Rivet analyses

Measurements of jet multiplicity and jet transverse momentum in multijet events in proton-proton collisions at = 13 TeV

Experiment: CMS (LHC)

Inspire ID: 2170533

Status: VALIDATED

Authors: - cms-pag-conveners-smp@cern.ch - Luis Ignacio Estevez Banos

References: - arXiv: 2210.13557 - Expt page: CMS-SMP-21-006 - Submitted to EPJC

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - pp to jets at $\sqrt{s}=13$ TeV. Data collected by CMS during the year 2016.

Multijet events at large transverse momentum (pT) are measured at $\sqrt{s}$ = 13 TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3 fb-1. The multiplicity of jets with pT > 50 GeV that are produced in association with a high-pT dijet system is measured in various ranges of the pT of the jet with the highest transverse momentum and as a function of the azimuthal angle difference between the two highest pT jets in the dijet system. The differential production cross sections are measured as a function of the transverse momenta of the four highest pT jets. The measurements are compared with leading and next-to-leading order matrix element calculations supplemented with simulations of parton shower, hadronization, and multiparton interactions. In addition, the measurements are compared with next-to-leading order matrix element calculations combined with transverse-momentum dependent parton densities and transverse-momentum dependent parton shower.

Source code:CMS_2022_I2170533.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {

  /// @brief Multijet events at 13 TeV
  class CMS_2022_I2170533 : public Analysis {

  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2022_I2170533);

    /// @name Analysis methods
    ///@{

    /// Book histograms and initialise projections before the run
    void init() {
      FinalState fs;
      FastJets akt(fs, JetAlg::ANTIKT, 0.4);
      declare(akt, "antikT");

      vector<double> edges = {0., 150., 170., 180.};
      book(_h_Mult_ptmax200, edges);
      book(_h_Mult_ptmax400, edges);
      book(_h_Mult_ptmax800, edges);
      for (size_t i = 0; i < _h_Mult_ptmax200->numBins(); ++i) {
        book(_h_Mult_ptmax200->bin(i + 1), i + 1, 1, 1);
        book(_h_Mult_ptmax400->bin(i + 1), i + 4, 1, 1);
        book(_h_Mult_ptmax800->bin(i + 1), i + 7, 1, 1);
      }

      // Pt of the first 4 jets
      book(_h_pT1_n1, 10, 1, 1);
      book(_h_pT2_n2, 11, 1, 1);
      book(_h_pT3_n3, 12, 1, 1);
      book(_h_pT4_n4, 13, 1, 1);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Preselection cuts for the jets
      const Jets& jets = apply<FastJets>(event, "antikT")
                             .jetsByPt(Cuts::pT > 20 * GeV
                                       && Cuts::absrap
                                           < 3.2); // rapidity and pt preselection |y| < 3.2 pT > 20 GeV

      int njet = 0; // jet counting

      // cuts after preselection
      if (jets.size() < 2) vetoEvent;                                // dijet cut
      if ((jets[0].pT() < 200.) or (jets[1].pT() < 100.)) vetoEvent; // pt cut on 2 leading jets
      if ((fabs(jets[0].rap()) > 2.5) or (fabs(jets[1].rap()) > 2.5))
        vetoEvent; // |y| < 2.5 cut on leading jets

      double dphi = deltaPhi(jets[0].phi(), jets[1].phi()) / degree;

      for (const Jet& j : jets) {
        if (j.pT() > 50. && fabs(j.rap()) < 2.5) njet = njet + 1; // Cuts on the extrajets
      }

      if (njet > 7) njet = 7; // Last bin in Multiplicity is inclusive

      if (jets[0].pT() > 200 && jets[0].pT() <= 400) _h_Mult_ptmax200->fill(dphi, njet);
      if (jets[0].pT() > 400 && jets[0].pT() <= 800) _h_Mult_ptmax400->fill(dphi, njet);
      if (jets[0].pT() > 800) _h_Mult_ptmax800->fill(dphi, njet);

      // Filling dijet 1,2 pT (The events are already selected with leadin jetpT > 200 GeV and 2nd jet pT > 100 GeV)
      _h_pT1_n1->fill(jets[0].pT());
      _h_pT2_n2->fill(jets[1].pT());

      // Filling extra jets pT (jet3 and jet4)
      if (njet > 2) _h_pT3_n3->fill(jets[2].pT());
      if (njet > 3) _h_pT4_n4->fill(jets[3].pT());
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      const double sf = crossSection() / picobarn / sumW();
      scale(_h_Mult_ptmax200, sf);
      scale(_h_Mult_ptmax400, sf);
      scale(_h_Mult_ptmax800, sf);
      scale({_h_pT1_n1, _h_pT2_n2, _h_pT3_n3, _h_pT4_n4}, sf);
    }

    ///@}

    /// @name Histograms
    ///@{

    Histo1DGroupPtr _h_Mult_ptmax200, _h_Mult_ptmax400, _h_Mult_ptmax800;
    Histo1DPtr _h_pT1_n1, _h_pT2_n2, _h_pT3_n3, _h_pT4_n4;

    ///@}
  };

  RIVET_DECLARE_PLUGIN(CMS_2022_I2170533);

} // namespace Rivet