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CMS_2011_S8950903

Dijet azimuthal decorrelations in $pp$ collisions at $\sqrt{s} = 7$ TeV
Experiment: CMS (LHC)
Inspire ID: 885663
Status: VALIDATED
Authors:
  • Tomo Umer
References:
  • Phys. Rev. Lett. 106 (2011) 122003
  • arXiv: 1101.5029
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Inclusive QCD at $\sqrt{s} = 7\;\text{TeV}$, $\hat{p_\perp} (or equivalent) greater than 20 GeV

Measurements of dijet azimuthal decorrelations in $pp$ collisions at $\sqrt{s} = 7$ TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9/pb. Jets are anti-$k_t$ with $R = 0.5$, $p_\perp > 80 (30)$ GeV and $|\eta| < 1.1$.

Source code: CMS_2011_S8950903.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"

namespace Rivet {

  // CMS azimuthal decorrelations
  class CMS_2011_S8950903 : public Analysis {
  public:

    CMS_2011_S8950903() : Analysis("CMS_2011_S8950903") {}


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

      _h_deltaPhi.addHistogram( 80.,  110., bookHisto1D(1, 1, 1));
      _h_deltaPhi.addHistogram(110.,  140., bookHisto1D(2, 1, 1));
      _h_deltaPhi.addHistogram(140.,  200., bookHisto1D(3, 1, 1));
      _h_deltaPhi.addHistogram(200.,  300., bookHisto1D(4, 1, 1));
      _h_deltaPhi.addHistogram(300., 7000., bookHisto1D(5, 1, 1));
    }


    void analyze(const Event & event) {
      const double weight = event.weight();

      const Jets& jets = apply<JetAlg>(event, "antikT").jetsByPt();
      if (jets.size() < 2) vetoEvent;

      if (fabs(jets[0].eta()) > 1.1 || jets[0].pT() < 80.) vetoEvent;
      if (fabs(jets[1].eta()) > 1.1 || jets[1].pT() < 30.) vetoEvent;

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

      _h_deltaPhi.fill(jets[0].pT(), dphi, weight);
    }


    void finalize() {
      foreach (Histo1DPtr histo, _h_deltaPhi.getHistograms()) {
        normalize(histo, 1.);
      }
    }

  private:

    BinnedHistogram<double> _h_deltaPhi;

  };

  // This global object acts as a hook for the plugin system
  DECLARE_RIVET_PLUGIN(CMS_2011_S8950903);

}