rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

CELLO_1989_I276764

Photon, $\pi^0$ and $\eta$ spectra at 35 GeV
Experiment: CELLO (Petra)
Inspire ID: 276764
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Z.Phys. C47 (1990) 1-10, 1990
Beams: e+ e-
Beam energies: (17.5, 17.5) GeV
Run details:
  • e+ e- to hadrons

Measurement of the $\gamma$, $\pi^0$ and $\eta$ energy fractions in $e^+e^-$ collisions for centre-of-mass energy of 35 GeV by the CELLO experiment at Petra. Only the bin centroids are given in the paper and HEPdata so the bin widths have been inferred.

Source code: CELLO_1989_I276764.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4#include "Rivet/Projections/UnstableParticles.hh"
 5#include "Rivet/Projections/Beam.hh"
 6
 7namespace Rivet {
 8
 9
10  /// @brief Add a short analysis description here
11  class CELLO_1989_I276764 : public Analysis {
12  public:
13
14    /// Constructor
15    RIVET_DEFAULT_ANALYSIS_CTOR(CELLO_1989_I276764);
16
17
18    /// @name Analysis methods
19    //@{
20
21    /// Book histograms and initialise projections before the run
22    void init() {
23
24      // Initialise and register projections
25      declare(Beam(), "Beams");
26      declare(FinalState(), "FS");
27      declare(UnstableParticles(), "UFS");
28      // Book histograms
29      book(_h_gamma , 2, 1, 1);
30      book(_h_pi0A  , 3, 1, 1);
31      book(_h_pi0B  , 4, 1, 1);
32      book(_h_eta   , 5, 1, 1);
33    }
34
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      // at least 5 charged FS particles
39      const FinalState& fs = apply<FinalState>(event, "FS");
40      const size_t numParticles = fs.particles().size();
41
42      if (numParticles < 5) {
43        MSG_DEBUG("Failed leptonic event cut");
44        vetoEvent;
45      }
46      MSG_DEBUG("Passed leptonic event cut");
47
48      // Get beams and average beam momentum
49      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
50      const double meanBeamMom = ( beams.first.p3().mod() +
51                                   beams.second.p3().mod() ) / 2.0;
52      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
53
54      // Final state to get particle spectra
55      for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==111 || Cuts::pid==221)) {
56	double xE = p.E()/meanBeamMom;
57	if(p.pid()==111) {
58	  _h_pi0A->fill(xE);
59	  _h_pi0B->fill(xE);
60	}
61	else
62	  _h_eta->fill(xE);
63      }
64      for (const Particle& p : apply<FinalState>(event, "FS").particles(Cuts::pid==111 || Cuts::pid==22)) {
65	double xE = p.E()/meanBeamMom;
66	if(p.pid()==22)
67	  _h_gamma->fill(xE);
68      }
69    }
70
71
72    /// Normalise histograms etc., after the run
73    void finalize() {
74
75      double fact = sqr(sqrtS())/GeV2*crossSection()/microbarn/sumOfWeights();
76      scale(_h_gamma, fact); 
77      scale(_h_pi0A , fact); 
78      scale(_h_pi0B , fact); 
79      scale(_h_eta  , fact); 
80
81    }
82
83    //@}
84
85
86    /// @name Histograms
87    //@{
88    Histo1DPtr _h_gamma,_h_pi0A,_h_pi0B,_h_eta;
89
90
91  };
92
93
94  // The hook for the plugin system
95  RIVET_DECLARE_PLUGIN(CELLO_1989_I276764);
96
97
98}