Rivet analyses

title: ATLAS_2022_I2103950

WW production in pp at 13 TeV in electroweak SUSY inspired phase space

Experiment: ATLAS (LHC)

Inspire ID: 2103950

Status: VALIDATED

Authors: - Sarah Louise Williams

References: - arXiv: 2206.15231 - Eur.Phys.J.C 83 (2023) 718, 2023 - Expt page: ATLAS-SUSY-2021-06

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - WW + 0-jet production

This paper presents a measurement of fiducial and differential cross-sections for $W^+W^-$ production in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS experiment at the Large Hadron Collider using a dataset corresponding to an integrated luminosity of 139 fb${}^{-1}$. Events with exactly one electron, one muon and no hadronic jets are studied. The fiducial region in which the measurements are performed is inspired by searches for the electroweak production of supersymmetric charginos decaying to two-lepton final states. The selected events have moderate values of missing transverse momentum and the 'stransverse mass' variable $m_\mathrm{T2}$, which is widely used in searches for supersymmetry at the LHC. The ranges of these variables are chosen so that the acceptance is enhanced for direct $W^+W^-$ production and suppressed for production via top quarks, which is treated as a background. The fiducial cross-section and particle-level differential cross-sections for six variables are measured and compared with two theoretical SM predictions from perturbative QCD calculations.

