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CMS_2018_I1643640

Azimuthal correlations for inclusive 2-jet, 3-jet, and 4-jet events in pp collisions at $\sqrt{s}$ = 13 TeV
Experiment: CMS (LHC)
Inspire ID: 1643640
Status: VALIDATED
Authors:
  • cms-pag-conveners-smp@cern.ch
  • Hannes Jung
  • Paolo Gunnellini
  • Panos Kokkas
References:
  • 10.1140/epjc/s10052-018-6033-4
  • arxiv:1712.05471
  • Public page: CMS-SMP-16-014
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • QCD at $\sqrt{s} = 13 \text{TeV}$

Azimuthal correlations between the two jets with the largest transverse momenta $p_T$ in inclusive 2-, 3-, and 4-jet events are presented for several regions of the leading jet $p_T$ up to 4 TeV. For 3- and 4-jet scenarios, measurements of the minimum azimuthal angles between any two of the three or four leading $p_T$ jets are also presented. The analysis is based on data from proton-proton collisions collected by the CMS Collaboration at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Calculations based on leading-order matrix elements supplemented with parton showering and hadronization do not fully describe the data, so next-to-leading-order calculations matched with parton shower and hadronization models are needed to better describe the measured distributions. Furthermore, we show that azimuthal jet correlations are sensitive to details of the parton showering, hadronization, and multiparton interactions. A next-to-leading-order calculation matched with parton showers in the MC\@NLO method, as implemented in HERWIG 7, gives a better overall description of the measurements than the POWHEG method.

