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