Rivet analyses referenceBESIII_2021_I1908066Cross section for $J/\psi$ production for energies between 3.645 and 3.8 GeVExperiment: BESIII (BEPC) Inspire ID: 1908066 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Cross section for the production of $J/\psi$ for energies between 3.645 and 3.8, i.e near the $\psi(2S)$ resonace measured by BESIII. Source code: BESIII_2021_I1908066.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief J/psi production at low energies
9 class BESIII_2021_I1908066 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2021_I1908066);
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(UnstableParticles(), "UFS");
24 book(_c_psi , "/TMP/sigma_psi");
25 }
26
27
28 /// Perform the per-event analysis
29 void analyze(const Event& event) {
30 const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
31 unsigned int count = ufs.particles(Cuts::pid==443).size();
32 _c_psi->fill(count);
33 }
34
35
36 /// Normalise histograms etc., after the run
37 void finalize() {
38 double fact = crossSection()/nanobarn/sumOfWeights();
39 double sigma = _c_psi->val()*fact;
40 double error = _c_psi->err()*fact;
41 Scatter2D temphisto(refData(1, 1, 1));
42 Scatter2DPtr mult;
43 book(mult, 1, 1, 1);
44 for (size_t b = 0; b < temphisto.numPoints(); b++) {
45 const double x = temphisto.point(b).x();
46 pair<double,double> ex = temphisto.point(b).xErrs();
47 pair<double,double> ex2 = ex;
48 if(ex2.first ==0.) ex2. first=0.0001;
49 if(ex2.second==0.) ex2.second=0.0001;
50 if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
51 mult ->addPoint(x, sigma, ex, make_pair(error,error));
52 }
53 else {
54 mult ->addPoint(x, 0., ex, make_pair(0.,.0));
55 }
56 }
57 }
58
59 ///@}
60
61
62 /// @name Histograms
63 ///@{
64 CounterPtr _c_psi;
65 ///@}
66
67
68 };
69
70
71 RIVET_DECLARE_PLUGIN(BESIII_2021_I1908066);
72
73}
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