Rivet analyses

MC analysis for process total cross section

Experiment: ()

Status: VALIDATED

Authors: - Marek Schoenherr - Christian Gutschow

References: none listed

Beams: * *

Beam energies: ANY

Run details: - Suitable for any process.

Analysis for bookkeeping of the total cross section, number of generated events and the ratio of events with positive and negative weights. This analysis will not produce sensible distributions in case of correlated NLO sub-events.

Source code:MC_XS.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/AnalysisHandler.hh"

namespace Rivet {


  /// Analysis of the generated cross-section
  class MC_XS : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(MC_XS);


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

    /// Book histograms and initialise projections before the run
    void init() {
      /// @todo Convert to Scatter1D or Counter
      book(_h_XS, "XS");
      book(_h_N, "N", 1, 0.0, 1.0);
      book(_h_pmXS, "pmXS", 2, -1.0, 1.0);
      book(_h_pmN, "pmN", 2, -1.0, 1.0);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      const size_t numWeights = event.weights().size();
      const vector<pair<double,double>> xsecs = event.crossSections();
      for (size_t m = 0; m < numWeights; ++m) {
        size_t idx = (xsecs.size() == numWeights)? m : 0;
        const double xs    = xsecs[idx].first;
        const double xserr = xsecs[idx].second;
        _h_XS.get()->persistent(m)->set(xs, xserr);
        const double weight = event.weights()[m];
        _h_pmXS.get()->persistent(m)->fill(0.5*(weight > 0 ? 1. : -1), abs(weight));
        _h_pmN.get()->persistent(m)->fill(0.5*(weight > 0 ? 1. : -1), 1.);
        _h_N.get()->persistent(m)->fill(0.5, 1.0);
      }

    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_pmXS, crossSection()/picobarn/sumOfWeights());
    }

    /// @}


    /// @name Histograms
    /// @{
    Estimate0DPtr _h_XS;
    Histo1DPtr _h_pmXS, _h_pmN, _h_N;
    /// @}

  };



  RIVET_DECLARE_PLUGIN(MC_XS);

}