Rivet analyses

title: LHCB_2014_I1262703

Study of forward Z + jet production in $pp$ collisions at $\sqrt{s}=7$ TeV in the LHCb fiducial phase-space

Experiment: LHCb (LHC)

Inspire ID: 1262703

Status: VALIDATED

Authors: - William Barter - Albert Bursche - Marek Sirendi

References: - J. High Energy Phys.1401:033,2014 - DOI: 10.1007/jhep01(2014)033 - arXiv: 1310.8197

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - $pp$ $Z +$ jet events at 7 TeV with direct $\mu$ decays

A study of forward $Z +$ jet production in $pp$ collisions at $\sqrt{s}=7$ TeV is presented. Results are shown for two jet thresholds of $p_T>10$ GeV and $p_T>20$ GeV. Total cross-sections and six differential cross-sections are measured.

Source code:LHCB_2014_I1262703.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FastJets.hh"

namespace Rivet {

/// @brief Study of forward Z + jet production at 7 TeV at LHCb /// /// @author W. Barter, A. Bursche, M. Sirendi (Rivet implementation) class LHCB_2014_I1262703 : public Analysis { public:

/// Default constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2014_I1262703);


/// Initialise histograms and projections
void init() {

  // Projections
  const Cut mycut = Cuts::eta >= 2.0 && Cuts::eta <= 4.5 && Cuts::pT > 20 * GeV;
  DileptonFinder zfinder(91.2 * GeV, 0.0, mycut && Cuts::abspid == PID::MUON,
                         Cuts::massIn(60 * GeV, 120 * GeV));
  declare(zfinder, "DileptonFinder");
  FastJets jetpro(zfinder.remainingFinalState(), JetAlg::ANTIKT, 0.5);
  declare(jetpro, "Jets");

  // Histograms
  book(_h_jet_pT, 3, 1, 1);
  book(_h_jet_eta20, 4, 1, 1);
  book(_h_jet_eta10, 4, 1, 2);
  book(_h_Z_y20, 5, 1, 1);
  book(_h_Z_y10, 5, 1, 2);
  book(_h_Z_pT20, 6, 1, 1);
  book(_h_Z_pT10, 6, 1, 2);
  book(_h_dphi20, 7, 1, 1);
  book(_h_dphi10, 7, 1, 2);
  book(_h_dy20, 8, 1, 1);
  book(_h_dy10, 8, 1, 2);
}


/// Do the analysis
void analyze(const Event& e) {

  const DileptonFinder& zfinder = apply<DileptonFinder>(e, "DileptonFinder");
  if (zfinder.bosons().size() != 1) vetoEvent;
  const Particles leptons = zfinder.constituents();

  const Cut jetSelector = Cuts::eta >= 2.0 && Cuts::eta <= 4.5 && Cuts::pT > 10 * GeV;
  const Jets jets = apply<FastJets>(e, "Jets").jetsByPt(jetSelector);

  if (jets.empty()) vetoEvent;

  // Clean the jets against the lepton candidates with a deltaR cut of 0.4
  const Jets cleanedJets = discard(jets, [&](const Jet& j) { return any(leptons, deltaRLess(j, 0.4)); });
  // vector<const Jet*> cleanedJets;
  // for (size_t i = 0; i < jets.size(); i++) {
  //   bool isolated = true;
  //   for (size_t j = 0; j < 2; j++) {
  //     if (deltaR(leptons[j], jets[i]) < 0.4) {
  //       isolated = false;
  //       break;
  //     }
  //   }
  //   if (isolated) cleanedJets.push_back(&jets[i]);
  // }

  // Require at least 1 survivor and note if it is above a 20 GeV jet pT threshold
  if (cleanedJets.empty()) vetoEvent;
  const bool above20 = cleanedJets[0].pT() > 20 * GeV;
  const double dphi = deltaPhi(zfinder.boson(), cleanedJets[0]);
  const double drap = zfinder.boson().rap() - cleanedJets[0].rap();

  // Fill histograms
  _h_jet_pT->fill(cleanedJets[0].pT() / GeV);
  _h_jet_eta10->fill(cleanedJets[0].eta());
  _h_Z_y10->fill(zfinder.boson().rap());
  _h_Z_pT10->fill(zfinder.boson().pT() / GeV);
  _h_dphi10->fill(dphi);
  _h_dy10->fill(drap);
  if (above20) {
    _h_jet_eta20->fill(cleanedJets[0].eta());
    _h_Z_y20->fill(zfinder.boson().rap());
    _h_Z_pT20->fill(zfinder.boson().pT() / GeV);
    _h_dphi20->fill(dphi);
    _h_dy20->fill(drap);
  }
}


/// Finalize
void finalize() {
  normalize(_h_jet_pT);
  normalize(_h_jet_eta20);
  normalize(_h_jet_eta10);
  normalize(_h_Z_y20);
  normalize(_h_Z_y10);
  normalize(_h_Z_pT20);
  normalize(_h_Z_pT10);
  normalize(_h_dphi20);
  normalize(_h_dphi10);
  normalize(_h_dy20);
  normalize(_h_dy10);
}


/// Histograms
Histo1DPtr _h_jet_pT, _h_jet_eta20, _h_jet_eta10, _h_Z_y20, _h_Z_y10, _h_Z_pT20, _h_Z_pT10, _h_dphi20,
    _h_dphi10, _h_dy20, _h_dy10;

};

RIVET_DECLARE_PLUGIN(LHCB_2014_I1262703);

} ```