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 |η| < 2 and transverse momentum pT > 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 pT for leading track jet pT-leading  > 3~GeV and pT-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 pT, and three distributions for the two previous quantities as well as pT for all the particles in the transverse region.

Source code:CMS_2011_I916908.cc

// -*- C++ -*-

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