Rivet analyses referenceATLAS_2014_I1268975High-mass dijet cross sectionExperiment: ATLAS (LHC) Inspire ID: 1268975 Status: VALIDATED Authors:
Beam energies: (3500.0, 3500.0) GeV Run details:
Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5/fb, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross sections are compared with next-to-leading-order perturbative QCD calculations by NLOJET++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a parton-shower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model. Source code: ATLAS_2014_I1268975.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/FastJets.hh"
5
6namespace Rivet {
7
8
9 /// Jet mass as a function of ystar
10 class ATLAS_2014_I1268975 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2014_I1268975);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22
23 const FinalState fs;
24 declare(fs,"FinalState");
25
26 FastJets fj04(fs, JetAlg::ANTIKT, 0.4);
27 fj04.useInvisibles();
28 declare(fj04, "AntiKT04");
29
30 FastJets fj06(fs, JetAlg::ANTIKT, 0.6);
31 fj06.useInvisibles();
32 declare(fj06, "AntiKT06");
33
34 vector<double> ystarbins{ 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0};
35
36 size_t massDsOffset(0);
37 for (size_t alg = 0; alg < 2; ++alg) {
38 book(_mass[alg], ystarbins);
39 for (auto& b : _mass[alg]->bins()) {
40 book(b, 1+massDsOffset, 1, b.index());
41 }
42 ++massDsOffset;
43 }
44 }
45
46
47 /// Perform the per-event analysis
48 void analyze(const Event& event) {
49 Jets jetAr[2];
50 jetAr[AKT4] = apply<FastJets>(event, "AntiKT04").jetsByPt(Cuts::pT > 50*GeV);
51 jetAr[AKT6] = apply<FastJets>(event, "AntiKT06").jetsByPt(Cuts::pT > 50*GeV);
52
53 // Loop over jet "radii" used in analysis
54 for (size_t alg = 0; alg < 2; ++alg) {
55
56 // Identify dijets
57 vector<FourMomentum> leadjets;
58 for (const Jet& jet : jetAr[alg]) {
59 if (jet.absrap() < 3.0 && leadjets.size() < 2) {
60 if (leadjets.empty() && jet.pT() < 100*GeV) continue;
61 leadjets.push_back(jet.momentum());
62 }
63 }
64
65 // Make sure we have a leading jet with pT > 100 GeV and a second to leading jet with pT > 50 GeV
66 if (leadjets.size() < 2) {
67 MSG_DEBUG("Could not find two suitable leading jets");
68 continue;
69 }
70
71 const double y1 = leadjets[0].rapidity();
72 const double y2 = leadjets[1].rapidity();
73 const double ystar = fabs(y1-y2) / 2.;
74 const double m = (leadjets[0] + leadjets[1]).mass();
75
76 // Fill mass histogram
77 _mass[alg]->fill(ystar, m/TeV);
78 }
79 }
80
81
82 /// Normalise histograms etc., after the run
83 void finalize() {
84 scale(_mass, crossSectionPerEvent()/picobarn);
85 divByGroupWidth(_mass);
86 }
87
88 /// @}
89
90
91 private:
92
93 // Data members like post-cuts event weight counters go here
94 enum Alg { AKT4=0, AKT6=1 };
95
96 /// The di-jet mass spectrum binned in rapidity for akt6 and akt4 jets (array index is jet type from enum above)
97 Histo1DGroupPtr _mass[2];
98
99 };
100
101
102 RIVET_DECLARE_PLUGIN(ATLAS_2014_I1268975);
103
104}
|