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BESII_2006_I717665

Measurement of $R$ for energies between 3.65 and 3.773 GeV
Experiment: BESII (BEPC)
Inspire ID: 717665
Status: VALIDATED SINGLEWEIGHT
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B641 (2006) 145-155, 2006
Beams: e- e+
Beam energies: (1.8, 1.8); (1.8, 1.8); (1.9, 1.9) GeV
Run details:
  • e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of $R$ and the hadronic cross section in $e^+e^-$ collisions by BESII for energies between 3.65 and 3.773, in the vicinity of the $\psi(3770)$. The muonic cross section is also outputted to the yoda file so that ratio $R$ can be recalculated if runs are combined.

Source code: BESII_2006_I717665.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Measurement of R for energies between 3.65 and 3.773 GeV
 9  class BESII_2006_I717665 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2006_I717665);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Initialise and register projections
22      declare(FinalState(), "FS");
23
24      // Book histograms
25      book(_c_hadrons, 2,1,1);
26      book(_c_muons,   "/TMP/sigma_muons", refData<YODA::BinnedEstimate<string>>(2,1,1));
27      for (const string& en : _c_hadrons.binning().edges<0>()) {
28        double end = std::stod(en)*GeV;
29        if(isCompatibleWithSqrtS(end)) {
30          _ecms = en;
31          break;
32        }
33      }
34      if(_ecms.empty())
35        MSG_ERROR("Beam energy incompatible with analysis.");
36    }
37
38
39    /// Perform the per-event analysis
40    void analyze(const Event& event) {
41      const FinalState& fs = apply<FinalState>(event, "FS");
42
43      map<long,int> nCount;
44      int ntotal(0);
45      for (const Particle& p : fs.particles()) {
46        nCount[p.pid()] += 1;
47        ++ntotal;
48      }
49      // mu+mu- + photons
50      if(nCount[-13]==1 and nCount[13]==1 &&
51         ntotal==2+nCount[22])
52        _c_muons->fill(_ecms);
53      // everything else
54      else
55        _c_hadrons->fill(_ecms);
56    }
57
58
59    /// Normalise histograms etc., after the run
60    void finalize() {
61      BinnedEstimatePtr<string> mult;
62      book(mult,2,1,2);
63      divide(_c_hadrons, _c_muons, mult);
64      scale(_c_hadrons,crossSection()/ sumOfWeights() /nanobarn);
65    }
66
67    /// @}
68
69
70    /// @name Histograms
71    /// @{
72    BinnedHistoPtr<string> _c_hadrons, _c_muons;
73    string _ecms;
74    /// @}
75
76
77  };
78
79
80  RIVET_DECLARE_PLUGIN(BESII_2006_I717665);
81
82}