Rivet analyses
WW production at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1426515
Status: VALIDATED
Authors: - Kristin Lohwasser - Christian Gutschow
References: - Expt page: ATLAS-STDM-2013-07 - JHEP 1609 (2016) 029 - DOI: 10.1007/JHEP09(2016)029 - arXiv: 1603.01702
Beams: p+ p+
Beam energies: (4000.0, 4000.0)GeV
Run details: - pp -> WW production at 8 TeV
The production of W boson pairs in proton–proton collisions at $\sqrt{s} = 8$ TeV is studied using data corresponding to 20.3 fb−1 of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The W bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 WW candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the W branching fractions to leptons in order to obtain the total WW production cross section, which is found to be 71.1 ± 1.1 (stat) −5.0+5.7 (syst) ±1.4 (lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2−1.4+1.6 (scale) ±1.2 (PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.
Source
code:ATLAS_2016_I1426515.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/LeptonFinder.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"
namespace Rivet {
/// WW production at 8 TeV
class ATLAS_2016_I1426515 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2016_I1426515);
/// Book histograms and initialise projections before the run
void init() {
const FinalState fs(Cuts::abseta < 4.5);
// Project photons for dressing
IdentifiedFinalState photon_id(fs);
photon_id.acceptIdPair(PID::PHOTON);
// Project dressed electrons with pT > 15 GeV and |eta| < 2.47
PromptFinalState el_bare(FinalState(Cuts::abspid == PID::ELECTRON));
Cut cuts = (Cuts::abseta < 2.47) && ( (Cuts::abseta <= 1.37) || (Cuts::abseta >= 1.52) ) && (Cuts::pT > 10*GeV);
LeptonFinder el_dressed_FS(el_bare, photon_id, 0.1, cuts);
declare(el_dressed_FS, "EL_DRESSED_FS");
// Project dressed muons with pT > 15 GeV and |eta| < 2.5
PromptFinalState mu_bare(FinalState(Cuts::abspid == PID::MUON));
LeptonFinder mu_dressed_FS(mu_bare, photon_id, 0.1, Cuts::abseta < 2.4 && Cuts::pT > 15*GeV);
declare(mu_dressed_FS, "MU_DRESSED_FS");
Cut cuts_WW = (Cuts::abseta < 2.5) && (Cuts::pT > 20*GeV);
IdentifiedFinalState lep_id(fs);
lep_id.acceptIdPair(PID::MUON);
lep_id.acceptIdPair(PID::ELECTRON);
PromptFinalState lep_bare(lep_id);
LeptonFinder leptons(lep_bare, photon_id, 0.1, cuts_WW);
declare(leptons,"leptons");
declare(FinalState(Cuts::abspid == PID::TAU || Cuts::abspid == PID::NU_TAU), "tau_id");
// Get MET from generic invisibles
VetoedFinalState ivfs(fs);
ivfs.addVetoOnThisFinalState(VisibleFinalState(fs));
declare(ivfs, "InvisibleFS");
// Project jets
FastJets jets(fs, JetAlg::ANTIKT, 0.4, JetMuons::NONE, JetInvisibles::NONE);
declare(jets, "jets");
// Integrated cross sections
// d01 ee/mm fiducial integrated cross sections
book(_hist_mm_fid_intxsec, 1, 1, 1);
book(_hist_ee_fid_intxsec, 1, 1, 2);
// d02 emme fiducial integrated cross sections
book(_hist_emme_fid_intxsec, 2, 1, 1);
// d10 emme fiducial differential cross section (leading lepton ptlead + ptlead normalized)
book(_hist_emme_fid_ptlead, 10, 1, 1);
book(_hist_emme_fid_ptleadnorm, 10, 1, 2);
// d11 emme fiducial differential cross section (dilepton-system ptll + ptll normalized)
book(_hist_emme_fid_ptll, 11, 1, 1);
book(_hist_emme_fid_ptllnorm, 11, 1, 2);
