Rivet analyses

title: ATLAS_2011_I891834

Calo-based underlying event at 900 GeV and 7 TeV in ATLAS

Experiment: ATLAS (LHC)

Inspire ID: 891834

Status: VALIDATED

Authors: - Jinlong Zhang - Andy Buckley

References: - Expt page: ATLAS-STDM-2010-05 - arXiv: 1103.1816

Beams: p+ p+

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

Run details: - pp QCD interactions at 900 GeV and 7 TeV. Diffractive events should be included, but only influence the lowest bins. Multiple kinematic cuts should not be required.

Underlying event measurements with the ATLAS detector at the LHC at center-of-mass energies of 900 GeV and 7 TeV, using calorimeter clusters rather than charged tracks.

Source code:ATLAS_2011_I891834.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Calo-based underlying event at 900 GeV and 7 TeV in ATLAS /// /// @author Jinlong Zhang class ATLAS_2011_I891834 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2011_I891834);


void init() {
  const FinalState fs500(Cuts::abseta < 2.5 && Cuts::pT >= 500 * MeV);
  declare(fs500, "FS500");
  const FinalState fslead(Cuts::abseta < 2.5 && Cuts::pT >= 1.0 * GeV);
  declare(fslead, "FSlead");

  for (double eVal : allowedEnergies()) {

    const string en = toString(round(eVal));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    bool is7TeV(en == "7000");

    // N profiles, 500 MeV pT cut
    book(_h[en + "N_transverse"], 1 + is7TeV, 1, 1);
    // pTsum profiles, 500 MeV pT cut
    book(_h[en + "ptsum_transverse"], 3 + is7TeV, 1, 1);
    // N vs. Delta(phi) profiles, 500 MeV pT cut
    book(_h[en + "N_vs_dPhi_1"], 13 + is7TeV, 1, 1);
    book(_h[en + "N_vs_dPhi_2"], 13 + is7TeV, 1, 2);
    book(_h[en + "N_vs_dPhi_3"], 13 + is7TeV, 1, 3);
  }
  raiseBeamErrorIf(_sqs.empty());
}


void analyze(const Event& event) {
  // Require at least one cluster in the event with pT >= 1 GeV
  const FinalState& fslead = apply<FinalState>(event, "FSlead");
  if (fslead.size() < 1) vetoEvent;

  // These are the particles  with pT > 500 MeV
  const FinalState& chargedNeutral500 = apply<FinalState>(event, "FS500");

  // Identify leading object and its phi and pT
  Particles particles500 = chargedNeutral500.particlesByPt();
  Particle p_lead = particles500[0];
  const double philead = p_lead.phi();
  const double etalead = p_lead.eta();
  const double pTlead = p_lead.pT();
  MSG_DEBUG("Leading object: pT = " << pTlead << ", eta = " << etalead << ", phi = " << philead);

  // Iterate over all > 500 MeV particles and count particles and scalar pTsum in the three regions
  vector<double> num500(3, 0), ptSum500(3, 0.0);
  // Temporary histos that bin N in dPhi.
  // NB. Only one of each needed since binnings are the same for the energies and pT cuts
  YODA::Histo1D htemp(_h[_sqs + "N_vs_dPhi_1"]->xEdges(), "tmp");
  for (const Particle& p : particles500) {
    const double pT = p.pT();
    const double dPhi = deltaPhi(philead, p.phi());
    const int ir = region_index(dPhi);
    num500[ir] += 1;
    ptSum500[ir] += pT;

    // Fill temp histos to bin N in dPhi
    if (p.genParticle()
        != p_lead.genParticle()) { // We don't want to fill all those zeros from the leading track...
      htemp.fill(dPhi);
    }
  }


  // Now fill underlying event histograms
  // The densities are calculated by dividing the UE properties by dEta*dPhi
  // -- each region has a dPhi of 2*PI/3 and dEta is two times 2.5
  const double dEtadPhi = (2 * 2.5 * 2 * PI / 3.0);
  _h[_sqs + "N_transverse"]->fill(pTlead / GeV, num500[1] / dEtadPhi);
  _h[_sqs + "ptsum_transverse"]->fill(pTlead / GeV, ptSum500[1] / GeV / dEtadPhi);

  // Update the "proper" dphi profile histograms
  // Note that we fill dN/dEtadPhi: dEta = 2*2.5, dPhi = 2*PI/nBins
  // The values tabulated in the note are for an (undefined) signed Delta(phi) rather than
  // |Delta(phi)| and so differ by a factor of 2: we have to actually norm for angular range = 2pi
  for (const auto& b : htemp.bins()) {
    double mean = b.xMid(), value = 0.;
    if (b.numEntries() > 0) {
      mean = b.xMean();
      value = b.sumW() / b.xWidth() / 10.0;
    }
    if (pTlead / GeV >= 1.0) _h[_sqs + "N_vs_dPhi_1"]->fill(mean, value);
    if (pTlead / GeV >= 2.0) _h[_sqs + "N_vs_dPhi_2"]->fill(mean, value);
    if (pTlead / GeV >= 3.0) _h[_sqs + "N_vs_dPhi_3"]->fill(mean, value);
  }
}


// Little helper function to identify Delta(phi) regions
inline int region_index(double dphi) {
  assert(inRange(dphi, 0.0, PI, CLOSED, CLOSED));
  if (dphi < PI / 3.0) return 0;
  if (dphi < 2 * PI / 3.0) return 1;
  return 2;
}

private:

string _sqs = "";

map<string, Profile1DPtr> _h;

};

RIVET_DECLARE_ALIASED_PLUGIN(ATLAS_2011_I891834, ATLAS_2011_S8994773);

} ```

Aliases: - ATLAS_2011_S8994773