Rivet analyses
WW production at 13 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1734263
Status: VALIDATED
Authors: - Kristin Lohwasser - Christian Gutschow - Hannes Mildner
References: - Expt page: ATLAS-STDM-2017-24 - arXiv: 1905.04242
Beams: p+ p+
Beam energies: (6500.0, 6500.0)GeV
Run details: - pp -> WW production at 13 TeV
A measurement of fiducial and differential cross-sections for W+W− production in proton–proton collisions at $=$13~TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 36.1~fb−1 is presented. Events with one electron and one muon are selected, corresponding to the decay of the diboson system as WW → e±νμ∓ν. To suppress top-quark background, events containing jets with a transverse momentum exceeding 35~GeV are not included in the measurement phase space. The fiducial cross-section, six differential distributions and the cross-section as a function of the jet-veto transverse momentum threshold are measured and compared with several theoretical predictions. Constraints on anomalous electroweak gauge boson self-interactions are also presented in the framework of a dimension-six effective field theory.
Source
code:ATLAS_2019_I1734263.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/MissingMomentum.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/LeptonFinder.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
namespace Rivet {
/// @brief WW production at 13 TeV
class ATLAS_2019_I1734263 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2019_I1734263);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
const FinalState fs(Cuts::abseta < 5.);
// Project photons for dressing
FinalState photon_id(Cuts::abspid == PID::PHOTON);
// Cuts for leptons
Cut lepton_cuts = (Cuts::abseta < 2.5) && (Cuts::pT > 27*GeV);
// Lepton for simplified phase space (e.g. for comparison with CMS)
Cut lepton_cuts_simpl = (Cuts::abseta < 2.5) && (Cuts::pT > 25*GeV);
// Project dressed leptons (e/mu not from tau) with pT > 27 GeV and |eta| < 2.5
// Both for normal and simplified phase space
PromptFinalState lep_bare(Cuts::abspid == PID::MUON || Cuts::abspid == PID::ELECTRON);
LeptonFinder lep_dressed(lep_bare, photon_id, 0.1, lepton_cuts);
declare(lep_dressed,"lep_dressed");
LeptonFinder lep_dressed_simpl(lep_bare, photon_id, 0.1, lepton_cuts_simpl);
declare(lep_dressed_simpl,"lep_dressed_simpl");
// Get MET
MissingMomentum mm(fs);
declare(mm, "met");
// Define hadrons as everything but dressed leptons (for jet clustering)
VetoedFinalState hadrons(fs);
hadrons.addVetoOnThisFinalState(lep_dressed);
declare(hadrons, "hadrons");
VetoedFinalState hadrons_simpl(fs);
hadrons_simpl.addVetoOnThisFinalState(lep_dressed_simpl);
declare(hadrons_simpl, "hadrons_simpl");
// Project jets
FastJets jets(hadrons, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::NONE);
declare(jets, "jets");
FastJets jets_simpl(hadrons_simpl, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::NONE);
declare(jets_simpl, "jets_simpl");
// Book histograms
// fiducial differential cross section as a function of the jet-veto pt cut
book(_d, 1, 1, 1);
// fiducial differential cross section (leading lepton pt)
book(_h["ptlead"], 4, 1, 1);
book(_h["ptlead_norm"], 22, 1, 1);
book(_h["ptlead_simpl"], 41, 1, 1);
// fiducial differential cross section (dilepton-system mll)
book(_h["mll"], 7, 1, 1);
book(_h["mll_norm"], 25, 1, 1);
book(_h["mll_simpl"], 42, 1, 1);
// fiducial differential cross section (dilepton-system ptll)
book(_h["ptll"], 10, 1, 1);
book(_h["ptll_norm"], 28, 1, 1);
book(_h["ptll_simpl"], 43, 1, 1);
// fiducial differential cross section (absolute rapidity of dilepton-system y_ll)
book(_h["yll"], 13, 1, 1);
book(_h["yll_norm"], 31, 1, 1);
// fiducial differential cross section (dilepton-system delta_phi_ll)
book(_h["dphill"], 16, 1, 1);
book(_h["dphill_norm"], 34, 1, 1);
