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ATLAS_2017_I1609253

Multijet transverse energy-energy correlations (TEEC) at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1609253
Status: VALIDATED
Authors:
  • Javier Llorente Merino
  • Christian Gutschow
References: Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • p p -> j j + X at 8 TeV

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to $\sqrt{s} = 8$ TeV proton-proton collisions with an integrated luminosity of 20.2 fb$^{-1}$. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of $\alpha_\text{s}(\mu)$ predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields $\alpha_\text{s}(m_Z) = 0.1162\pm 0.0011\text{(exp.)}^{+0.0084}_{-0.0070}\text{(theo.)}$, while a global fit to the asymmetry distributions yields a value of $\alpha_\text{s}(m_Z) = 0.1196\pm 0.0013\text{(exp.)}^{+0.0075}_{-0.0045}\text{(theo.)}$.

Source code: ATLAS_2017_I1609253.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  /// @brief Multijet transverse energy-energy correlations (TEEC) at 8 TeV
 10  class ATLAS_2017_I1609253 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2017_I1609253);
 15
 16
 17    /// Initialization, called once before running
 18    void init() {
 19
 20      // Projections
 21      const FastJets jets(FinalState(), FastJets::ANTIKT, 0.4, JetAlg::Muons::ALL, JetAlg::Invisibles::ALL);
 22      declare(jets, "Jets");
 23
 24      // Book histograms
 25      book(_hist_EEC1 ,  1, 1, 1);
 26      book(_hist_AEEC1,  2, 1, 1);
 27      book(_hist_EEC2 ,  3, 1, 1);
 28      book(_hist_AEEC2,  4, 1, 1);
 29      book(_hist_EEC3 ,  5, 1, 1);
 30      book(_hist_AEEC3,  6, 1, 1);
 31      book(_hist_EEC4 ,  7, 1, 1);
 32      book(_hist_AEEC4,  8, 1, 1);
 33      book(_hist_EEC5 ,  9, 1, 1);
 34      book(_hist_AEEC5, 10, 1, 1);
 35      book(_hist_EEC6 , 11, 1, 1);
 36      book(_hist_AEEC6, 12, 1, 1);
 37    }
 38
 39
 40    void analyze(const Event& event) {
 41
 42      const Jets& jets = applyProjection<FastJets>(event, "Jets").jetsByPt(Cuts::abseta < 2.5 && Cuts::pT > 100*GeV);
 43      if (jets.size() < 2)  vetoEvent;
 44
 45      double sumPt12 = jets[0].pt() + jets[1].pt();
 46      if (sumPt12 < 800*GeV)  vetoEvent;
 47
 48      double sumEt = 0.;
 49      for (const Jet& j : jets) sumEt += j.Et();
 50
 51      for (const Jet& j1 : jets) {
 52        double et1 = j1.Et();
 53
 54        for (const Jet& j2 : jets) {
 55          double et2 = j2.Et();
 56
 57          double etWeight = et1*et2/(sumEt*sumEt);
 58          double dPhi = deltaPhi(j1, j2);
 59          double cosPhi = cos(dPhi);
 60          if (cos(dPhi) == 1.0)  cosPhi = 0.9999;
 61
 62          if (sumPt12 >  800*GeV && sumPt12 <=  850*GeV)  _hist_EEC1->fill(cosPhi, etWeight);
 63          if (sumPt12 >  850*GeV && sumPt12 <=  900*GeV)  _hist_EEC2->fill(cosPhi, etWeight);
 64          if (sumPt12 >  900*GeV && sumPt12 <= 1000*GeV)  _hist_EEC3->fill(cosPhi, etWeight);
