Rivet analyses referenceSND_2020_I1789269Cross section for $e^+e^-\to \pi^+\pi^-$ at energies between 0.525 and 0.883 GeVExperiment: SND (VEPP-2M) Inspire ID: 1789269 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the cross section for $e^+e^-\to \pi^+\pi^-$ at energies between 0.525 and 0.883 GeV Source code: SND_2020_I1789269.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4
5namespace Rivet {
6
7
8 /// @brief e+e- -> pi+pi-
9 class SND_2020_I1789269 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1789269);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
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 Estimate1DPtr mult;
48 book(mult, 1, 1, 4);
49 for (auto& b : mult->bins()) {
50 if (inRange(sqrtS()/MeV, b.xMin(), b.xMax())) {
51 b.set(sigma, error);
52 }
53 }
54 }
55
56 /// @}
57
58
59 /// @name Histograms
60 /// @{
61 CounterPtr _npion;
62 /// @}
63
64
65 };
66
67
68 RIVET_DECLARE_PLUGIN(SND_2020_I1789269);
69
70}
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