// d12 emme fiducial differential cross section (dilepton-system mll + mll normalized)
book(_hist_emme_fid_mll, 12, 1, 1);
book(_hist_emme_fid_mllnorm, 12, 1, 2);
// d13 emme fiducial differential cross section (dilepton-system delta_phi_ll + dphill normalized)
book(_hist_emme_fid_dphill, 13, 1, 1);
book(_hist_emme_fid_dphillnorm, 13, 1, 2);
// d14 emme fiducial differential cross section (absolute rapidity of dilepton-system y_ll + y_ll normalized)
book(_hist_emme_fid_yll, 14, 1, 1);
book(_hist_emme_fid_yllnorm, 14, 1, 2);
// d15 emme fiducial differential cross section (absolute costheta* of dilepton-system costhetastar_ll + costhetastar_ll normalized)
book(_hist_emme_fid_costhetastarll, 15, 1, 1);
book(_hist_emme_fid_costhetastarllnorm, 15, 1, 2);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Find leptons
const FinalState& ifs = apply<VetoedFinalState>(event, "InvisibleFS");
const DressedLeptons& leptons = apply<LeptonFinder>(event, "leptons").dressedLeptons();
const DressedLeptons& good_mu = apply<LeptonFinder>(event, "MU_DRESSED_FS").dressedLeptons();
const DressedLeptons& good_el = apply<LeptonFinder>(event, "EL_DRESSED_FS").dressedLeptons();
const Jets& jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 4.5);
// Taus are excluded from the fiducial cross section
const Particles taus = apply<FinalState>(event, "tau_id").particlesByPt(Cuts::pT>12.*GeV && Cuts::abseta < 3.0);
if (!taus.empty()) vetoEvent;
// Remove events that do not contain 2 good leptons (either muons or electrons)
if (leptons.size() != 2 && (good_el.size() != 1 || good_mu.size() != 1)) vetoEvent;
// Split into channels
int channel = -1; // 1=mm, 2=ee; 3=emu; 4=mue
if (good_mu.size() == 2) channel = 1; //mm
else if (good_el.size() == 2) channel = 2; //ee
else if (good_mu.size() == 1 && good_el.size() == 1 && good_el[0].pT() > good_mu[0].pT()) channel = 3; //emu
else if (good_mu.size() == 1 && good_el.size() == 1 && good_el[0].pT() < good_mu[0].pT()) channel = 4; //mue
if (channel == -1) vetoEvent;
// Assign leptons
const DressedLepton *lep1, *lep2;
if (channel == 1) { //mm
if (good_mu[0].pT() > good_mu[1].pT()) {
lep1 = &good_mu[0];
lep2 = &good_mu[1];
} else {
lep1 = &good_mu[1];
lep2 = &good_mu[0];
}
}
else if (channel == 2) { //ee
if (good_el[0].pT() > good_el[1].pT()) {
lep1 = &good_el[0];
lep2 = &good_el[1];
} else {
lep1 = &good_el[1];
lep2 = &good_el[0];
}
}
else if (channel == 3) { //emu
lep1 = &good_el[0];
lep2 = &good_mu[0];
}
else { // if (channel == 4) { //mue
lep1 = &good_mu[0];
lep2 = &good_el[0];
}
// Cut on leptons
if (lep1->pT() < 25*GeV || lep2->pT() < 20*GeV) vetoEvent;
// Select jets isolated from electrons
const Jets jets_selected = select(jets, [&](const Jet& j){ return all(good_el, deltaRGtr(j, 0.3)); });
// Define variables
const FourMomentum met = sum(ifs.particles(), FourMomentum());
const FourMomentum dilep = lep1->momentum() + lep2->momentum();
const double ptll = dilep.pT()/GeV;
const double Mll = dilep.mass()/GeV;
const double Yll = dilep.absrap();
const double DPhill = fabs(deltaPhi(*lep1, *lep2));
const double costhetastar = fabs(tanh((lep1->eta() - lep2->eta()) / 2));
// Calculate dphi to MET
double DPhi_met = fabs(deltaPhi((*lep1), met));
if (fabs(deltaPhi( (*lep2), met)) < DPhi_met) DPhi_met = fabs(deltaPhi((*lep2), met));