Source code:ATLAS_2022_I2103950.cc

```c++ // -- 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/MissingMomentum.hh"

include "Rivet/Projections/PromptFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

include "Rivet/Tools/RivetMT2.hh"

namespace Rivet {

/// @brief WW production in pp at 13 TeV in electroweak SUSY-inspired phase space class ATLAS_2022_I2103950 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2022_I2103950);


/// @name Analysis methods
/// @{

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

  const FinalState fs(Cuts::abseta < 5);

  // Project photons for dressing
  FinalState photons(Cuts::abspid == PID::PHOTON);

  // Cuts for leptons
  Cut lepton_cuts = ((Cuts::abseta < 2.6 && Cuts::abspid == PID::MUON)
                     || (Cuts::abseta < 2.47 && Cuts::abspid == PID::ELECTRON));

  // Muons
  PromptFinalState bare_mu(Cuts::abspid == PID::MUON, TauDecaysAs::PROMPT);
  LeptonFinder all_dressed_mu(bare_mu, photons, 0.1);

  // Electrons
  PromptFinalState bare_el(Cuts::abspid == PID::ELECTRON, TauDecaysAs::PROMPT);
  LeptonFinder all_dressed_el(bare_el, photons, 0.1);

  //Jet forming
  VetoedFinalState vfs(FinalState(Cuts::abseta < 5));

  InvisibleFinalState prompt_invis(OnlyPrompt::YES, TauDecaysAs::PROMPT);
  vfs.addVetoOnThisFinalState(prompt_invis);
  vfs.addVetoOnThisFinalState(all_dressed_el);
  vfs.addVetoOnThisFinalState(all_dressed_mu);

  FastJets jets(vfs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::DECAY);
  declare(jets, "jets");


  // Project dressed leptons (e/mu not from tau) with pT > 25 GeV
  PromptFinalState lep_bare(Cuts::abspid == PID::MUON || Cuts::abspid == PID::ELECTRON,
                            TauDecaysAs::PROMPT);
  declare(lep_bare, "lep_bare");
  PromptFinalState prompt_mu(Cuts::abspid == PID::MUON, TauDecaysAs::PROMPT);
  PromptFinalState prompt_el(Cuts::abspid == PID::ELECTRON, TauDecaysAs::PROMPT);

  LeptonFinder lep_dressed(lep_bare, photons, 0.1, lepton_cuts);
  declare(lep_dressed, "lep_dressed");
  LeptonFinder elecs(prompt_el, photons, 0.1, lepton_cuts);
  declare(elecs, "elecs");
  LeptonFinder muons(prompt_mu, photons, 0.1, lepton_cuts);
  declare(muons, "muons");

  // Get MET from generic invisibles
  VetoedFinalState ivfs(fs);
  ivfs.addVetoOnThisFinalState(VisibleFinalState(fs));
  declare(ivfs, "InvisibleFS");

  // fiducial differential cross sections
  book(_h["ptlead"], 13, 1, 1);
  book(_h["mll"], 15, 1, 1);
  book(_h["ptll"], 17, 1, 1);
  book(_h["yll"], 7, 1, 1);
  book(_h["dphill"], 9, 1, 1);
  book(_h["costhetastarll"], 11, 1, 1);
}


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


  const FinalState& ifs = apply<VetoedFinalState>(event, "InvisibleFS");
  const FourMomentum metinvisible = sum(ifs.particles(), FourMomentum());

  // Get met and find leptons
  //const DressedLeptons &leptons = apply<LeptonFinder>(event, "lep_dressed").dressedLeptons();
  const DressedLeptons& all_elecs = apply<LeptonFinder>(event, "elecs").dressedLeptons();
  const DressedLeptons& all_muons = apply<LeptonFinder>(event, "muons").dressedLeptons();
  //Particles bare_leps  = apply<IdentifiedFinalState>(event, "bare_leptons").particles();

  // Find jets and jets for simplified phase space (for the latter slightly different leptons are excluded from clustering)
  Jets alljets = apply<FastJets>(event, "jets").jetsByPt(Cuts::abseta < 4.5 && Cuts::pT > 20 * GeV);

  DressedLeptons elecs_muonOR;
  for (const DressedLepton& el : all_elecs) {
    bool overlaps = false;
    for (const DressedLepton& mu : all_muons) {
      if (deltaR(el, mu) < 0.01) {
        overlaps = true;
        break;
      }
    }
    if (overlaps) continue;
    elecs_muonOR.push_back(el);
  }

  // jet electron overlap removal
  for (const DressedLepton& e : elecs_muonOR) {
    idiscard(alljets, deltaRLess(e, 0.2, RAPIDITY));
  }

  // muon jet overlap removal
  DressedLeptons muons;
  for (const DressedLepton& mu : all_muons) {
    float dRcut = 0.4;
    if ((0.04 + 10.0 / mu.pT()) < 0.4) {
      dRcut = 0.04 + 10.0 / mu.pT();
    }
    bool overlaps = false;
    for (const Jet& jet : alljets) {
      if (deltaR(mu, jet) < dRcut) {
        overlaps = true;
        break;
      }
    }
    if (overlaps) continue;
    muons.push_back(mu);
  }
  // electron jet overlap removal
  DressedLeptons elecs;
  for (const DressedLepton& el : elecs_muonOR) {
    float dRcut = 0.4;
    if ((0.04 + 10 / el.pT()) < 0.4) {
      dRcut = 0.04 + 10 / el.pT();
    }
    bool overlaps = false;
    for (const Jet& jet : alljets) {
      if (deltaR(el, jet) < dRcut) {
        overlaps = true;
        break;
      }
    }
    if (overlaps) continue;
    elecs.push_back(el);
  }
  Jets jets20;
  for (const Jet& jet : alljets) {
    if (jet.abseta() < 2.4) jets20 += jet;
  }
  // Remove events that do not contain 2 good leptons (either muons or electrons)
  if ((elecs.size() + muons.size()) != 2) vetoEvent;
  // only select electron-muon events
  if (elecs.size() != 1) vetoEvent;
  DressedLeptons leptons;
  if (elecs[0].pT() > muons[0].pT()) {
    leptons.push_back(elecs[0]);
    leptons.push_back(muons[0]);
  }
  else {
    leptons.push_back(muons[0]);
    leptons.push_back(elecs[0]);
  }


  // Define observables
  const FourMomentum dilep = leptons.size() > 1 ? leptons[0].momentum() + leptons[1].momentum()
                                                : FourMomentum(0, 0, 0, 0);
  const double ptll = leptons.size() > 1 ? dilep.pT() / GeV : -1;
  const double Mll = leptons.size() > 1 ? dilep.mass() / GeV : -1;
  const double Yll = leptons.size() > 1 ? dilep.absrap() : -5;
  const double DPhill = leptons.size() > 1 ? fabs(deltaPhi(leptons[0], leptons[1])) : -1.;
  const double costhetastar = leptons.size() > 1 ? fabs(tanh((leptons[0].eta() - leptons[1].eta()) / 2))
                                                 : -0.2;

  const double mt2 = leptons.size() > 1 ? mT2(leptons[0], leptons[1], metinvisible, 0) : 0;

  // Event selection for proper fiducial phase space
  if (leptons.size() != 2) vetoEvent;
  if (leptons[0].pT() < 25 * GeV || leptons[1].pT() < 25 * GeV) vetoEvent;

  // Veto same-flavour events
  if (leptons[0].abspid() == leptons[1].abspid()) vetoEvent;

  // Veto same-charge events
  if (leptons[0].pid() * leptons[1].pid() > 0) vetoEvent;

  // jet veto
  if (!(jets20.size() == 0)) vetoEvent;

  if (metinvisible.pT() <= 60 * GeV || metinvisible.pT() > 80 * GeV) vetoEvent;

  // m_ll cut
  if (dilep.mass() <= 100 * GeV) vetoEvent;

  //mt2 cut
  if ((mt2 <= 60 * GeV) || (mt2 > 80 * GeV)) vetoEvent;

  // Jet veto at 35 GeV is the default
  if (!jets20.empty()) vetoEvent;

  // fill histograms

  _h["ptlead"]->fill(leptons[0].pT() / GeV);
  _h["ptll"]->fill(ptll);
  _h["mll"]->fill(Mll);
  _h["yll"]->fill(Yll);
  _h["dphill"]->fill(DPhill);
  _h["costhetastarll"]->fill(costhetastar);
}


/// Normalise histograms etc., after the run
void finalize() {
  const double sf(crossSection() / femtobarn / sumOfWeights());
  // scale to cross section
  scale(_h, sf);
}

/// @}

private:

/// Histograms
map<string, Histo1DPtr> _h;

};

RIVET_DECLARE_PLUGIN(ATLAS_2022_I2103950);

} ```