 65          if (sumPt12 > 1000*GeV && sumPt12 <= 1100*GeV)  _hist_EEC4->fill(cosPhi, etWeight);
 66          if (sumPt12 > 1100*GeV && sumPt12 <= 1400*GeV)  _hist_EEC5->fill(cosPhi, etWeight);
 67          if (sumPt12 > 1400*GeV)  _hist_EEC6->fill(cosPhi, etWeight);
 68        }
 69      }
 70    }
 71
 72
 73    void finalize() {
 74
 75      normalize(_hist_EEC1);
 76      normalize(_hist_EEC2);
 77      normalize(_hist_EEC3);
 78      normalize(_hist_EEC4);
 79      normalize(_hist_EEC5);
 80      normalize(_hist_EEC6);
 81
 82      vector<Point2D> points1, points2, points3, points4, points5, points6;
 83      size_t nBins = _hist_EEC1->numBins();
 84      for (size_t k = 0; k < nBins/2; ++k) {
 85        double x = _hist_EEC1->bin(k).midpoint(); double ex = _hist_EEC1->bin(k).xWidth()/2;
 86
 87        double y1 = _hist_EEC1->bin(k).height() - _hist_EEC1->bin(nBins-(k+1)).height();
 88        double ey1 = sqrt( pow(_hist_EEC1->bin(k).heightErr(),2) + pow(_hist_EEC1->bin(nBins-(k+1)).heightErr(),2) );
 89        points1.push_back(Point2D(x,y1,ex,ey1));
 90
 91        double y2 = _hist_EEC2->bin(k).height() - _hist_EEC2->bin(nBins-(k+1)).height();
 92        double ey2 = sqrt( pow(_hist_EEC2->bin(k).heightErr(),2) + pow(_hist_EEC2->bin(nBins-(k+1)).heightErr(),2) );
 93        points2.push_back(Point2D(x,y2,ex,ey2));
 94
 95        double y3 = _hist_EEC3->bin(k).height() - _hist_EEC3->bin(nBins-(k+1)).height();
 96        double ey3 = sqrt( pow(_hist_EEC3->bin(k).heightErr(),2) + pow(_hist_EEC3->bin(nBins-(k+1)).heightErr(),2) );
 97        points3.push_back(Point2D(x,y3,ex,ey3));
 98
 99        double y4 = _hist_EEC4->bin(k).height() - _hist_EEC4->bin(nBins-(k+1)).height();
100        double ey4 = sqrt( pow(_hist_EEC4->bin(k).heightErr(),2) + pow(_hist_EEC4->bin(nBins-(k+1)).heightErr(),2) );
101        points4.push_back(Point2D(x,y4,ex,ey4));
102
103        double y5 = _hist_EEC5->bin(k).height() - _hist_EEC5->bin(nBins-(k+1)).height();
104        double ey5 = sqrt( pow(_hist_EEC5->bin(k).heightErr(),2) + pow(_hist_EEC5->bin(nBins-(k+1)).heightErr(),2) );
105        points5.push_back(Point2D(x,y5,ex,ey5));
106
107        double y6 = _hist_EEC6->bin(k).height() - _hist_EEC6->bin(nBins-(k+1)).height();
108        double ey6 = sqrt( pow(_hist_EEC6->bin(k).heightErr(),2) + pow(_hist_EEC6->bin(nBins-(k+1)).heightErr(),2) );
109        points6.push_back(Point2D(x,y6,ex,ey6));
110      }
111
112      _hist_AEEC1->addPoints(points1);
113      _hist_AEEC2->addPoints(points2);
114      _hist_AEEC3->addPoints(points3);
115      _hist_AEEC4->addPoints(points4);
116      _hist_AEEC5->addPoints(points5);
117      _hist_AEEC6->addPoints(points6);
118    }
119
120
121  private:
122
123    Histo1DPtr _hist_EEC1, _hist_EEC2, _hist_EEC3, _hist_EEC4, _hist_EEC5, _hist_EEC6;
124    Scatter2DPtr _hist_AEEC1, _hist_AEEC2, _hist_AEEC3, _hist_AEEC4, _hist_AEEC5, _hist_AEEC6;
125
126  };
127
128
129  // The hook for the plugin system
130  RIVET_DECLARE_PLUGIN(ATLAS_2017_I1609253);
131
132
133}