Rivet analyses

title: ATLAS_2022_I2077570

Z + high transverse momentum jets at ATLAS

Experiment: ATLAS (LHC)

Inspire ID: 2077570

Status: VALIDATED

Authors: - Alexandre Laurier

References: - arXiv: 2205.02597 - submitted to JHEP

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - pp -> Z + jets at 13 TeV with pT(jet) > 100 GeV

Cross-section measurements for a $Z$ boson produced in association with high-transverse-momentum jets ($p_\text{T}\geq 100$ GeV) and decaying into a charged-lepton pair ($e^+e^-$, $\mu^+\mu^-$) are presented. The measurements are performed using proton-proton collisions at $\sqrt{s} = 13$ TeV corresponding to an integrated luminosity of 139 fb${}^{-1}$ collected by the ATLAS experiment at the LHC. Measurements of angular correlations between the $Z$ boson and the closest jet are performed in events with at least one jet with $p_\text{T}\geq 500$ GeV. Event topologies of particular interest are the collinear emission of a $Z$ boson in dijet events and a boosted $Z$ boson recoiling against a jet. Fiducial cross sections are compared with state-of-the-art theoretical predictions. The data are found to agree with next-to-next-to-leading-order predictions by NNLOjet and with the next-to-leading-order multi-leg generators MadGraph5_aMC@NLO and Sherpa.

Source code:ATLAS_2022_I2077570.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// Collinear Z + Jets in pp at 13 TeV class ATLAS_2022_I2077570 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2022_I2077570);

/// Book histograms and initialise projections before the run
void init() {

  // Get options
  _mode = 0;
  if (getOption("LMODE") == "ELEL") _mode = 1;
  if (getOption("LMODE") == "MUMU") _mode = 2;

  // AntiKt4TruthWZJets prescription
  // Photons
  FinalState all_photons(Cuts::abspid == PID::PHOTON);

  // Muons
  PromptFinalState bare_mu(Cuts::abspid == PID::MUON, TauDecaysAs::PROMPT);
  LeptonFinder all_dressed_mu(bare_mu, all_photons, 0.1, Cuts::abseta < 2.5);

  // Electrons
  PromptFinalState bare_el(Cuts::abspid == PID::ELECTRON, TauDecaysAs::PROMPT);
  LeptonFinder all_dressed_el(bare_el, all_photons, 0.1, Cuts::abseta < 2.5);

  //Jet forming
  VetoedFinalState vfs(FinalState(Cuts::abseta < 4.5));
  vfs.addVetoOnThisFinalState(all_dressed_el);
  vfs.addVetoOnThisFinalState(all_dressed_mu);

  FastJets jet(vfs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::NONE);
  declare(jet, "Jets");


  // Current definition of leptons + jets
  PromptFinalState photons(Cuts::abspid == PID::PHOTON);
  PromptFinalState electrons(Cuts::abspid == PID::ELECTRON);
  PromptFinalState muons(Cuts::abspid == PID::MUON);

  // Kinematic cuts for leptons
  const Cut cuts_lep = Cuts::pT > 25 * GeV && Cuts::abseta < 2.5;

  LeptonFinder dressed_electrons(electrons, photons, 0.1, cuts_lep);
  declare(dressed_electrons, "DressedElectrons");

  LeptonFinder dressed_muons(muons, photons, 0.1, cuts_lep);
  declare(dressed_muons, "DressedMuons");


  book(_h["ZpT"], 1, 1, 1);
  book(_h["jetpT"], 2, 1, 1);
  book(_d["NJets"], 3, 1, 1);
  book(_d["NJets500"], 4, 1, 1);
  book(_h["minDR"], 5, 1, 1);
  book(_h["rZJ"], 6, 1, 1);
  book(_h["rZJ_coll"], 7, 1, 1);
  book(_h["rZJ_b2b"], 8, 1, 1);
  book(_d["NJets_coll"], 9, 1, 1);
  book(_d["NJets_b2b"], 10, 1, 1);
  book(_h["HT"], 11, 1, 1);
  book(_h["minDR600"], 12, 1, 1);
  book(_d["NJets600"], 13, 1, 1);
}

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


  // access fiducial electrons and muons
  const Particle *l1 = nullptr, *l2 = nullptr;
  auto muons = apply<LeptonFinder>(event, "DressedMuons").dressedLeptons();
  auto elecs = apply<LeptonFinder>(event, "DressedElectrons").dressedLeptons();

