Rivet analyses referenceSND_2024_I2696331Cross section for $e^+e^-\to n\bar{n}$ for $\sqrt{s}$ between 1.891 and 2.007 GeVExperiment: SND (VEPP-2000) Inspire ID: 2696331 Status: VALIDATED NOHEPDATA Authors:
Beam energies: (0.9, 0.9); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0); (1.0, 1.0) GeV Run details:
Measurement of the cross section for $e^+e^-\to n\bar{n}$ for $\sqrt{s}$ between 1.891 and 2.007 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples. Source code: SND_2024_I2696331.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/FastJets.hh"
5#include "Rivet/Projections/LeptonFinder.hh"
6#include "Rivet/Projections/MissingMomentum.hh"
7#include "Rivet/Projections/DirectFinalState.hh"
8
9namespace Rivet {
10
11
12 /// @brief e+ e- > n nbar
13 class SND_2024_I2696331 : public Analysis {
14 public:
15
16 /// Constructor
17 RIVET_DEFAULT_ANALYSIS_CTOR(SND_2024_I2696331);
18
19
20 /// @name Analysis methods
21 /// @{
22
23 /// Book histograms and initialise projections before the run
24 void init() {
25 // Initialise and register projections
26 declare(FinalState(), "FS");
27
28 // Book histograms
29 book(_nneutron, 1, 1, 1);
30
31 for (const string& en : _nneutron.binning().edges<0>()) {
32 double end = 2.*std::stod(en)*MeV;
33 if(isCompatibleWithSqrtS(end)) {
34 _ecms = en;
35 break;
36 }
37 }
38 if(_ecms.empty()) MSG_ERROR("Beam energy incompatible with analysis.");
39 }
40
41
42 /// Perform the per-event analysis
43 void analyze(const Event& event) {
44 const FinalState& fs = apply<FinalState>(event, "FS");
45 if (fs.particles().size()!=2) vetoEvent;
46 for (const Particle& p : fs.particles()) {
47 if(abs(p.pid())!=PID::NEUTRON) vetoEvent;
48 }
49 _nneutron->fill(_ecms);
50 }
51
52
53 /// Normalise histograms etc., after the run
54 void finalize() {
55 scale(_nneutron, crossSection()/ sumOfWeights() /nanobarn);
56 }
57
58 /// @}
59
60
61 /// @name Histograms
62 /// @{
63 BinnedHistoPtr<string> _nneutron;
64 string _ecms;
65 /// @}
66
67
68 };
69
70
71 RIVET_DECLARE_PLUGIN(SND_2024_I2696331);
72
73}
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