Rivet analyses referenceATLAS_2016_I1478355Measurement of the bbar dijet dijet cross section at 7 TeVExperiment: ATLAS (LHC) Inspire ID: 1478355 Status: VALIDATED Authors:
Beam energies: (3500.0, 3500.0) GeV Run details:
The dijet production cross section for jets containing a $b$-hadron ($b$-jets) has been measured in proton-proton collisions with a centre-of-mass energy of $\sqrt{s} = 7$ TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2 fb$^{-1}$. The cross section is measured for events with two identified $b$-jets with a transverse momentum $p_\mathrm{T} > 20$GeV and a minimum separation in the $\eta$-$\phi$ plane of $\Delta R$ = 0.4. At least one of the jets in the event is required to have $p_\mathrm{T} > 270$GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the $b$-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization. Source code: ATLAS_2016_I1478355.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FastJets.hh"
4#include "Rivet/Projections/HeavyHadrons.hh"
5
6namespace Rivet {
7
8
9 /// @brief Measurement of the bbar dijet dijet cross section at 7 TeV
10 class ATLAS_2016_I1478355 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2016_I1478355);
15
16 /// @name Analysis methods
17 ///@{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
22 // Initialise and register projections
23 FinalState fs(Cuts::abseta < 3.2);
24 FastJets fj(fs, JetAlg::ANTIKT, 0.4);
25 fj.useInvisibles();
26 declare(fj, "Jets");
27 declare(HeavyHadrons(Cuts::abseta < 3.2 && Cuts::pT > 5*GeV), "BHadrons");
28
29 book(_h["m_bb"], 1, 1, 1);
30 book(_h["Delta_phi"], 2, 1, 1);
31 book(_h["y_diff"], 3, 1, 1);
32 book(_h["Delta_R"], 4, 1, 1);
33 book(_h["pT_bb"], 5, 1, 1);
34 book(_h["y_B"], 6, 1, 1);
35 }
36
37
38 /// Perform the per-event analysis
39 void analyze(const Event& event) {
40
41 // Retrieve clustered jets, sorted by pT, with a minimum pT cut
42 const Jets& jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 20*GeV);
43 const Particles& bHadrons = apply<HeavyHadrons>(event, "BHadrons").bHadrons();
44
45 if (jets.size() < 1) vetoEvent;
46 if (jets[0].pT() > 270*GeV){
47
48 Jets foundBjets;
49 for (const Jet& j : jets){
50 for (const Particle& b : bHadrons){
51 if ((deltaR(j, b) < 0.3) && (j.pT() > 20*GeV) && (fabs(j.eta()) < 2.5)) foundBjets.push_back(j);
52 }
53 }
54
55 Jet firstBjet;
56 Jet secondBjet;
57 bool bJetPair = false;
58 for (const Jet& b1 : foundBjets){
59 for (const Jet& b2 : foundBjets){
60 if(deltaR(b1, b2) > 0.4){
61 bJetPair = true;
62 firstBjet = b1;
63 secondBjet = b2;
64 break;
65 }
66 }
67 if (bJetPair) break;
68 }
69
70 if (bJetPair) {
71 const double mass = (firstBjet.momentum() + secondBjet.momentum()).mass();
72 _h["m_bb"]->fill(mass/GeV);
73 const double Delta_phi = deltaPhi(firstBjet.phi(), secondBjet.phi());
74 _h["Delta_phi"]->fill(Delta_phi);
75 const double y_diff = fabs(firstBjet.rapidity() - secondBjet.rapidity())/2;
76 _h["y_diff"]->fill(y_diff);
77 const double Delta_R = deltaR(firstBjet.momentum(), secondBjet.momentum());
78 _h["Delta_R"]->fill(Delta_R);
79 const double pT = (firstBjet.momentum() + secondBjet.momentum()).pT();
80 _h["pT_bb"]->fill(pT/GeV);
81 const double y_B = (firstBjet.rapidity() + secondBjet.rapidity())/2;
82 _h["y_B"]->fill(y_B);
83 }
84 }
85 }
86
87 /// Normalise histograms etc., after the run
88 void finalize() {
89
90 const double xsec = crossSectionPerEvent()/picobarn;
91 scale(_h, xsec);
92 }
93
94 ///@}
95
96 /// @name Histograms
97 ///@{
98 map<string, Histo1DPtr> _h;
99 ///@}
100
101 };
102
103 RIVET_DECLARE_PLUGIN(ATLAS_2016_I1478355);
104}
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