Rivet analyses

title: CMD2_2008_I782516

Cross section for $e^+e^-\to K^+K^-$ near the $\phi$ mass

Experiment: CMD2 (VEPP-2M)

Inspire ID: 782516

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B669 (2008) 217-222, 2008

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to K^+K^-$ at near the $\phi$ mass.

Source code:CMD2_2008_I782516.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Add a short analysis description here class CMD2_2008_I782516 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_2008_I782516);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");

  // Book histograms
  book(_nkaon, "TMP/kaon");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  if (fs.particles().size() != 2) vetoEvent;
  for (const Particle& p : fs.particles()) {
    if (abs(p.pid()) != PID::KPLUS) vetoEvent;
  }
  _nkaon->fill();
}


/// Normalise histograms etc., after the run
void finalize() {
  double sigma = _nkaon->val();
  double error = _nkaon->err();
  sigma *= crossSection() / sumOfWeights() / nanobarn;
  error *= crossSection() / sumOfWeights() / nanobarn;
  for (unsigned int ix = 1; ix < 3; ++ix) {
    Estimate1DPtr mult;
    book(mult, ix, 1, 1);
    for (auto& b : mult->bins()) {
      if (inRange(sqrtS() / MeV, b.xMin(), b.xMax())) {
        b.set(sigma, error);
      }
    }
  }
}

/// @}


/// @name Histograms
/// @{
CounterPtr _nkaon;
/// @}

};

RIVET_DECLARE_PLUGIN(CMD2_2008_I782516);

} ```