Rivet analyses

title: CDF_1993_I354237

Angular distribution of prompt photon

Experiment: CDF (Tevatron Run 1)

Inspire ID: 354237

Status: UNVALIDATED

Authors: - Frank Siegert

References: - Phys.Rev.Lett.71:679-683,1993 - DOI: 10.1103/PhysRevLett.71.679

Beams: p- p+

Beam energies: (900.0, 900.0)GeV

Run details: - All prompt photon production processes in $p \bar{p}$ at 1800 GeV. Hadronisation should be switched off, because non-prompt photon production has been corrected for.

Data taken with the Collider Detector at Fermilab (CDF) during the 1988-1989 run of the Tevatron are used to measure the distribution of the center-of-mass (rest frame of the initial state partons) angle between isolated prompt photons and the beam direction. WARNING --- Implemented is the simplified c.m. definition given in the paper. The rise of the data and the MC predictions presented in the latter could not be reproduced.

Source code:CDF_1993_I354237.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/LeadingParticlesFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// @brief CDF angular distribution of prompt photon class CDF_1993_I354237 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(CDF_1993_I354237);


void init() {

  // The photon selection has been corrected to pTmin=22 GeV (vs. 23 in the trigger)
  LeadingParticlesFinalState photonfs(FinalState(Cuts::abseta < 0.9 && Cuts::pT >= 22 * GeV));
  photonfs.addParticleId(PID::PHOTON);
  declare(photonfs, "LeadingPhoton");

  // FS excluding the leading photon
  VetoedFinalState vfs(FinalState(Cuts::abseta < 4.2));
  vfs.addVetoOnThisFinalState(photonfs);
  declare(vfs, "VFS");

  // Jets
  declare(FastJets(vfs, JetAlg::CDFJETCLU, 0.7), "Jets");

  book(_h_costheta, 1, 1, 1);
}


void analyze(const Event& event) {

  Particles photons = apply<LeadingParticlesFinalState>(event, "LeadingPhoton").particles();
  if (photons.size() != 1 || photons[0].pT() > 45.0 * GeV) vetoEvent;
  FourMomentum leadingPhoton = photons[0].momentum();
  double eta_P = leadingPhoton.eta();
  double phi_P = leadingPhoton.phi();

  // photon isolation: less than 2 GeV EM E_T
  double Etsum = 0.0;
  for (const Particle& p : apply<VetoedFinalState>(event, "VFS").particles()) {
    if (p.charge() != 0 && deltaR(eta_P, phi_P, p.eta(), p.phi()) < 0.7) Etsum += p.Et();
  }
  if (Etsum > 2 * GeV) vetoEvent;

  FourMomentum jetsum;
  Jets jets = apply<FastJets>(event, "Jets").jets(Cuts::pT > 10 * GeV, cmpMomByPt);

  // Require at least one jet with pT>10 GeV
  if (jets.size() == 0) vetoEvent;

  // Require the leading jet to be in the opposite (phi) hemisphere w.r.t. the photon
  if (jets[0].phi() - phi_P <= M_PI) vetoEvent;

  // sum all jets in the opposite hemisphere in phi from the photon
  for (const Jet& jet : jets) {
    if (fabs(jet.phi() - phi_P) > M_PI) jetsum += jet.momentum();
  }

  // c.m. cuts, see Table 1
  double etaboost = (jetsum.eta() + eta_P) / 2.;
  if (!inRange(etaboost, -1.2, 1.2)) vetoEvent;

  double etastar = (jetsum.eta() - eta_P) / 2.;
  if (!inRange(etastar, -1.1, 1.1)) vetoEvent;

  double pstar = photons[0].pT() * cosh(etastar);
  if (!inRange(pstar, 27.8, 47.0)) vetoEvent;

  const double costheta = fabs(tanh((eta_P - jetsum.eta()) / 2.0));
  if (!inRange(costheta, 0., 0.8)) vetoEvent;

  // Fill histo
  _h_costheta->fill(costheta);
}


void finalize() {
  /// @todo Take fixed norm direct from ref histo
  normalize(_h_costheta, 1.4271); // fixed norm ok
}

private:

Histo1DPtr _h_costheta;

};

RIVET_DECLARE_ALIASED_PLUGIN(CDF_1993_I354237, CDF_1993_S2742446);

} ```

Aliases: - CDF_1993_S2742446