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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: ANY
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, "/TMP/sigma_hadrons");
26      book(_c_muons,   "/TMP/sigma_muons");
27    }
28
29
30    /// Perform the per-event analysis
31    void analyze(const Event& event) {
32      const FinalState& fs = apply<FinalState>(event, "FS");
33
34      map<long,int> nCount;
35      int ntotal(0);
36      for (const Particle& p : fs.particles()) {
37        nCount[p.pid()] += 1;
38        ++ntotal;
39      }
40      // mu+mu- + photons
41      if(nCount[-13]==1 and nCount[13]==1 &&
42         ntotal==2+nCount[22])
43        _c_muons->fill();
44      // everything else
45      else
46        _c_hadrons->fill();
47    }
48
49
50    /// Normalise histograms etc., after the run
51    void finalize() {
52      Estimate0D R = *_c_hadrons/ *_c_muons;
53      double fact = crossSection()/ sumOfWeights() /nanobarn;
54      double sig_h = _c_hadrons->val()*fact;
55      double err_h = _c_hadrons->err()*fact;
56      double sig_m = _c_muons  ->val()*fact;
57      double err_m = _c_muons  ->err()*fact;
58      Estimate1DPtr hadrons;
59      book(hadrons, 2,1,1);
60      Estimate1DPtr muons;
61      book(muons, "sigma_muons"  );
62      Estimate1DPtr     mult;
63      book(mult, 2, 1, 2);
64      for (auto& b : mult->bins()) {
65        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
66          b.set(R.val(), R.errPos());
67          hadrons->bin(b.index()).set(sig_h, err_h);
68          muons->bin(b.index()).set(sig_m, err_m);
69        }
70      }
71    }
72
73    /// @}
74
75
76    /// @name Histograms
77    /// @{
78    CounterPtr _c_hadrons, _c_muons;
79    /// @}
80
81
82  };
83
84
85  RIVET_DECLARE_PLUGIN(BESII_2006_I717665);
86
87}