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## Rivet analyses reference

### ATLAS_PBPB_CENTRALITY

Centrality calibration / forward energy flow Pb--Pb.
Experiment: ()
Status: UNVALIDATED
Authors:
• Christian Bierlich
References:
• arXiv: 1108.6018
• Phys.Lett. B707 (2012) 330-348
Beams: * *
Beam energies: ANY
Run details:
• Any!

Calibration analysis for ATLAS Pb--Pb centrality. The centrality measure is $\sum E_\perp$ in the forward and backward directions. The reference YODA file contains the experimental centrality calibration, but extracted from the plot in the paper. Analysis can be run for all energies to provide generator calibration curves, but only holds data for 2.76 TeV/nn. Note that this has not been unfolded for detector effects.

Source code: ATLAS_PBPB_CENTRALITY.cc
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 // -*- C++ -*- #include "Rivet/Tools/AtlasCommon.hh" #include "Rivet/Projections/ImpactParameterProjection.hh" #include "Rivet/Analysis.hh" namespace Rivet { class ATLAS_PBPB_CENTRALITY : public Analysis { public: DEFAULT_RIVET_ANALYSIS_CTOR(ATLAS_PBPB_CENTRALITY); /// Book histograms and initialise projections before the run void init() { // One projection for the actual observable, and one for the // generated impact parameter. declare(ATLAS::SumET_PBPB_Centrality(), "Centrality"); declare(ImpactParameterProjection(), "IMP"); declare(ATLAS::MinBiasTrigger(), "Trigger"); // The calibration histogram: book(_calib, "sumETFwd"); // 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, "sumETFwd_IMP", 400, 0.0, 20.0); } /// Perform the per-event analysis void analyze(const Event& event) { // 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(event, "IMP")()); if ( !apply(event, "Trigger")() ) vetoEvent; _calib->fill(apply(event, "Centrality")()); } /// Finalize void finalize() { _calib->normalize(); _impcalib->normalize(); } private: /// The calibration histograms. Histo1DPtr _calib; Histo1DPtr _impcalib; }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(ATLAS_PBPB_CENTRALITY); }