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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
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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<FinalState>(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<FinalState>(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);
}
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