  // lepton-jet overlap removal (note: muons are not included in jet finding)
  // Jets eta < 2.5, pT > 30GeV for overlap removal
  Jets jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 30 * GeV && Cuts::absrap < 2.5);
  // Remove all jets within dR < 0.2 of a dressed lepton
  idiscardIfAnyDeltaRLess(jets, muons, 0.2);
  idiscardIfAnyDeltaRLess(jets, elecs, 0.2);

  // Remove leptons within dR < 0.4 of a jet
  idiscardIfAnyDeltaRLess(muons, jets, 0.4);
  idiscardIfAnyDeltaRLess(elecs, jets, 0.4);

  int nElecs = elecs.size();
  int nMuons = muons.size();

  if (nElecs + nMuons != 2) vetoEvent; // dilepton cut
  if (_mode == 2 && nMuons != 2) vetoEvent;
  if (_mode == 1 && nElecs != 2) vetoEvent;

  if (elecs.size() == 2) {
    l1 = &elecs[0];
    l2 = &elecs[1];
  }
  else if (muons.size() == 2) {
    l1 = &muons[0];
    l2 = &muons[1];
  }
  else
    vetoEvent;

  // if not e+e- or mu+mu- pair, veto
  if (l1->pid() + l2->pid() != 0) vetoEvent;

  // Dilepton selection :: Z mass peak.
  FourMomentum ll = (l1->mom() + l2->mom());
  double Zm = ll.mass();
  if (!inRange(Zm / GeV, 71.0, 111.0)) vetoEvent;
  double ZpT = ll.pT();

  // Calculate the observables
  double jet0pT = 0.;
  double cljetpT = 0.;
  double minDR = 99.;

  // Require jets to be above 100GeV
  iselect(jets, Cuts::pT > 100 * GeV);
  double HTjet = sum(jets, Kin::pT, 0.);
  for (const Jet& j : jets) {
    // find minDR and closest jet to Z boson, only with 100GeV+ jets
    double dr = deltaR(j, ll, RAPIDITY);
    if (dr < minDR) {
      minDR = dr;
      cljetpT = j.pT();
    }
  }
  const size_t Njets = jets.size();

  // NJets >= 1
  if (Njets < 1) vetoEvent;
  // Exclusive NJets, jet pT > 100 GeV

  _d["NJets"]->fill(Njets);

  // Z pT
  _h["ZpT"]->fill(ZpT / GeV);

  //Leading jet pT
  jet0pT = jets[0].pT();
  _h["jetpT"]->fill(jet0pT / GeV);

  // HT
  double HT = HTjet + l1->pT() + l2->pT();
  _h["HT"]->fill(HT / GeV);

  // HTJet > 600 GeV selection
  if (HTjet >= 600.) {
    double minDR_HTjet = 99.;
    // closest jet to Z
    for (const Jet& j : jets) {
      const double dr = deltaR(j, ll, RAPIDITY);
      if (dr < minDR_HTjet) minDR_HTjet = dr;
    }
    // Fill histograms of HTjet > 600 GeV
    _d["NJets600"]->fill(Njets);
    _h["minDR600"]->fill(minDR_HTjet);
  } // end of HTjet > 600 GeV

  // Our high pT phase-space
  if (jet0pT / GeV < 500.0) vetoEvent;

  // Exclusive NJets, jet pT > 500 GeV
  _d["NJets500"]->fill(Njets);

  // Z/J pT ratio
  _h["rZJ"]->fill(ZpT / cljetpT);
  _h["minDR"]->fill(minDR);

  // Phase space with DR<1.4
  if (minDR < 1.4) {
    _d["NJets_coll"]->fill(Njets);
    _h["rZJ_coll"]->fill(ZpT / cljetpT);
    // Phase space with DR>2.0
  }
  else if (minDR > 2.0) {
    _d["NJets_b2b"]->fill(Njets);
    _h["rZJ_b2b"]->fill(ZpT / cljetpT);
  }
}

void finalize() {
  double xsec = crossSectionPerEvent() / picobarn;
  // Analysis measures Z->ll(ee or mumu)
  // If file contains both Z->ee and Z->mumu, divide xs by 2
  if (_mode == 0) xsec *= 0.5;
  // Normalize to cross section.
  scale(_h, xsec);
  scale(_d, xsec);
} // end of finalize


// Define histograms
size_t _mode;
map<string, Histo1DPtr> _h;
map<string, BinnedHistoPtr<int>> _d;

};

RIVET_DECLARE_PLUGIN(ATLAS_2022_I2077570);

} ```