Rivet analyses
title: D0_2008_I782968
Isolated $\gamma$ + jet cross-sections, differential in pT($\gamma$) for various $y$ bins
Experiment: D0 (Tevatron Run 2)
Inspire ID: 782968
Status: VALIDATED
Authors: - Andy Buckley - Gavin Hesketh - Frank Siegert
References: - Phys.Lett.B666:435-445,2008 - DOI: 10.1016/j.physletb.2008.06.076 - arXiv: 0804.1107
Beams: p- p+
Beam energies: (980.0, 980.0)GeV
Run details: - Produce only gamma + jet ($q,\bar{q},g$) hard processes (for Pythia 6, this means MSEL=10 and MSUB indices 14, 29 & 115 enabled). The lowest bin edge is at 30 GeV, so a kinematic pTmin cut is probably required to fill the histograms.
The process $p \bar{p}$ -> photon + jet + X as studied by the D0 detector at the Fermilab Tevatron collider at center-of-mass energy $\sqrt{s} = 1.96~\TeV$. Photons are reconstructed in the central rapidity region $|y_\gamma| < 1.0$ with transverse momenta in the range 30--400~GeV, while jets are reconstructed in either the central $|y_\text{jet}| < 0.8$ or forward $1.5 < |y_\text{jet}| < 2.5$ rapidity intervals with $\pT^\text{jet} > 15~\GeV$. The differential cross section $\mathrm{d}^3 \sigma / \mathrm{d}{\pT^\gamma} \mathrm{d}{y_\gamma} \mathrm{d}{y_\text{jet}}$ is measured as a function of $\pT^\gamma$ in four regions, differing by the relative orientations of the photon and the jet. MC predictions have trouble with simultaneously describing the measured normalization and $\pT^\gamma$ dependence of the cross section in any of the four measured regions.
Source code:D0_2008_I782968.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 Measurement of isolated gamma + jet + X differential cross-sections /// /// Inclusive isolated gamma + jet cross-sections, differential in pT(gamma), for /// various photon and jet rapidity bins. /// /// @author Andy Buckley /// @author Gavin Hesketh class D0_2008_I782968 : public Analysis { public:
RIVET_DEFAULT_ANALYSIS_CTOR(D0_2008_I782968);
/// @name Analysis methods
/// @{
/// Set up projections and book histograms
void init() {
// General FS
FinalState fs;
declare(fs, "FS");
// Get leading photon
LeadingParticlesFinalState photonfs(FinalState((Cuts::etaIn(-1.0, 1.0) && Cuts::pT >= 30.0 * GeV)));
photonfs.addParticleId(PID::PHOTON);
declare(photonfs, "LeadingPhoton");
// FS excluding the leading photon
VetoedFinalState vfs(fs);
vfs.addVetoOnThisFinalState(photonfs);
declare(vfs, "JetFS");
// Jets
FastJets jetpro(vfs, JetAlg::D0ILCONE, 0.7);
declare(jetpro, "Jets");
// Histograms
book(_h_central_same_cross_section, 1, 1, 1);
book(_h_central_opp_cross_section, 2, 1, 1);
book(_h_forward_same_cross_section, 3, 1, 1);
book(_h_forward_opp_cross_section, 4, 1, 1);
// Ratio histos to be filled by divide()
book(_h_cen_opp_same, 5, 1, 1);
book(_h_fwd_opp_same, 8, 1, 1);
// Ratio histos to be filled manually, since the num/denom inputs don't match
book(_h_cen_same_fwd_same, 6, 1, 1);
book(_h_cen_opp_fwd_same, 7, 1, 1);
book(_h_cen_same_fwd_opp, 9, 1, 1);
book(_h_cen_opp_fwd_opp, 10, 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 7% of the photon's energy
double egamma = photon.E();
double eta_P = photon.eta();
double phi_P = photon.phi();
double econe = 0.0;
for (const Particle& p : apply<FinalState>(event, "JetFS").particles()) {
if (deltaR(eta_P, phi_P, p.eta(), p.phi()) < 0.4) {
econe += p.E();
// Veto as soon as E_cone gets larger
if (econe / egamma > 0.07) {
MSG_DEBUG("Vetoing event because photon is insufficiently isolated");
vetoEvent;
}
}
}
Jets jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 15.0 * GeV);
if (jets.empty()) vetoEvent;
FourMomentum leadingJet = jets[0].momentum();
