Rivet analyses
title: ATLAS_2018_I1707015
Measurement of normalized differential distributions in ttbar+photon production at 13 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1707015
Status: VALIDATED
Authors: - Yichen Li - Andy Buckley - Leah Spiedel Johnson - Neil Warrack
References: - Expt page: ATLAS-TOPQ-2017-14 - arXiv: 1812.01697
Beams: p+ p+
Beam energies: (6500.0, 6500.0)GeV
Run details: - top-quark pair production associated with a photon
Differential cross-sections for the production of a top-quark pair in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 36.1 fb^-1, collected by the ATLAS detector at the LHC in 2015 and 2016 at a centre-of-mass energy of 13 TeV. The measurements are performed in single-lepton and dilepton final states in a fiducial volume. Events with exactly one photon, one or two leptons, a channel-dependent minimum number of jets, and at least one b-jet are selected. Neural network algorithms are used to separate the signal from the backgrounds. The differential cross-sections are measured as a function of photon transverse momentum, photon absolute pseudorapidity, and angular distance between the photon and its closest lepton in both channels, as well azimuthal opening angle and absolute pseudorapidity difference between the two leptons in the dilepton channel.
Source code:ATLAS_2018_I1707015.cc
```c++ // -- C++ --
include "Rivet/Analysis.hh"
include "Rivet/Projections/ChargedFinalState.hh"
include "Rivet/Projections/FastJets.hh"
include "Rivet/Projections/InvisibleFinalState.hh"
include "Rivet/Projections/LeptonFinder.hh"
include "Rivet/Projections/PromptFinalState.hh"
include "Rivet/Projections/VetoedFinalState.hh"
namespace Rivet {
/// @brief ttbar + gamma at 13 TeV class ATLAS_2018_I1707015 : public Analysis { public:
// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2018_I1707015);
// Book histograms and initialise projections before the run
void init() {
// Set default running mode to 3 (all)
_mode = 3;
// Get running mode
if (getOption("LMODE") == "SINGLE") _mode = 1;
if (getOption("LMODE") == "DILEPTON") _mode = 2;
if (getOption("LMODE") == "ALL") _mode = 3;
// All final state particles
const FinalState fs;
// Charged particles for signal photon isolation
ChargedFinalState cfs(fs);
declare(cfs, "CFS");
// Signal photons
PromptFinalState photons(Cuts::abspid == PID::PHOTON && Cuts::pT > 20 * GeV && Cuts::abseta < 2.37,
TauDecaysAs::PROMPT);
declare(photons, "Photons");
// Leptons
PromptFinalState leptons(Cuts::abspid == PID::MUON || Cuts::abspid == PID::ELECTRON,
TauDecaysAs::PROMPT);
// Dress the leptons
FinalState dressPhotons(Cuts::abspid == PID::PHOTON);
Cut lepCuts = (Cuts::abseta < 2.5) && (Cuts::pT > 25 * GeV);
LeptonFinder dressedLeptons(leptons, dressPhotons, 0.1, lepCuts);
declare(dressedLeptons, "Leptons");
// Jet alg input
VetoedFinalState vfs(fs);
// Remove prompt invisibles from jet input
vfs.addVetoOnThisFinalState(InvisibleFinalState(OnlyPrompt::YES, TauDecaysAs::PROMPT));
// Remove prompt dressed muons (muons + associated photons) from jet input
PromptFinalState muons(Cuts::abspid == PID::MUON, TauDecaysAs::PROMPT);
LeptonFinder dressedmuons(muons, dressPhotons, 0.1);
vfs.addVetoOnThisFinalState(dressedmuons);
// Jet clustering
FastJets jets(vfs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::ALL);
declare(jets, "Jets");
// Book histograms
if (_mode == 1 or _mode == 3) { // Single lepton channel
book(_h["sl_ph_pt"], 3, 1, 1); // photon pT
book(_h["sl_ph_eta"], 4, 1, 1); // photon eta
book(_h["sl_ph_l_dR"], 5, 1, 1); // photon-lepton dR
}
if (_mode == 2 or _mode == 3) { // Dilepton channel
book(_h["dl_ph_pt"], 6, 1, 1); // photon pT
book(_h["dl_ph_eta"], 7, 1, 1); // photon eta
book(_h["dl_ph_l_dR"], 8, 1, 1); // min photon-lepton dR
book(_h["dl_l_dEta"], 9, 1, 1); // lepton-lepton dEta
book(_h["dl_l_dPhi"], 10, 1, 1); // lepton-lepton dPhi
}
}
void analyze(const Event& event) {
// Fetch objects
const DressedLeptons& leptons = apply<LeptonFinder>(event, "Leptons").dressedLeptons();
const Particles& photons = apply<PromptFinalState>(event, "Photons").particles();
ChargedFinalState charged = apply<ChargedFinalState>(event, "CFS");
Jets jets = apply<JetFinder>(event, "Jets").jetsByPt(Cuts::abseta < 2.5 && Cuts::pT > 25 * GeV);
// Immediate veto on events without one good photon
if (photons.size() != 1) vetoEvent;
const Particle& photon = photons[0];
// Veto event if photon too close to a lepton
for (const DressedLepton& lep : leptons) {
if (deltaR(lep, photon) < 1.0) vetoEvent;
}
// Overlap removel of jets near leptons
idiscardIfAnyDeltaRLess(jets, leptons, 0.4);
// Overlap removel of jets near isolated photon
const double conePt = sum(charged.particles(deltaRLess(photon, 0.3)), Kin::pT, 0.0);
if (conePt / photon.pT() < 0.1) {
idiscard(jets, deltaRLess(photon, 0.4));
}
// Veto event if photon too close to good jets
for (const Jet& jet : jets) {
if (deltaR(jet, photon) < 0.4) vetoEvent;
}
// Require at least one bjet
unsigned int nbjets = 0;
for (const Jet& jet : jets) {
if (jet.bTagged(Cuts::pT > 5 * GeV)) nbjets += 1;
}
if (nbjets == 0) vetoEvent;
// Fill histos in single lepton channel
if (_mode == 1 || _mode == 3) {
if (jets.size() >= 4 && leptons.size() == 1) {
_h["sl_ph_pt"]->fill(photon.pT() / GeV);
_h["sl_ph_eta"]->fill(photon.abseta());
_h["sl_ph_l_dR"]->fill(deltaR(leptons[0], photon));
}
}
// Fill histos in dilepton channel
if (_mode == 2 || _mode == 3) {
if (jets.size() >= 2 && leptons.size() == 2) {
double deltaRNew;
double deltaRMin = 999.0;
for (const DressedLepton& lep : leptons) {
deltaRNew = deltaR(lep, photon);
if (deltaRNew < deltaRMin) deltaRMin = deltaRNew;
}
_h["dl_ph_pt"]->fill(photon.pT() / GeV);
_h["dl_ph_eta"]->fill(photon.abseta());
_h["dl_ph_l_dR"]->fill(deltaRMin);
_h["dl_l_dEta"]->fill(deltaEta(leptons[0], leptons[1]));
_h["dl_l_dPhi"]->fill(deltaPhi(leptons[0], leptons[1]));
}
}
}
void finalize() {
// Normalise histograms after the run
normalize(_h, 1.0, true);
}
private:
int _mode;
map<string, Histo1DPtr> _h;
};
RIVET_DECLARE_PLUGIN(ATLAS_2018_I1707015); } ```