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## Rivet analyses reference

### HRS_1988_I250824

$\eta$ spectrum in $e^+e^-$ collisions at 29 GeV
Experiment: HRS (PEP)
Inspire ID: 250824
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Lett. B205 (1988) 111-114
Beams: e+ e-
Beam energies: (14.5, 14.5) GeV
Run details:
• Hadronic e+e- events at $\sqrt{s} = 29.$ GeV

$\eta$ meson momentum spectrum measured at $\sqrt{s} = 29.$ GeV using the HRS detector at PEP. The bin widths are not included in either the paper or HEPdata and have therefore been infered.

Source code: HRS_1988_I250824.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 // -*- 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 HRS_1988_I250824 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(HRS_1988_I250824); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { declare(Beam(), "Beams"); declare(FinalState(), "FS"); declare(UnstableParticles(), "UFS"); // Book histograms book(_h_eta, 1 , 1, 1); } /// Perform the per-event analysis void analyze(const Event& event) { // First, veto on leptonic events by requiring at least 4 charged FS particles const FinalState& fs = apply(event, "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 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==221)) { double xE = p.E()/meanBeamMom; _h_eta->fill(xE); } } /// Normalise histograms etc., after the run void finalize() { double fact = sqr(sqrtS())/GeV2*crossSection()/microbarn/sumOfWeights(); scale(_h_eta, fact); } //@} /// @name Histograms //@{ Histo1DPtr _h_eta; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(HRS_1988_I250824); }