Rivet analyses

title: ATLAS_2018_I1698006

Z(vv)+gamma measurement at 13 TeV

Experiment: ATLAS (LHC)

Inspire ID: 1698006

Status: VALIDATED

Authors: - Jon Butterworth - Michail Sokratis - Yoran Yeh

References: - Expt page: ATLAS-STDM-2017-18 - JHEP 12 (2018) 010 - 10.1007/JHEP12(2018)010 - arXiv: 1810.04995

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - p + p -> Z0 nu nubar gamma at 13 TeV

The production of Z bosons in association with a high-energy photon (Z$\gamma$ production) is studied in the neutrino decay channel of the Z boson using pp collisions at $\sqrt s$ = 13 TeV. The analysis uses a data sample with an integrated luminosity of 36.1 fb-1 collected by the ATLAS detector at the LHC in 2015 and 2016. Candidate Z$\gamma$ events with invisible decays of the Z boson are selected by requiring significant transverse momentum (pT) of the dineutrino system in conjunction with a single isolated photon with large transverse energy (ET). The rate of Z$\gamma$ production is measured as a function of photon ET, dineutrino system pT and jet multiplicity. Evidence of anomalous triple gauge-boson couplings is sought in Z$\gamma$ production with photo ET greater than 600 GeV. No excess is observed relative to the Standard Model expectation, and upper limits are set on the strength of ZZ$\gamma$ and Z$\gamma\gamma$ couplings.

Source code:ATLAS_2018_I1698006.cc

```c++

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/InvisibleFinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// @brief ATLAS pTmiss+gamma measurement at 13 TeV class ATLAS_2018_I1698006 : public Analysis { public:

/// Default constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2018_I1698006);


/// @name Analysis methods
/// @{
void init() {

  // Get options
  // Default (OFF) uses the extended phase space of the paper.
  // LVETO ON will add an additonal lepton veto to reject non-Zgamma events
  // (for conservative BSM limits, for example).
  _mode = 0;
  if (getOption("LVETO") == "ON") _mode = 1;

  //prompt photons
  const Cut photoncut = Cuts::abspid == PID::PHOTON && Cuts::Et > 150 * GeV && Cuts::abseta < 2.37;
  const PromptFinalState photon_fs(photoncut);
  declare(photon_fs, "Photons");

  //missing energy (prompt neutrinos)
  declare(InvisibleFinalState(OnlyPrompt::YES), "MET");

  if (_mode == 1) {
    FinalState allLeps(Cuts::abspid == PID::ELECTRON || Cuts::abspid == PID::MUON);
    FinalState photons(Cuts::abspid == PID::PHOTON);
    PromptFinalState promptLeps(allLeps);
    Cut dressedLep_cuts = (Cuts::abseta < 2.7) && (Cuts::pT > 7 * GeV);
    LeptonFinder dressedLeps(promptLeps, photons, 0.1, dressedLep_cuts);
    declare(dressedLeps, "dressedLeptons");
  }

  //jets. run the jet finder on a final state without the prompt photons, and without neutrinos or muons
  VetoedFinalState jet_fs(Cuts::abseta > 4.5);
  jet_fs.addVetoOnThisFinalState(photon_fs);
  FastJets fastjets(jet_fs, JetAlg::ANTIKT, 0.4, JetMuons::NONE, JetInvisibles::NONE);
  declare(fastjets, "Jets");


  //books histograms
  //fig.4a
  book(_h["Et_inc"], 2, 1, 1);
  //fig.4b
  book(_h["Et_exc"], 3, 1, 1);
  //fig.5a
  book(_h["pT_inc"], 4, 1, 1);
  //fig.5b
  book(_h["pT_exc"], 5, 1, 1);
  //fig.6
  book(_h["Njets"], 6, 1, 1);
}


void analyze(const Event& event) {

  const Particles& photons = apply<PromptFinalState>(event, "Photons").particlesByPt();
  const Jets& jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 50 * GeV);
  const FinalState& metfs = apply<InvisibleFinalState>(event, "MET");
  Vector3 met_vec;
  for (const Particle& p : metfs.particles()) met_vec += p.mom().perpVec();


  if (_mode == 1) {
    const DressedLeptons& dressedLeptons = apply<LeptonFinder>(event, "dressedLeptons").dressedLeptons();
    if (dressedLeptons.size() > 0) vetoEvent;
  }

  //Nγ==1 and Emiss > 150 GeV
  if (met_vec.mod() > 150 * GeV && photons.size() == 1) {

    //inclusive case (Njet>=0)
    //if (jets.size()>=0){ //< size is always >= 0
    {
      bool dR_veto = any(jets, DeltaRLess(photons[0], 0.3));
      if (not dR_veto) {
        double Et_photon = photons[0].Et() / GeV;
        _h["Et_inc"]->fill(Et_photon);
        //fill in missing energy (neutrino) pT histogram (inclusive)
        _h["pT_inc"]->fill(met_vec.mod() / GeV);
      }
    }

    //exclusive case (Njet==0)
    if (jets.size() == 0) {
      double Et_photon = photons[0].Et() / GeV;
      _h["Et_exc"]->fill(Et_photon);
      //fill in missing energy (neutrino) pT histogram (exclusive)
      _h["pT_exc"]->fill(met_vec.mod() / GeV);
    }

    _h["Njets"]->fill(jets.size());
  }
}


void finalize() {
  const double sf = crossSection() / femtobarn / sumOfWeights();
  scale(_h, sf);
}

/// @}

private:

map<string, Histo1DPtr> _h;

size_t _mode;

};

RIVET_DECLARE_PLUGIN(ATLAS_2018_I1698006);

} ```