Rivet analyses

title: CMS_2024_I2796231

$\mathrm{W}^{+}\mathrm{W^{-}}$ boson pair production in proton-proton collisions at 13.6 TeV

Experiment: CMS (LHC)

Inspire ID: 2796231

Status: VALIDATED

Authors: - cms-pag-conveners-smp@cern.ch - Guillelmo Gomez-Ceballos

References: - arXiv: 2406.05101 - Expt page: CMS-SMP-24-001 - Phys. Lett. B 861 (2025) 139231

Beams: p+ p+

Beam energies: (6800.0, 6800.0)GeV

Run details: - pp to $\mathrm{W}^{+}\mathrm{W^{-}}$ interactions at $\sqrt{s}=13.6~\mathrm{TeV}$. Data collected by CMS during the year 2022.

First measurements of the opposite-sign $\mathrm{W}$ boson pair production cross section in proton-proton collisions at $\sqrt{s}=13.6~\mathrm{TeV}$ are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of $34.8~\mathrm{fb}^{-1}$. Events are selected by requiring one electron and one muon of opposite charges. A maximum likelihood fit is performed in event signal- and background-enriched categories defined by the flavour and charge of the leptons, the number of jets, and number of jets identified as originating from b quarks. An inclusive $\mathrm{W}^{+}\mathrm{W^{-}}$ production cross section of $125.7 \pm 5.6$ pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event.

Source code:CMS_2024_I2796231.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/LeptonFinder.hh"

include "Rivet/Projections/MissingMomentum.hh"

include "Rivet/Projections/PromptFinalState.hh"

namespace Rivet {

/// @brief W+W- boson pair production in pp collisions at 13.6 TeV class CMS_2024_I2796231 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2024_I2796231);

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

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

  // Initialise and register projections

  // The basic final-state projection:
  // all final-state particles within
  // the given eta acceptance
  const FinalState fs(Cuts::abseta < 5.0);
  const FinalState fsjet2p5(Cuts::abseta < 2.5);

  // The final-state particles declared above are clustered using FastJet with
  // the anti-kT algorithm and a jet-radius parameter 0.4
  // muons and neutrinos are excluded from the clustering
  FastJets jet2p5fs(fsjet2p5, JetAlg::ANTIKT, 0.4);
  declare(jet2p5fs, "jets2p5");

  // FinalState of prompt photons and bare muons and electrons in the event
  PromptFinalState photons(Cuts::abspid == PID::PHOTON);
  PromptFinalState bare_leps(Cuts::abspid == PID::MUON || Cuts::abspid == PID::ELECTRON);
  bare_leps.acceptTauDecays(false);

  // Dress the prompt bare leptons with prompt photons within dR < 0.1,
  // and apply some fiducial cuts on the dressed leptons
  Cut lepton_cuts = Cuts::abseta < 2.5 && Cuts::pT > 10 * GeV;
  LeptonFinder dressed_leps(bare_leps, photons, 0.1, lepton_cuts);
  declare(dressed_leps, "leptons");

  // Book histograms
  book(_h_WW_njets_norm, 3, 1, 1);
  book(_h_WW_njets, 5, 1, 1);
}

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

  if (_edges.empty()) {
    _edges = _h_WW_njets_norm->xEdges();
  }

  // Retrieve dressed leptons, sorted by pT
  Particles leptons = apply<LeptonFinder>(event, "leptons").particlesByPt();

  // Apply a lepton size requirement
  if (leptons.size() != 2) return;

  // Retrieve clustered jets, sorted by pT, with a minimum pT cut
  Jets jetsNj = apply<FastJets>(event, "jets2p5").jetsByPt(Cuts::pT > 30 * GeV);

  // Remove all jets within dR < 0.4 of a dressed lepton
  idiscardIfAnyDeltaRLess(jetsNj, leptons, 0.4);

  if (leptons.size() == 2 && leptons[0].pid() * leptons[1].pid() < 0
      && abs(leptons[0].pid()) != abs(leptons[1].pid())) {
    FourMomentum dilCand = leptons[0].momentum() + leptons[1].momentum();
    if (dilCand.mass() > 85 * GeV) {
      double ptlmax = leptons[0].pT();
      double ptlmin = leptons[1].pT();
      if (ptlmax < ptlmin) {
        ptlmax = leptons[1].pT();
        ptlmin = leptons[0].pT();
      }
      if (ptlmax > 25 * GeV && ptlmin > 20 * GeV) {
        _h_WW_njets->fill(_edges[min((int)jetsNj.size(), 2)]);
        _h_WW_njets_norm->fill(_edges[min((int)jetsNj.size(), 2)]);
      } // ptlmax > 25 && ptmin > 20
    } // mll > 85
  } // different-flavor leptons
}

/// Normalise histograms etc., after the run
void finalize() {

  double norm = (sumOfWeights() != 0) ? crossSection() / picobarn / sumOfWeights() : 1.0;
  normalize(_h_WW_njets_norm);
  scale(_h_WW_njets, norm);
}

/// @}

/// @name Histograms
/// @{
BinnedHistoPtr<string> _h_WW_njets_norm;
BinnedHistoPtr<string> _h_WW_njets;
vector<string> _edges;
/// @}

};

RIVET_DECLARE_PLUGIN(CMS_2024_I2796231);

} ```