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## Rivet analyses reference

### D0_2006_S6438750

Inclusive isolated photon cross-section, differential in pT(gamma)
Experiment: D0 (Tevatron Run 2)
Inspire ID: 698784
Status: VALIDATED
Authors:
• Andy Buckley
• Gavin Hesketh
• Frank Siegert
References:
Beams: p- p+
Beam energies: (980.0, 980.0) GeV
Run details:
• ppbar collisions at $\sqrt{s} = 1960$ GeV. Requires gamma + jet (q,qbar,g) hard processes, which for Pythia 6 means MSEL=10 for with MSUB indices 14, 18, 29, 114, 115 enabled.

Measurement of differential cross section for inclusive production of isolated photons in p pbar collisions at $\sqrt{s} = 1.96$ TeV with the D\O detector at the Fermilab Tevatron collider. The photons span transverse momenta 23--300 GeV and have pseudorapidity $|\eta| < 0.9$. Isolated direct photons are probes of pQCD via the annihilation ($q \bar{q} -> \gamma g$) and quark-gluon Compton scattering ($q g -> \gamma q$) processes, the latter of which is also sensitive to the gluon PDF. The initial state radiation / resummation formalisms are sensitive to the resulting photon pT spectrum

Source code: D0_2006_S6438750.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 98 99 100 101 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/LeadingParticlesFinalState.hh" #include "Rivet/Projections/VetoedFinalState.hh" namespace Rivet { /// @brief D0 inclusive isolated photon cross-section vs. \f$p_\perp(gamma) \f$. /// @author Andy Buckley /// @author Gavin Hesketh class D0_2006_S6438750 : public Analysis { public: /// @name Constructors etc. //@{ /// Default constructor. D0_2006_S6438750() : Analysis("D0_2006_S6438750") { } //@} /// @name Analysis methods //@{ void init() { // General FS for photon isolation FinalState fs; declare(fs, "AllFS"); // Get leading photon LeadingParticlesFinalState photonfs(FinalState((Cuts::etaIn(-0.9, 0.9) && Cuts::pT >= 23.0*GeV))); photonfs.addParticleId(PID::PHOTON); declare(photonfs, "LeadingPhoton"); // Book histograms book(_h_pTgamma ,1, 1, 1); } /// Do the analysis void analyze(const Event& event) { // Get the photon const FinalState& photonfs = apply(event, "LeadingPhoton"); if (photonfs.particles().size() != 1) { vetoEvent; } const FourMomentum photon = photonfs.particles().front().momentum(); // Isolate photon by ensuring that a 0.4 cone around it contains less than 10% of the photon's energy double E_P = photon.E(); double eta_P = photon.eta(); double phi_P = photon.phi(); double econe = 0.0; for (const Particle& p : apply(event, "AllFS").particles()) { if (deltaR(eta_P, phi_P, p.eta(), p.phi()) < 0.4) { econe += p.E(); if (econe/E_P > 1.1) { vetoEvent; } } } // Fill histo _h_pTgamma->fill(photon.pT()); } // Finalize void finalize() { const double lumi_gen = sumOfWeights()/crossSection(); // Divide by effective lumi, plus rapidity bin width of 1.8 scale(_h_pTgamma, 1/lumi_gen * 1/1.8); } //@} private: /// @name Histograms //@{ Histo1DPtr _h_pTgamma; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(D0_2006_S6438750); }