Rivet analyses

Measurement of ratio of the 3-jet over 2-jet cross section in pp collisions at $\sqrt{s} = 7$ TeV

Experiment: CMS (LHC)

Inspire ID: 912560

Status: VALIDATED

Authors: - Tomo Umer

References: - Phys. Lett. B 702 (2011) 336

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - Inclusive QCD at 7 TeV. $\hat{\pT}$ (or equivalent) greater than 30 GeV

A measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum, HT, in the range 0.2 < HT < 2.5 TeV is presented. The data have been collected at a proton–proton centre-of-mass energy of 7~TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36/pb. Jets are anti-kt with R = 0.5, $p_\perp > 50~\GeV$ and |η| < 2.5.

Source code:CMS_2011_I912560.cc

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

namespace Rivet {


  /// CMS ratio of 3-jet to 2-jet cross-sections
  class CMS_2011_I912560 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I912560);


    void init() {
      FinalState fs;
      FastJets akt(fs, JetAlg::ANTIKT, 0.5);
      declare(akt, "antikT");

      book(_h_tmp_dijet, "TMP/dijet", refData(1, 1, 1));
      book(_h_tmp_trijet, "TMP/trijet", refData(1, 1, 1));
      book(_h_r32, 1, 1, 1);
    }


    void analyze(const Event& event) {

      Jets highpT_jets;
      double HT = 0;
      for (const Jet& jet : apply<JetFinder>(event, "antikT").jetsByPt(Cuts::pT > 50.0 * GeV)) {
        if (jet.abseta() < 2.5) {
          highpT_jets.push_back(jet);
          HT += jet.pT();
        }
      }
      if (highpT_jets.size() < 2) vetoEvent;
      if (highpT_jets.size() >= 2) _h_tmp_dijet->fill(HT / TeV);
      if (highpT_jets.size() >= 3) _h_tmp_trijet->fill(HT / TeV);
    }


    void finalize() {
      divide(_h_tmp_trijet, _h_tmp_dijet, _h_r32);
    }


  private:

    /// @{
    Histo1DPtr _h_tmp_dijet, _h_tmp_trijet;
    Estimate1DPtr _h_r32;
    /// @}
  };


  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_I912560, CMS_2011_S9088458);

}

Aliases: - CMS_2011_S9088458