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Rivet analyses reference

CMD2_1999_I498859

Cross section for $e^+e^-\to \pi^+\pi^-$ at near the $\rho$ mass.
Experiment: CMD2 (VEPP-2M)
Inspire ID: 498859
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B527 (2002) 161-172, 2002
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Source code: CMD2_1999_I498859.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5
 6namespace Rivet {
 7
 8
 9  /// @brief Add a short analysis description here
10  class CMD2_1999_I498859 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(CMD2_1999_I498859);
15
16
17    /// @name Analysis methods
18    //@{
19
20    /// Book histograms and initialise projections before the run
21    void init() {
22      // Initialise and register projections
23      declare(FinalState(), "FS");
24
25      // Book histograms
26      book(_npion, "TMP/pion");
27    }
28
29
30    /// Perform the per-event analysis
31    void analyze(const Event& event) {
32      const FinalState& fs = apply<FinalState>(event, "FS");
33      if(fs.particles().size()!=2) vetoEvent;
34      for (const Particle& p : fs.particles()) {
35	if(abs(p.pid())!=PID::PIPLUS) vetoEvent;
36      }
37      _npion->fill();
38    }
39
40
41    /// Normalise histograms etc., after the run
42    void finalize() {
43      double sigma = _npion->val();
44      double error = _npion->err();
45      sigma *= crossSection()/ sumOfWeights() /nanobarn;
46      error *= crossSection()/ sumOfWeights() /nanobarn;
47      Scatter2D temphisto(refData(1, 1, 1));
48      Scatter2DPtr mult;
49      book(mult, 1, 1, 1);
50      for (size_t b = 0; b < temphisto.numPoints(); b++) {
51	const double x  = temphisto.point(b).x();
52	pair<double,double> ex = temphisto.point(b).xErrs();
53	pair<double,double> ex2 = ex;
54	if(ex2.first ==0.) ex2. first=0.0001;
55	if(ex2.second==0.) ex2.second=0.0001;
56	if (inRange(sqrtS()/MeV, x-ex2.first, x+ex2.second)) {
57	  mult->addPoint(x, sigma, ex, make_pair(error,error));
58	}
59	else {
60	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
61	}
62      }
63    }
64
65    //@}
66
67
68    /// @name Histograms
69    //@{
70    CounterPtr _npion;
71    //@}
72
73
74  };
75
76
77  // The hook for the plugin system
78  RIVET_DECLARE_PLUGIN(CMD2_1999_I498859);
79
80
81}