if (deltaR(eta_P, phi_P, leadingJet.eta(), leadingJet.phi()) < 0.7) {
vetoEvent;
}
int photon_jet_sign = sign(leadingJet.rapidity() * photon.rapidity());
// Veto if leading jet is outside plotted rapidity regions
const double abs_y1 = fabs(leadingJet.rapidity());
if (inRange(abs_y1, 0.8, 1.5) || abs_y1 > 2.5) {
MSG_DEBUG("Leading jet falls outside acceptance range; |y1| = " << abs_y1);
vetoEvent;
}
// Fill histos
if (fabs(leadingJet.rapidity()) < 0.8) {
Histo1DPtr h = (photon_jet_sign >= 1) ? _h_central_same_cross_section : _h_central_opp_cross_section;
h->fill(photon.pT());
}
else if (inRange(fabs(leadingJet.rapidity()), 1.5, 2.5)) {
Histo1DPtr h = (photon_jet_sign >= 1) ? _h_forward_same_cross_section : _h_forward_opp_cross_section;
h->fill(photon.pT());
}
}
/// Finalize
void finalize() {
const double lumi_gen = sumOfWeights() / crossSection() / picobarn;
const double dy_photon = 2.0;
const double dy_jet_central = 1.6;
const double dy_jet_forward = 2.0;
// Cross-section ratios (6 plots)
// Central/central and forward/forward ratios
divide(_h_central_opp_cross_section, _h_central_same_cross_section, _h_cen_opp_same);
divide(_h_forward_opp_cross_section, _h_forward_same_cross_section, _h_fwd_opp_same);
// Central/forward ratio combinations
/// @note The central/forward histo binnings are not the same! Hence the need to do these by hand :-(
for (size_t i = 1; i < _h_cen_same_fwd_same->numBins() + 1; ++i) {
const auto& cen_same_bini = _h_central_same_cross_section->bin(i);
const auto& cen_opp_bini = _h_central_opp_cross_section->bin(i);
const auto& fwd_same_bini = _h_central_same_cross_section->bin(i);
const auto& fwd_opp_bini = _h_central_opp_cross_section->bin(i);
_h_cen_same_fwd_same->bin(i).set(_safediv(cen_same_bini.sumW(), fwd_same_bini.sumW(), 0),
add_quad(cen_same_bini.relErrW(), fwd_same_bini.relErrW()));
_h_cen_opp_fwd_same->bin(i).set(_safediv(cen_opp_bini.sumW(), fwd_same_bini.sumW(), 0),
add_quad(cen_opp_bini.relErrW(), fwd_same_bini.relErrW()));
_h_cen_same_fwd_opp->bin(i).set(_safediv(cen_same_bini.sumW(), fwd_opp_bini.sumW(), 0),
add_quad(cen_same_bini.relErrW(), fwd_opp_bini.relErrW()));
_h_cen_opp_fwd_opp->bin(i).set(_safediv(cen_opp_bini.sumW(), fwd_opp_bini.sumW(), 0),
add_quad(cen_opp_bini.relErrW(), fwd_opp_bini.relErrW()));
}
// Use generator cross section for remaining histograms
// Each of these needs the additional factor 2 because the
// y_photon * y_jet requirement reduces the corresponding 2D "bin width"
// by a factor 1/2.
scale(_h_central_same_cross_section, 2.0 / lumi_gen * 1.0 / dy_photon * 1.0 / dy_jet_central);
scale(_h_central_opp_cross_section, 2.0 / lumi_gen * 1.0 / dy_photon * 1.0 / dy_jet_central);
scale(_h_forward_same_cross_section, 2.0 / lumi_gen * 1.0 / dy_photon * 1.0 / dy_jet_forward);
scale(_h_forward_opp_cross_section, 2.0 / lumi_gen * 1.0 / dy_photon * 1.0 / dy_jet_forward);
}
/// @}
private:
// A local scope function for division, handling the div-by-zero case
/// @todo Why isn't the math divide() function being found?
double _safediv(double a, double b, double result_if_err) {
return (b != 0) ? a / b : result_if_err;
}
/// @name Histograms
/// @{
Histo1DPtr _h_central_same_cross_section;
Histo1DPtr _h_central_opp_cross_section;
Histo1DPtr _h_forward_same_cross_section;
Histo1DPtr _h_forward_opp_cross_section;
Estimate1DPtr _h_cen_opp_same;
Estimate1DPtr _h_fwd_opp_same;
Estimate1DPtr _h_cen_same_fwd_same;
Estimate1DPtr _h_cen_opp_fwd_same;
Estimate1DPtr _h_cen_same_fwd_opp;
Estimate1DPtr _h_cen_opp_fwd_opp;
/// @}
};
RIVET_DECLARE_ALIASED_PLUGIN(D0_2008_I782968, D0_2008_S7719523);
} ```
Aliases: - D0_2008_S7719523