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BESII_2009_I814778

Measurement of $R$ for energies between 2.6 and 3.65 GeV
Experiment: BESII (BEPC)
Inspire ID: 814778
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B677 (2009) 239-245, 2009
Beams: e- e+
Beam energies: ANY
Run details:
  • e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of $R$ in $e^+e^-$ collisions by BESII for energies between 2.6 and 3.65 GeV. The individual hadronic and muonic cross sections are also outputted to the yoda file so that ratio $R$ can be recalculated if runs are combined.

Source code: BESII_2009_I814778.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 2.6 and 3.65 GeV
 9  class BESII_2009_I814778 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2009_I814778);
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      // Book histograms
24      book(_c_hadrons, "/TMP/sigma_hadrons");
25      book(_c_muons, "/TMP/sigma_muons");
26    }
27
28
29    /// Perform the per-event analysis
30    void analyze(const Event& event) {
31      const FinalState& fs = apply<FinalState>(event, "FS");
32
33      map<long,int> nCount;
34      int ntotal(0);
35      for (const Particle& p : fs.particles()) {
36        nCount[p.pid()] += 1;
37        ++ntotal;
38      }
39      // mu+mu- + photons
40      if(nCount[-13]==1 and nCount[13]==1 &&
41         ntotal==2+nCount[22])
42        _c_muons->fill();
43      // everything else
44      else
45        _c_hadrons->fill();
46    }
47
48
49    /// Normalise histograms etc., after the run
50    void finalize() {
51      Estimate0D R = *_c_hadrons/ *_c_muons;
52      double fact = crossSection()/ sumOfWeights() /nanobarn;
53      double sig_h = _c_hadrons->val()*fact;
54      double err_h = _c_hadrons->err()*fact;
55      double sig_m = _c_muons  ->val()*fact;
56      double err_m = _c_muons  ->err()*fact;
57      Estimate1DPtr hadrons;
58      book(hadrons, "sigma_hadrons");
59      Estimate1DPtr muons;
60      book(muons, "sigma_muons"  );
61      Estimate1DPtr mult;
62      book(mult, 1, 1, 1);
63      for (auto& b : mult->bins()) {
64        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
65          b.set(R.val(), R.errPos());
66          hadrons->bin(b.index()).set(sig_h, err_h);
67          muons  ->bin(b.index()).set(sig_m, err_m);
68        }
69      }
70    }
71
72    /// @}
73
74
75    /// @name Histograms
76    /// @{
77    CounterPtr _c_hadrons, _c_muons;
78    /// @}
79
80
81  };
82
83
84  RIVET_DECLARE_PLUGIN(BESII_2009_I814778);
85
86
87}