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## Rivet analyses reference

### OPAL_1996_S3257789

$J/\psi$ and $\psi^\prime$ Production in Hadronic $Z^0$ Decays
Experiment: OPAL (LEP 1)
Inspire ID: 402487
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Z.Phys. C70 (1996) 197-210
Beams: e+ e-
Beam energies: (45.6, 45.6) GeV
Run details:
• Hadronic Z decay events generated on the Z pole ($\sqrt{s} = 91.2$ GeV)

The production of $J/\psi$ and $\psi^\prime$ mesons measured by the OPAL experiment at LEP. The fragmentation function for $J/\psi$ and the multiplicities of $J/\psi$ and $\psi^\prime$ are included.

Source code: OPAL_1996_S3257789.cc
  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 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/Beam.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/ChargedFinalState.hh" #include "Rivet/Projections/UnstableFinalState.hh" namespace Rivet { /// @brief OPAL J/Psi fragmentation function paper /// @author Peter Richardson class OPAL_1996_S3257789 : public Analysis { public: /// Constructor OPAL_1996_S3257789() : Analysis("OPAL_1996_S3257789"), _weightSum(0.) {} /// @name Analysis methods //@{ void init() { declare(Beam(), "Beams"); declare(ChargedFinalState(), "FS"); declare(UnstableFinalState(), "UFS"); _histXpJPsi = bookHisto1D( 1, 1, 1); _multJPsi = bookHisto1D( 2, 1, 1); _multPsiPrime = bookHisto1D( 2, 1, 2); } void analyze(const Event& e) { // First, veto on leptonic events by requiring at least 4 charged FS particles const FinalState& fs = apply(e, "FS"); const size_t numParticles = fs.particles().size(); // Even if we only generate hadronic events, we still need a cut on numCharged >= 2. if (numParticles < 2) { MSG_DEBUG("Failed leptonic event cut"); vetoEvent; } MSG_DEBUG("Passed leptonic event cut"); // Get event weight for histo filling const double weight = e.weight(); // Get beams and average beam momentum const ParticlePair& beams = apply(e, "Beams").beams(); const double meanBeamMom = ( beams.first.p3().mod() + beams.second.p3().mod() ) / 2.0; MSG_DEBUG("Avg beam momentum = " << meanBeamMom); // Final state of unstable particles to get particle spectra const UnstableFinalState& ufs = apply(e, "UFS"); foreach (const Particle& p, ufs.particles()) { if(p.abspid()==443) { double xp = p.p3().mod()/meanBeamMom; _histXpJPsi->fill(xp, weight); _multJPsi->fill(91.2,weight); _weightSum += weight; } else if(p.abspid()==100443) { _multPsiPrime->fill(91.2,weight); } } } /// Finalize void finalize() { if(_weightSum>0.) scale(_histXpJPsi , 0.1/_weightSum); scale(_multJPsi , 1./sumOfWeights()); scale(_multPsiPrime, 1./sumOfWeights()); } //@} private: double _weightSum; Histo1DPtr _histXpJPsi; Histo1DPtr _multJPsi; Histo1DPtr _multPsiPrime; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(OPAL_1996_S3257789); }