Source code: CMS_2018_I1643640.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  /// CMS Azimuthal corellations at 13 TeV
 10  class CMS_2018_I1643640 : public Analysis {
 11  public:
 12
 13    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2018_I1643640);
 14
 15    void init() {
 16      FinalState fs;
 17      FastJets akt(fs, JetAlg::ANTIKT, 0.4);
 18      declare(akt, "antikT");
 19
 20      const vector<double> edges_2J{200., 300., 400., 500., 600., 700., 800., 1000., 1200., 7000.};
 21      const vector<double> edges{200., 300., 400., 500., 600., 700., 800., 1000., 7000.};
 22      book(_h_deltaPhi_2J_phi12, edges_2J);
 23      book(_h_deltaPhi_3J_phi12, edges);
 24      book(_h_deltaPhi_4J_phi12, edges);
 25      book(_h_deltaPhi_3J_phimin2J, edges);
 26      book(_h_deltaPhi_4J_phimin2J, edges);
 27      for (size_t i=1; i<_h_deltaPhi_2J_phi12->numBins()+1; ++i) {
 28        book(_h_deltaPhi_2J_phi12->bin(i), i, 1, 1);
 29        if (i==9)  continue;
 30        book(_h_deltaPhi_3J_phi12->bin(i), 9+i, 1, 1);
 31        book(_h_deltaPhi_4J_phi12->bin(i), 17+i, 1, 1);
 32        book(_h_deltaPhi_3J_phimin2J->bin(i), 25+i, 1, 1);
 33        book(_h_deltaPhi_4J_phimin2J->bin(i), 33+i, 1, 1);
 34      }
 35    }
 36
 37
 38    void analyze(const Event & event) {
 39      const Jets& jets = apply<JetFinder>(event, "antikT").jetsByPt();
 40
 41      // 2 jet case and Delta_phi12
 42      if( jets.size() >= 2 ) {
 43        if ( (jets[0].pT() >= 200.*GeV)  &&  (jets[1].pT() >= 100.*GeV) ) {
 44          if ( (fabs(jets[0].rap()) <= 2.5)  &&  (fabs(jets[1].rap()) <= 2.5) ) {
 45            double dphi = deltaPhi(jets[0].phi(), jets[1].phi());
 46            _h_deltaPhi_2J_phi12->fill(jets[0].pT(), dphi);
 47          }
 48        }
 49      }
 50
 51      // 3 jet case and Delta_phi12
 52      if ( jets.size() >= 3 ) {
 53        if ( (jets[0].pT() >= 200.*GeV)  &&  (jets[1].pT() >= 100.*GeV)  && (jets[2].pT() >= 100.*GeV) ) {
 54          if ( (fabs(jets[0].rap()) <= 2.5)  &&  (fabs(jets[1].rap()) <= 2.5) &&  (fabs(jets[2].rap()) <= 2.5)) {
 55            double dphi = deltaPhi(jets[0].phi(), jets[1].phi());
 56            _h_deltaPhi_3J_phi12->fill(jets[0].pT(), dphi);
 57          }
 58        }
 59      }
 60
 61      // 4 jet case and Delta_phi12
 62      if ( jets.size() >= 4 ) {
 63        if ( (jets[0].pT() >= 200.*GeV)  &&  (jets[1].pT() >= 100.*GeV)  && (jets[2].pT() >= 100.*GeV)   && (jets[3].pT() >= 100.*GeV)) {
 64          if ( (fabs(jets[0].rap()) <= 2.5)  &&  (fabs(jets[1].rap()) <= 2.5) &&  (fabs(jets[2].rap()) <= 2.5) &&  (fabs(jets[3].rap()) <= 2.5)) {
 65            double dphi = deltaPhi(jets[0].phi(), jets[1].phi());
 66            _h_deltaPhi_4J_phi12->fill(jets[0].pT(), dphi);
 67          }
 68        }
 69      }
 70
 71      // 3 jet case and Delta_Phi_min2j
 72      if ( jets.size() >= 3 ) {
 73        if ( (jets[0].pT() >= 200.*GeV)  &&  (jets[1].pT() >= 100.*GeV)  && (jets[2].pT() >= 100.*GeV) ) {
 74          if ( (fabs(jets[0].rap()) <= 2.5)  &&  (fabs(jets[1].rap()) <= 2.5) &&  (fabs(jets[2].rap()) <= 2.5)) {
 75            double dphi01 = deltaPhi(jets[0].phi(), jets[1].phi());
 76            if (dphi01 >= PI/2. ){
 77              double dphi02 = deltaPhi(jets[0].phi(), jets[2].phi());
 78              double dphi12 = deltaPhi(jets[1].phi(), jets[2].phi());
 79              // evaluate DPhi2Jmin
 80              vector<double> Dphis2J{dphi01,dphi02,dphi12};
 81              double DPhi2Jmin = min(Dphis2J);
 82              // double Dphis2J[3] = {dphi01,dphi02,dphi12};
 83              // double DPhi2Jmin = Dphis2J[0];
 84              // for (int gg=1; gg<3; ++gg) { if (DPhi2Jmin>Dphis2J[gg]) DPhi2Jmin = Dphis2J[gg]; }
 85              _h_deltaPhi_3J_phimin2J->fill(jets[0].pT(), DPhi2Jmin);
 86            }
 87          }
 88        }
 89      }
 90
 91      // 4 jet case and Delta_Phi_min2j
 92      if ( jets.size() >= 4 ) {
 93        if ( (jets[0].pT() >= 200.*GeV)  &&  (jets[1].pT() >= 100.*GeV)  && (jets[2].pT() >= 100.*GeV)   && (jets[3].pT() >= 100.*GeV)) {
 94          if ( (fabs(jets[0].rap()) <= 2.5)  &&  (fabs(jets[1].rap()) <= 2.5) &&  (fabs(jets[2].rap()) <= 2.5) &&  (fabs(jets[3].rap()) <= 2.5)) {
 95            double dphi01 = deltaPhi(jets[0].phi(), jets[1].phi());
 96            if (dphi01 >= PI/2.) {
 97              double dphi02 = deltaPhi(jets[0].phi(), jets[2].phi());
 98              double dphi03 = deltaPhi(jets[0].phi(), jets[3].phi());
 99              double dphi12 = deltaPhi(jets[1].phi(), jets[2].phi());
100              double dphi13 = deltaPhi(jets[1].phi(), jets[3].phi());
101              double dphi23 = deltaPhi(jets[2].phi(), jets[3].phi());
102              /// evaluate DPhi2Jmin
103              // double Dphis2J[6]={dphi01,dphi02,dphi03,dphi12,dphi13,dphi23};
104              // double DPhi2Jmin=Dphis2J[0];
105              // for(int gg=1; gg<6; ++gg){ if(DPhi2Jmin>Dphis2J[gg]){DPhi2Jmin=Dphis2J[gg];} }
106              vector<double> Dphis2J{dphi01,dphi02,dphi03,dphi12,dphi13,dphi23};
107              double DPhi2Jmin = min(Dphis2J);
108              _h_deltaPhi_4J_phimin2J->fill(jets[0].pT(), DPhi2Jmin);
109            }
110          }
111        }
112      }
113    }  // end analyze
114
115
116    void finalize() {
117      normalize(_h_deltaPhi_2J_phi12);
118      normalize(_h_deltaPhi_3J_phi12);
119      normalize(_h_deltaPhi_4J_phi12);
120      normalize(_h_deltaPhi_3J_phimin2J);
121      normalize(_h_deltaPhi_4J_phimin2J);
122    }
123
124
125  private:
126
127    Histo1DGroupPtr _h_deltaPhi_2J_phi12;
128    Histo1DGroupPtr _h_deltaPhi_3J_phi12;
129    Histo1DGroupPtr _h_deltaPhi_4J_phi12;
130    Histo1DGroupPtr _h_deltaPhi_3J_phimin2J;
131    Histo1DGroupPtr _h_deltaPhi_4J_phimin2J;
132
133  };
134
135
136  RIVET_DECLARE_PLUGIN(CMS_2018_I1643640);
137
138}