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 CMD3_2023_I2634277 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(CMD3_2023_I2634277);
14
15
16    /// @name Analysis methods
17    /// @{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      // Initialise and register projections
22      declare(FinalState(), "FS");
23
24      // Book histograms
25      for (unsigned int ix=0; ix<3; ++ix) {
26        book(_sigma[ix], 1, 1+ix, 1);
27        for (const string& en : _sigma[ix].binning().edges<0>()) {
28          const double end = std::stod(en)*MeV;
29          if (isCompatibleWithSqrtS(end)) {
30            _ecms[ix] = en;
31            break;
32          }
33        }
34      }
35      if (_ecms[0].empty() && _ecms[1].empty() && _ecms[2].empty()) {
36        MSG_ERROR("Beam energy incompatible with analysis.");
37      }
38    }
39
40
41    /// Perform the per-event analysis
42    void analyze(const Event& event) {
43      const FinalState& fs = apply<FinalState>(event, "FS");
44      if(fs.particles().size()!=2) vetoEvent;
45      for (const Particle& p : fs.particles()) {
46        if (abs(p.pid())!=PID::PIPLUS) vetoEvent;
47      }
48      for(unsigned int ix=0;ix<3;++ix) {
49        if(!_ecms[ix].empty()) _sigma[ix]->fill(_ecms[ix]);
50      }
51    }
52
53
54    /// Normalise histograms etc., after the run
55    void finalize() {
56      const double gev2nb =0.389e6;
57      const double beta = sqrt(1.-4.*sqr(0.13957039/sqrtS()));
58      const double alpha = 1./137.035999084;
59      const double sigma0 = gev2nb*M_PI*sqr(alpha)*beta*sqr(beta)/3/sqr(sqrtS());
60      for(unsigned int ix=0;ix<3;++ix)
61        scale(_sigma[ix], crossSection()/ sumOfWeights() /nanobarn /sigma0);
62    }
63
64    /// @}
65
66
67    /// @name Histograms
68    /// @{
69    BinnedHistoPtr<string> _sigma[3];
70    string _ecms[3];
71    /// @}
72
73
74  };
75
76
77  RIVET_DECLARE_PLUGIN(CMD3_2023_I2634277);
78
79}