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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// -*- C++ -*-
 2#include "Rivet/Tools/AtlasCommon.hh"
 3#include "Rivet/Projections/ImpactParameterProjection.hh"
 4#include "Rivet/Analysis.hh"
 5
 6namespace Rivet {
 7
 8
 9class ATLAS_PBPB_CENTRALITY : public Analysis {
10
11public:
12
13  RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_PBPB_CENTRALITY);
14
15  /// Book histograms and initialise projections before the run
16  void init() {
17
18    // One projection for the actual observable, and one for the
19    // generated impact parameter.
20    declare(ATLAS::SumET_PBPB_Centrality(), "Centrality");
21    declare(ImpactParameterProjection(), "IMP");
22    declare(ATLAS::MinBiasTrigger(), "Trigger");
23
24    // The calibration histogram:
25    book(_calib, "sumETFwd");
26
27    // The alternative histogram based on impact parameter. Note that
28    // it MUST be named the same as the histogram for the experimental
29    // observable with an added _IMP suffix for the Pecentile<>
30    // binning to work properly.
31    book(_impcalib, "sumETFwd_IMP", 400, 0.0, 20.0);
32
33  }
34  
35  /// Perform the per-event analysis
36  void analyze(const Event& event) {
37
38    // The alternative centrality based on generated impact
39    // parameter, assumes that the generator does not describe the
40    // full final state, and should therefore be filled even if the
41    // event is not triggered.
42    _impcalib->fill(apply<SingleValueProjection>(event, "IMP")());
43
44    if ( !apply<ATLAS::MinBiasTrigger>(event, "Trigger")() ) vetoEvent;
45
46    _calib->fill(apply<ATLAS::SumET_PBPB_Centrality>(event, "Centrality")());
47
48  }
49  
50  /// Finalize
51  void finalize() {
52
53    _calib->normalize();
54    _impcalib->normalize();
55
56  }
57
58private:
59
60  /// The calibration histograms.
61  Histo1DPtr _calib;
62  Histo1DPtr _impcalib;
63
64};
65
66
67// The hook for the plugin system
68RIVET_DECLARE_PLUGIN(ATLAS_PBPB_CENTRALITY);
69
70}