Rivet analyses referenceATLAS_2019_I1764342Z(ll)y cross-section at 13 TeVExperiment: ATLAS (LHC) Inspire ID: 1764342 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
The production of a prompt photon in association with a Z boson is studied in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$13 TeV. The analysis uses a data sample with an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector at the LHC from 2015 to 2018. The production cross-section for the process $pp \rightarrow \ell^+ \ell^- + \gamma + X$ ($\ell=e,\mu$) is measured within a fiducial phase-space region defined by kinematic requirements on the photon and the leptons, and by isolation requirements on the photon. An experimental precision of $2.9\%$ is achieved for the fiducial cross-section. Differential cross-sections are measured as a function of each of six kinematic variables characterising the $\ell^+\ell^-\gamma$ system. The data are compared with theoretical predictions based on next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations. The impact of next-to-leading-order electroweak corrections is also considered. Source code: ATLAS_2019_I1764342.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/VetoedFinalState.hh"
5#include "Rivet/Projections/LeptonFinder.hh"
6#include "Rivet/Projections/PromptFinalState.hh"
7#include "Rivet/Projections/InvisibleFinalState.hh"
8
9namespace Rivet {
10
11
12 /// @brief Z(ll)y cross-section at 13 TeV
13 class ATLAS_2019_I1764342 : public Analysis {
14 public:
15
16 /// Constructor
17 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2019_I1764342);
18
19 /// @name Analysis methods
20 /// @{
21
22 /// Book histograms and initialise projections before the run
23 void init() {
24
25 // get option
26 _mode = 0;
27 if ( getOption("LMODE") == "EL" ) _mode = 1;
28 if ( getOption("LMODE") == "MU" ) _mode = 2;
29
30 // Prompt photons
31 const PromptFinalState photon_fs(Cuts::abspid == PID::PHOTON && Cuts::pT > 30*GeV && Cuts::abseta < 2.37);
32 declare(photon_fs, "Photons");
33
34 // Prompt leptons
35 const PromptFinalState bareelectron_fs = Cuts::abspid == PID::ELECTRON;
36 const PromptFinalState baremuon_fs = Cuts::abspid == PID::MUON;
37
38 // Dressed leptons
39 const FinalState allphoton_fs(Cuts::abspid == PID::PHOTON); // photons used for lepton dressing
40 const Cut leptoncut = Cuts::pT > 25*GeV && Cuts::abseta < 2.47;
41 const LeptonFinder dressedelectron_fs(bareelectron_fs, allphoton_fs, 0.1, leptoncut);
42 const LeptonFinder dressedmuon_fs(baremuon_fs, allphoton_fs, 0.1, leptoncut);
43
44 declare(dressedelectron_fs, "Electrons");
45 declare(dressedmuon_fs, "Muons");
46
47 // FS excluding the leading photon
48 VetoedFinalState vfs;
49 vfs.addVetoOnThisFinalState(photon_fs);
50 vfs.addVetoOnThisFinalState(dressedmuon_fs);
51 vfs.addVetoOnThisFinalState(InvisibleFinalState());
52 declare(vfs, "isolatedFS");
53
54 // Histograms
55 book(_h["EgammaT"], 2, 1, 1); // dSigma / dE^gamma_T
56 book(_h["etagamma"], 3, 1, 1);
57 book(_h["mZgamma"], 4, 1, 1); // dSigma / dm^{Zgamma}
58 book(_h["EZgammaT"], 5, 1, 1);
59 book(_h["dPhiZgamma"], 6, 1, 1);
60 book(_h["ETbyMZgamma"], 7, 1, 1);
61 }
62
63
64 /// Perform the per-event analysis
65 void analyze(const Event& event) {
66 // Get objects
67 Particles electrons = apply<LeptonFinder>(event, "Electrons").particlesByPt();
68 Particles muons = apply<LeptonFinder>(event, "Muons").particlesByPt();
69 const Particles& photons = apply<PromptFinalState>(event, "Photons").particlesByPt();
70
71 if (photons.empty()) vetoEvent;
72 if (electrons.size() < 2 && muons.size() < 2) vetoEvent;
73
74 if (_mode == 1 && muons.size()) vetoEvent;
75 if (_mode == 2 && electrons.size()) vetoEvent;
76
77 Particles lep;
78 // Sort the dressed leptons by pt
79 if (electrons.size() >= 2) {
80 lep.push_back(electrons[0]);
81 lep.push_back(electrons[1]);
82 } else {
83 lep.push_back(muons[0]);
84 lep.push_back(muons[1]);
85 }
86 if (lep[0].Et() < 30*GeV) vetoEvent;
87 double mll = (lep[0].momentum() + lep[1].momentum()).mass();
88 if (mll < 40*GeV) vetoEvent;
89
90 Particles selectedPh;
91 Particles fs = apply<VetoedFinalState>(event, "isolatedFS").particles();
92 for (const Particle& ph : photons) {
93 // check photon isolation
94 double coneEnergy(0.0);
95 for (const Particle& p : fs) {
96 if ( deltaR(ph, p) < 0.2 ) coneEnergy += p.Et();
97 }
98 if (coneEnergy / ph.Et() > 0.07 ) continue;
99 if (deltaR(ph, lep[0]) < 0.4) continue;
100 if (deltaR(ph, lep[1]) < 0.4) continue;
101 selectedPh.push_back(ph);
102 }
103
104 if (selectedPh.size()<1) vetoEvent;
105 double mlly = (lep[0].momentum() + lep[1].momentum() + selectedPh[0].momentum()).mass();
106 if (mll + mlly <= 182*GeV) vetoEvent;
107
108 double ptlly = (lep[0].momentum() + lep[1].momentum() + selectedPh[0].momentum()).pT();
109 double dphilly = deltaPhi((lep[0].momentum() + lep[1].momentum()).phi(), selectedPh[0].momentum().phi());
110
111 // Fill plots
112 _h["EgammaT"]->fill(selectedPh[0].pT()/GeV);
113 _h["etagamma"]->fill(selectedPh[0].abseta());
114 _h["mZgamma"]->fill(mlly/GeV);
115 _h["EZgammaT"]->fill(ptlly/GeV);
116 _h["dPhiZgamma"]->fill(dphilly/pi);
117 _h["ETbyMZgamma"]->fill(ptlly/mlly);
118 }
119
120
121 /// Normalise histograms etc., after the run
122 void finalize() {
123 double sf = crossSection()/femtobarn/sumOfWeights();
124 if (_mode == 0) sf *= 0.5;
125 scale(_h, sf);
126 scale(_h["dPhiZgamma"], 1.0/pi);
127 }
128
129 /// @}
130
131
132 private:
133
134 /// Mode flag
135 size_t _mode;
136
137 /// Histograms
138 map<string,Histo1DPtr> _h;
139
140 };
141
142
143 RIVET_DECLARE_PLUGIN(ATLAS_2019_I1764342);
144
145}
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