Rivet analyses

Traditional leading jet UE measurement at $\sqrt{s} = 0.9$ and 7 TeV

Experiment: CMS (LHC)

Inspire ID: 916908

Status: VALIDATED

Authors: - Mohammed Zakaria

References: - J. High Energy Phys 09 (2011) 109

Beams: p+ p+

Beam energies: (450.0, 450.0); (3500.0, 3500.0)GeV

Run details: - Requires inclusive inelastic events (non-diffractive and inelastic diffractive). The profile plots require large statistics.

A measurement of the underlying activity in scattering processes with a hard scale in the several-GeV region is performed in proton-proton collisions at Energies of 0.9 and 7~TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity $|\eta| < 2$ and transverse momentum $p_\text{T} > 0.5$~GeV/$c$ is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. Various comparisons are made between the two different energies and also beteen two sets of cuts on $p_\text{T}$ for leading track jet $p_\text{T}$-leading $> 3$~GeV and $p_\text{T}$-leading $> 20$~GeV. The activity is studied using 5 types of plots. Two profile plots for the multiplicity of charged particles and the scalar sum of $p_\text{T}$, and three distributions for the two previous quantities as well as $p_\text{T}$ for all the particles in the transverse region.

Source code:CMS_2011_I916908.cc

// -*- C++ -*-

#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"

namespace Rivet {


  /// UE charged particles vs. leading jet
  class CMS_2011_I916908 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I916908);


    void init() {
      const ChargedFinalState cfs(Cuts::abseta < 2.0 && Cuts::pT >= 500 * MeV);
      declare(cfs, "CFS");

      const ChargedFinalState cfsforjet(Cuts::abseta < 2.5 && Cuts::pT >= 500 * MeV);
      const FastJets jetpro(cfsforjet, JetAlg::SISCONE, 0.5);
      declare(jetpro, "Jets");

      for (double eVal : allowedEnergies()) {
        const string en = toString(round(eVal));
        if (isCompatibleWithSqrtS(eVal)) _sqs = en;

        if (en == "7000"s) {
          book(_p[en + "Nch_vs_pT"], 1, 1, 1); // Nch vs. pT_max
          book(_p[en + "Sum_vs_pT"], 2, 1, 1); // sum(pT) vs. pT_max
          book(_h[en + "pT3_Nch"], 5, 1, 1);   // transverse Nch,     pT_max > 3GeV
          book(_h[en + "pT3_Sum"], 6, 1, 1);   // transverse sum(pT), pT_max > 3GeV
          book(_h[en + "pT3_pT"], 7, 1, 1);    // transverse pT,      pT_max > 3GeV
          book(_h[en + "pT20_Nch"], 8, 1, 1);  // transverse Nch,     pT_max > 20GeV
          book(_h[en + "pT20_Sum"], 9, 1, 1);  // transverse sum(pT), pT_max > 20GeV
          book(_h[en + "pT20_pT"], 10, 1, 1);  // transverse pT,      pT_max > 20GeV
        }
        else if (en == "900"s) {
          book(_p[en + "Nch_vs_pT"], 3, 1, 1); // Nch vs. pT_max
          book(_p[en + "Sum_vs_pT"], 4, 1, 1); // sum(pT) vs. pT_max
          book(_h[en + "pT3_Nch"], 11, 1, 1);  // transverse Nch,     pT_max > 3GeV
          book(_h[en + "pT3_Sum"], 12, 1, 1);  // transverse sum(pT), pT_max > 3GeV
          book(_h[en + "pT3_pT"], 13, 1, 1);   // transverse pT,      pT_max > 3GeV
        }
        book(_c[en + "pT3"], "TMP/nch_tot_pT3" + en);
        book(_c[en + "pT20"], "TMP/nch_tot_pT20" + en);
      }
      raiseBeamErrorIf(_sqs.empty());
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // Find the lead jet, applying a restriction that the jets must be within |eta| < 2.
      FourMomentum p_lead;
      for (const Jet& j :
           apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 1.0 * GeV && Cuts::abseta < 2.0)) {
        p_lead = j.momentum();
        break;
      }
      if (p_lead.isZero()) vetoEvent;
      const double philead = p_lead.phi();
      const double pTlead = p_lead.pT();

      Particles particles = apply<ChargedFinalState>(event, "CFS").particlesByPt();

      int nTransverse = 0;
      double ptSumTransverse = 0.;
      for (const Particle& p : particles) {
        double dphi = deltaPhi(philead, p.phi());
        if (dphi > PI / 3. && dphi < PI * 2. / 3.) { // Transverse region
          ++nTransverse;

          const double pT = p.pT() / GeV;
          ptSumTransverse += pT;

          if (pTlead > 3 * GeV) _h[_sqs + "pT3_pT"]->fill(pT / GeV);
          if (_sqs == "7000"s && pTlead > 20 * GeV) _h[_sqs + "pT20_pT"]->fill(pT / GeV);
        }
      }

      const double area = 8. / 3. * PI;
      _p[_sqs + "Nch_vs_pT"]->fill(pTlead / GeV, 1. / area * nTransverse);
      _p[_sqs + "Sum_vs_pT"]->fill(pTlead / GeV, 1. / area * ptSumTransverse);
      if (pTlead > 3.0 * GeV) {
        _h[_sqs + "pT3_Nch"]->fill(nTransverse);
        _h[_sqs + "pT3_Sum"]->fill(ptSumTransverse / GeV);
        _c[_sqs + "pT3"]->fill(nTransverse);
      }
      if (_sqs == "7000"s && pTlead > 20 * GeV) {
        _h[_sqs + "pT20_Nch"]->fill(nTransverse);
        _h[_sqs + "pT20_Sum"]->fill(ptSumTransverse / GeV);
        _c[_sqs + "pT20"]->fill(nTransverse);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      for (double eVal : allowedEnergies()) {
        const string en = toString(round(eVal));
        if (_h[en + "pT3_pT"]->sumW()) {
          normalize(_h[en + "pT3_pT"], dbl(*_c[en + "pT3"]) / _h[en + "pT3_Nch"]->sumW());
        }
        if (en == "7000"s && _h[en + "pT20_pT"]->sumW()) {
          normalize(_h[en + "pT20_pT"], dbl(*_c[en + "pT20"]) / _h[en + "pT20_Nch"]->sumW());
        }
      }
      for (auto& item : _h) {
        if (item.first.find("_pT") != string::npos) continue;
        normalize(item.second);
      }
    }


  private:

    /// @{
    map<string, CounterPtr> _c;
    map<string, Profile1DPtr> _p;
    map<string, Histo1DPtr> _h;

    string _sqs = "";
    /// @}
  };


  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_I916908, CMS_2011_S9120041);

}

Aliases: - CMS_2011_S9120041