// fiducial differential cross section (absolute costheta* of dilepton-system costhetastar_ll)
book(_h["costhetastarll"], 19, 1, 1);
book(_h["costhetastarll_norm"], 37, 1, 1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Get met and find leptons
const MissingMomentum& met = apply<MissingMomentum>(event, "met");
const DressedLeptons &leptons = apply<LeptonFinder>(event, "lep_dressed").dressedLeptons();
const DressedLeptons &leptons_simpl = apply<LeptonFinder>(event, "lep_dressed_simpl").dressedLeptons();
// Find jets and jets for simplified phase space (for the latter slightly different leptons are excluded from clustering)
const Jets& jets30 = apply<FastJets>(event, "jets").jetsByPt(Cuts::abseta < 4.5 && Cuts::pT > 30*GeV);
const Jets& jets_simpl = apply<FastJets>(event, "jets_simpl").jetsByPt(Cuts::abseta < 4.5 && Cuts::pT > 30*GeV);
// 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;
// Define observables for simplified PS
const FourMomentum dilep_simpl = leptons_simpl.size()>1 ? leptons_simpl[0].momentum() + leptons_simpl[1].momentum() : FourMomentum(0,0,0,0);
const double ptll_simpl = leptons_simpl.size()>1 ? dilep_simpl.pT()/GeV : -1;
const double Mll_simpl = leptons_simpl.size()>1 ? dilep_simpl.mass()/GeV : -1;
// Cuts for simplified PS
bool veto_simpl = false;
// Remove events that do not contain 2 good leptons (either muons or electrons)
if ( leptons_simpl.size() != 2 ) veto_simpl = true;
// Veto same-flavour events
else if ( leptons_simpl[0].abspid() == leptons_simpl[1].abspid()) veto_simpl = true;
// Veto same-charge events
else if ( leptons_simpl[0].pid()*leptons_simpl[1].pid()>0) veto_simpl = true;
// MET (pt-MET) cut
else if (met.missingPt() <= 20*GeV) veto_simpl = true;
// jetveto
else if ( !jets_simpl.empty() ) veto_simpl = true;
// Fill histos for simplified phase space
if ( !veto_simpl ){
_h["ptlead_simpl"]->fill(leptons_simpl[0].pT()/GeV);
_h["ptll_simpl"]->fill(ptll_simpl);
_h["mll_simpl"]->fill(Mll_simpl);
}
// Event selection for proper fiducial phase space
// Remove events that do not contain 2 good leptons (either muons or electrons)
if ( leptons.size() != 2) 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;
// MET (pt-MET) cut
if (met.missingPt() <= 20*GeV) vetoEvent;
// m_ll cut
if (dilep.mass() <= 55*GeV) vetoEvent;
// pt_ll cut
if (dilep.pT() <= 30*GeV) vetoEvent;
// Fill cross section as function of veto-jet pt before applying jet veto
if (jets30.empty() || jets30[0].pT()/GeV < 30.) _d->fill(30);
if (jets30.empty() || jets30[0].pT()/GeV < 35.) _d->fill(35);
if (jets30.empty() || jets30[0].pT()/GeV < 40.) _d->fill(40);
if (jets30.empty() || jets30[0].pT()/GeV < 45.) _d->fill(45);
if (jets30.empty() || jets30[0].pT()/GeV < 50.) _d->fill(50);
if (jets30.empty() || jets30[0].pT()/GeV < 55.) _d->fill(55);
if (jets30.empty() || jets30[0].pT()/GeV < 60.) _d->fill(60);
// Jet veto at 35 GeV is the default
if (!jets30.empty() && jets30[0].pT()/GeV > 35.) vetoEvent;
// fill histograms
_h["ptlead"]->fill(leptons[0].pT()/GeV);
_h["ptlead_norm"]->fill(leptons[0].pT()/GeV);
_h["ptll"]->fill(ptll);
_h["ptll_norm"]->fill(ptll);
_h["mll"]->fill(Mll);
_h["mll_norm"]->fill(Mll);
_h["yll"]->fill(Yll);
_h["yll_norm"]->fill(Yll);
_h["dphill"]->fill(DPhill);
_h["dphill_norm"]->fill(DPhill);
_h["costhetastarll"]->fill(costhetastar);
_h["costhetastarll_norm"]->fill(costhetastar);
}
/// Normalise histograms etc., after the run
void finalize() {
const double sf(crossSection()/femtobarn/sumOfWeights());
// scale histogram by binwidth, as bin content is actually a integrated fiducial cross section
// scale to cross section
scale(_d, sf);
for (auto& hist : _h) {
scale(hist.second, sf);
if (hist.first.find("norm") != string::npos) normalize(hist.second);
}
}
/// @}
private:
/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
BinnedHistoPtr<int> _d;
/// @}
};
RIVET_DECLARE_PLUGIN(ATLAS_2019_I1734263);
}