Rivet analyses

title: MC_CENT_PPB_CALIB

Template analysis for generating calibration histograms for centrality

Experiment: ()

Status: UNVALIDATED

Authors: - Leif Lönnblad

References: - arXiv: 1508.00848 - Eur.Phys.J. C76 (2016) no.4, 199

Beams: * *

Beam energies: ANY

Run details: - Any!

Template analysis for generating calibration histograms to be used together with the CentralityProjection and Percentile<> classes. The example is pPb collisions at 5 TeV and is based on the ATLAS analysis arXiv:1508.00848 [hep-ex]. The reference YODA file contains the experimental centrality calibration, but extracted from the plot in the paper. Note that this has not been unfolded for detector effects.

Source code:MC_CENT_PPB_CALIB.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Analyses/MC_CENT_PPB_Projections.hh"

include "Rivet/Projections/ImpactParameterProjection.hh"

namespace Rivet {

/// Generic analysis looking at various distributions of final state particles class MC_CENT_PPB_CALIB : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(MC_CENT_PPB_CALIB);


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

  // One projection for the actual observable, and one for the
  // generated impact parameter.
  declare(MC_SumETFwdPbCentrality(), "Centrality");
  declare(ImpactParameterProjection(), "IMP");
  declare(MC_pPbMinBiasTrigger(), "Trigger");

  // The calibrationhistogram:
  book(_calib, "SumETPb", 100, 0.0, 200.0);

  // If histogram was pre-loaded, the calibration is done.
  _done = (_calib->numEntries() > 0);

  // The alternative histogram based on impact parameter. Note that
  // it MUST be named the same as the histogram for the experimental
  // observable with an added _IMP suffix for the Pecentile<>
  // binning to work properly.
  book(_impcalib, "SumETPb_IMP", 400, 0.0, 20.0);
}

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

  if (_done) return;

  // The alternative centrality based on generated impact
  // parameter, assumes that the generator does not describe the
  // full final state, and should therefore be filled even if the
  // event is not triggered.
  _impcalib->fill(apply<SingleValueProjection>(event, "IMP")());

  if (!apply<TriggerProjection>(event, "Trigger")()) vetoEvent;

  _calib->fill(apply<SingleValueProjection>(event, "Centrality")());
}

/// Finalize
void finalize() {

  _calib->normalize();
  _impcalib->normalize();
}

private:

/// The calibration histograms.
Histo1DPtr _calib;
Histo1DPtr _impcalib;

/// Safeguard from adding to a pre-loaded histogram.
bool _done;

};

RIVET_DECLARE_PLUGIN(MC_CENT_PPB_CALIB);

} ```