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ATLAS_2016_I1487726

Collinear W emissions at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1487726
Status: VALIDATED
Authors:
  • Marek Schoenherr
  • Miles Wu
  • Chris Gutschow
References: Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • 8 TeV $pp \to W+\text{jets} \to \mu\nu+\text{jets}$.

The $W$ boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton-proton collisions at a centre-of-mass energy $\sqrt{s}=8$ TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The focus is on the contributions to $W+$jets processes from real $W$ emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic $W$ decay.

Source code: ATLAS_2016_I1487726.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4#include "Rivet/Projections/LeptonFinder.hh"
 5#include "Rivet/Projections/FastJets.hh"
 6
 7namespace Rivet {
 8
 9
10    /// Collinear W emissions at 8 TeV
11    class ATLAS_2016_I1487726 : public Analysis {
12    public:
13
14    /// Constructor
15    RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2016_I1487726);
16
17
18        /// @name Analysis methods
19        /// @{
20
21        /// Book histograms and initialise projections before the run
22        void init() {
23
24            _mode = 0;
25            if ( getOption("LMODE") == "EL" )  _mode = 1;
26
27            // These really should include non-prompt leptons/photons
28            FinalState mufs(Cuts::abspid == PID::MUON);
29            FinalState elfs(Cuts::abspid == PID::ELECTRON);
30            FinalState phs(Cuts::abspid == PID::PHOTON);
31
32            Cut lep_fid = (Cuts::abseta < 2.4 && Cuts::pT >= 25*GeV);
33            LeptonFinder dlep(_mode? elfs : mufs, phs, 0.1, lep_fid);
34            declare(dlep, "LeptonFinder");
35
36            FastJets fj(FinalState(), JetAlg::ANTIKT, 0.4, JetMuons::NONE, JetInvisibles::NONE);
37            declare(fj, "AntiKt4Jets");
38
39            book(h_mu_jet_dr,          2, 1, 1);
40            book(h_mu_jet_dr_pt500600, 4, 1, 1);
41            book(h_mu_jet_dr_pt650,    5, 1, 1);
42        }
43
44
45        /// Perform the per-event analysis
46        void analyze(const Event& event) {
47
48          const DressedLeptons leptons = apply<LeptonFinder>(event, "LeptonFinder").dressedLeptons();
49          const Jets jets = apply<FastJets>(event, "AntiKt4Jets").jetsByPt(Cuts::pT >= 100*GeV && Cuts::abseta <= 2.1);
50
51          if (leptons.size() != 1)       vetoEvent;
52          if (jets.size() < 1)           vetoEvent;
53          if (jets[0].pt() < 500.0*GeV)  vetoEvent;
54
55          // find closest jet to the lepton.
56          Jet jet;
57          double drmin = 999;
58          for (const Jet &j : jets) {
59            double dr = deltaR(leptons[0], j);
60            if (dr < drmin) {
61                drmin = dr;
62                jet = j;
63            }
64          }
65
66          h_mu_jet_dr->fill(drmin);
67          if (jets[0].pT() > 650*GeV)  h_mu_jet_dr_pt650->fill(drmin);
68          else if (jets[0].pT() > 500*GeV && jets[0].pT() < 600*GeV) {
69            h_mu_jet_dr_pt500600->fill(drmin);
70          }
71        }
72
73        /// Normalise histograms etc., after the run
74        void finalize() {
75          const double sf = crossSection() / femtobarn / sumOfWeights();
76          scale(h_mu_jet_dr, sf);
77          scale(h_mu_jet_dr_pt500600, sf);
78          scale(h_mu_jet_dr_pt650, sf);
79        }
80
81        /// @}
82
83    protected:
84
85        size_t _mode;
86
87    private:
88
89        /// @name Histograms
90        /// @{
91        Histo1DPtr h_mu_jet_dr;
92        Histo1DPtr h_mu_jet_dr_pt500600;
93        Histo1DPtr h_mu_jet_dr_pt650;
94        /// @}
95  };
96
97
98  RIVET_DECLARE_PLUGIN(ATLAS_2016_I1487726);
99}