Rivet analyses

Measurement and QCD analysis of double-differential inclusive jet cross sections in pp collisions at $\sqrt{s} = 8$,TeV and cross-section ratios to 2.76 and 7 TeV

Experiment: CMS (LHC)

Inspire ID: 1487277

Status: VALIDATED

Authors: - Hannes Jung

References: - DOI:10.1007/JHEP03(2017)156 - arXiv: 1609.05331 - Expt page: CMS-SMP-14-001

Beams: p+ p+

Beam energies: (4000.0, 4000.0)GeV

Run details: - QCD at $\sqrt{s} = 8~\TeV$

A measurement of the double-differential inclusive jet cross section as a function of the jet transverse momentum p⟂ and the absolute jet rapidity |y| is presented. Data from LHC proton-proton collisions at $\sqrt{s}=8\TeV$, corresponding to an integrated luminosity of 19.7 fb^{-1}, have been collected with the CMS detector. Jets are reconstructed using the anti-$\kt$ clustering algorithm with a size parameter of 0.7 in a phase space region covering jet p⟂ from $74\GeV$ up to $2.5\TeV$ and jet absolute rapidity up to |y| = 3.0. The low-p⟂ jet range between 21 and $74\GeV$ is also studied up to |y| = 4.7, using a dedicated data sample corresponding to an integrated luminosity of 5.6. The measured jet cross section is corrected for detector effects and compared with the predictions from perturbative QCD at next-to-leading order (NLO) using various sets of parton distribution functions (PDF). Cross section ratios to the corresponding measurements performed at 2.76 and $7\TeV$ are presented. From the measured double-differential jet cross section, the value of the strong coupling constant evaluated at the Z mass is αS(MZ) = 0.1164−0.0043+0.0060, where the errors include the PDF, scale, nonperturbative effects and experimental uncertainties, using the CT10 NLO PDFs. Improved constraints on PDFs based on the inclusive jet cross section measurement are presented.

Source code:CMS_2016_I1487277.cc

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

namespace Rivet {

  // Inclusive jet pT
  class CMS_2016_I1487277 : public Analysis {
  public:

    // Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2016_I1487277);


    // Book histograms and initialize projections:
    void init() {
      const FinalState fs;

      // Initialize the projectors:
      declare(FastJets(fs, JetAlg::ANTIKT, 0.7),"Jets");

      // Book histograms:
      book(_hist_sigma, {0., 0.5, 1., 1.5, 2., 2.5, 3., 3.2, 4.7});
      for (auto& b : _hist_sigma->bins()) {
        if(b.index()<7)
          book(b, b.index(), 1, 1);
        else if(b.index()==8)
          book(b, 7, 1, 1);
      }

    }

    // Analysis
    void analyze(const Event &event) {
      const FastJets &fj = apply<FastJets>(event,"Jets");
      const Jets& jets = fj.jets(Cuts::ptIn(18*GeV, 5000.0*GeV) && Cuts::absrap < 5.2);

      // Fill the relevant histograms:
      for (const Jet &j : jets) {
        _hist_sigma->fill(j.absrap(), j.pT());
      }
    }

    // Finalize
    void finalize() {
      scale(_hist_sigma, crossSection()/picobarn/sumOfWeights()/2.0);
      _hist_sigma->divByGroupWidth();
    }

  private:

    Histo1DGroupPtr _hist_sigma;

  };

  RIVET_DECLARE_PLUGIN(CMS_2016_I1487277);

}