if (DPhi_met > M_PI/2) DPhi_met = 1.; else DPhi_met = fabs(sin(DPhi_met));
// Apply selections
// mll lower cut (reject quarkonia)
if ((channel == 1 || channel == 2) && Mll < 15.) vetoEvent;
else if (Mll < 10.) vetoEvent;
// Z veto (reject Z -- only dilepton channels)
if ((channel == 1 || channel == 2) && abs(Mll - 91.1876) < 15.) vetoEvent;
// Met rel cut
if ((channel == 1 || channel == 2) && met.pT()*DPhi_met < 45*GeV) vetoEvent;
else if (met.pT()*DPhi_met < 15*GeV) vetoEvent;
// MET (pt-MET) cut
if ((channel == 1 || channel == 2) && met.pT() <= 45*GeV) vetoEvent; // begin MET cut
else if (met.pT() <= 20*GeV) vetoEvent;
// Require 0 jets
if (!jets_selected.empty()) vetoEvent;
// Fill histograms
if (channel == 1) {
_hist_mm_fid_intxsec->fill(1.0);
} else if (channel == 2) {
_hist_ee_fid_intxsec->fill(1.0);
} else if (channel == 3 || channel == 4) {
_hist_emme_fid_intxsec->fill(1.0);
_hist_emme_fid_ptlead->fill(lep1->pT()/GeV);
_hist_emme_fid_ptleadnorm->fill(lep1->pT()/GeV);
_hist_emme_fid_ptll->fill(ptll);
_hist_emme_fid_ptllnorm->fill(ptll);
_hist_emme_fid_mll->fill(Mll);
_hist_emme_fid_mllnorm->fill(Mll);
_hist_emme_fid_dphill->fill(DPhill);
_hist_emme_fid_dphillnorm->fill(DPhill);
_hist_emme_fid_yll->fill(Yll);
_hist_emme_fid_yllnorm->fill(Yll);
_hist_emme_fid_costhetastarll->fill(costhetastar);
_hist_emme_fid_costhetastarllnorm->fill(costhetastar);
}
}
/// Normalise histograms etc., after the run
void finalize() {
const double sf(crossSection()/femtobarn/sumOfWeights());
scale(_hist_mm_fid_intxsec, sf); scale(_hist_ee_fid_intxsec, sf);
scale(_hist_emme_fid_intxsec, sf); scale(_hist_emme_fid_ptlead, sf);
scale(_hist_emme_fid_ptll, sf); scale(_hist_emme_fid_mll, sf);
scale(_hist_emme_fid_dphill, sf); scale(_hist_emme_fid_yll, sf);
scale(_hist_emme_fid_costhetastarll, sf);
normalize(_hist_emme_fid_ptleadnorm); normalize(_hist_emme_fid_ptllnorm);
normalize(_hist_emme_fid_mllnorm); normalize(_hist_emme_fid_dphillnorm);
normalize(_hist_emme_fid_yllnorm); normalize(_hist_emme_fid_costhetastarllnorm);
}
private:
/// @name Histograms
/// @{
// d01 ee/mm fiducial integrated cross sections
Histo1DPtr _hist_mm_fid_intxsec, _hist_ee_fid_intxsec;
// d02 emme fiducial integrated cross sections
Histo1DPtr _hist_emme_fid_intxsec;
// d10 emme fiducial differential cross section (leading lepton ptlead + ptlead normalized)
Histo1DPtr _hist_emme_fid_ptlead, _hist_emme_fid_ptleadnorm;
// d11 emme fiducial differential cross section (dilepton-system ptll + ptll normalized)
Histo1DPtr _hist_emme_fid_ptll, _hist_emme_fid_ptllnorm;
// d12 emme fiducial differential cross section (dilepton-system mll + mll normalized)
Histo1DPtr _hist_emme_fid_mll, _hist_emme_fid_mllnorm;
// d13 emme fiducial differential cross section (dilepton-system delta_phi_ll + dphill normalized)
Histo1DPtr _hist_emme_fid_dphill, _hist_emme_fid_dphillnorm;
// d14 emme fiducial differential cross section (absolute rapidity of dilepton-system y_ll + y_ll normalized)
Histo1DPtr _hist_emme_fid_yll, _hist_emme_fid_yllnorm;
// d15 emme fiducial differential cross section (absolute costheta* of dilepton-system costhetastar_ll + costhetastar_ll normalized)
Histo1DPtr _hist_emme_fid_costhetastarll, _hist_emme_fid_costhetastarllnorm;
/// @}
};
RIVET_DECLARE_PLUGIN(ATLAS_2016_I1426515);
}