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KLOE2_2017_I1634981

Cross section for $e^+e^-\to\pi^+\pi^-$ below 1 GeV
Experiment: KLOE2 (DAPHNE)
Inspire ID: 1634981
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • JHEP 1803 (2018) 173
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+\pi^-$ below 1 GeV

Source code: KLOE2_2017_I1634981.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4#include "Rivet/Projections/FastJets.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// @brief Add a short analysis description here
10  class KLOE2_2017_I1634981 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(KLOE2_2017_I1634981);
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    /// Perform the per-event analysis
30    void analyze(const Event& event) {
31      const FinalState& fs = apply<FinalState>(event, "FS");
32      if(fs.particles().size()!=2) vetoEvent;
33      for (const Particle& p : fs.particles()) {
34	if(abs(p.pid())!=PID::PIPLUS) vetoEvent;
35      }
36      _npion->fill();
37    }
38
39    /// Normalise histograms etc., after the run
40    void finalize() {
41      double sigma = _npion->val();
42      double error = _npion->err();
43      sigma *= crossSection()/ sumOfWeights() /nanobarn;
44      error *= crossSection()/ sumOfWeights() /nanobarn;
45      Scatter2D temphisto(refData(1, 1, 1));
46      Scatter2DPtr  mult;
47      book(mult, 1, 1, 1);
48      for (size_t b = 0; b < temphisto.numPoints(); b++) {
49	const double x  = temphisto.point(b).x();
50	pair<double,double> ex = temphisto.point(b).xErrs();
51	pair<double,double> ex2 = ex;
52	if(ex2.first ==0.) ex2. first=0.0001;
53	if(ex2.second==0.) ex2.second=0.0001;
54	if (inRange(sqr(sqrtS()/GeV), x-ex2.first, x+ex2.second)) {
55	  mult->addPoint(x, sigma, ex, make_pair(error,error));
56	}
57	else {
58	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
59	}
60      }
61    }
62
63    //@}
64
65
66    /// @name Histograms
67    //@{
68    CounterPtr _npion;
69    //@}
70
71
72  };
73
74
75  // The hook for the plugin system
76  RIVET_DECLARE_PLUGIN(KLOE2_2017_I1634981);
77
78
79}