetoEvent;
  }
  const double cTheta = abs(part[0].momentum().z() / part[0].momentum().p3().mod());
  if (cTheta <= 0.6) _sigmaKK[1]->fill(sqrtS());
  if (cTheta <= 0.8 && _sigmaKK[0]) _sigmaKK[0]->fill(sqrtS());
  if (_h_cTheta) _h_cTheta->fill(cTheta);
}


/// Normalise histograms etc., after the run
void finalize() {
  const double fact = crossSection() / nanobarn / sumOfWeights();
  if (_h_cTheta) scale(_h_cTheta, fact);
  for (unsigned int ix = 0; ix < 2; ++ix) {
    if (!_sigmaKK[ix]) continue;
    scale(_sigmaKK[ix], fact);
    Estimate1DPtr tmp;
    book(tmp, 1, 1, 1 + ix);
    barchart(_sigmaKK[ix], tmp);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _sigmaKK[2], _h_cTheta;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2013_I1245023);

} ```