Rivet analyses

γγ → KS0KS0 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 γγ → KS0KS0 for 1.05GeV < W < 4.0GeV. 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++ -*-
#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);

}