Rivet analyses
title: CMS_2016_I1487288
$WZ$ production cross-section in $pp$ collisions at 8~TeV
Experiment: CMS (LHC)
Inspire ID: 1487288
Status: VALIDATED
Authors: - Shehu AbdusSalam - Andy Buckley
References: - Eur.Phys.J. C77 (2017) no.4, 236 - DOI:10.1140/epjc/s10052-017-4730-z - Expt page: CMS-SMP-14-014 - CERN-EP-2016-205 - arXiv: 1609.05721
Beams: p+ p+
Beam energies: (4000.0, 4000.0)GeV
Run details: - WZ events at 8 TeV
Fully leptonic $WZ$ diboson production at the CMS experiment, measured inclusively at 7 and 8~TeV, and differentially at 8 TeV only (this analysis). The differential cross-sections are measured with respect to $Z$ $p_T$, leading jet $p_T$, and the jet multiplicity. This data is useful for constraining MC models of QCD and EW activity in diboson events, and for constraining anomalous couplings. NOTE: total cross-section is fixed to the measured value in this analysis, since the correction factors from fiducial to inclusive $WZ$ production were not published.
Source code:CMS_2016_I1487288.cc
```c++
include "Rivet/Analysis.hh"
include "Rivet/Projections/DileptonFinder.hh"
include "Rivet/Projections/FastJets.hh"
include "Rivet/Projections/FinalState.hh"
include "Rivet/Projections/LeptonFinder.hh"
include "Rivet/Projections/MissingMomentum.hh"
namespace Rivet {
/// WZ production cross section in pp collisions at 7 and 8 TeV class CMS_2016_I1487288 : public Analysis { public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2016_I1487288);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
FinalState fs(Cuts::abseta < 4.9);
FastJets fj(fs, JetAlg::ANTIKT, 0.5, JetMuons::ALL, JetInvisibles::DECAY);
declare(fj, "Jets");
DileptonFinder zeeFinder(91.2 * GeV, 0.1,
Cuts::abseta < 2.5 && Cuts::pT > 20 * GeV && Cuts::abspid == PID::ELECTRON,
Cuts::massIn(71 * GeV, 111 * GeV));
declare(zeeFinder, "Zee");
DileptonFinder zmumuFinder(91.2 * GeV, 0.1,
Cuts::abseta < 2.4 && Cuts::pT > 20 * GeV && Cuts::abspid == PID::MUON,
Cuts::massIn(71 * GeV, 111 * GeV));
declare(zmumuFinder, "Zmumu");
// Initialise and register projections
LeptonFinder ef(Cuts::abseta < 2.5 && Cuts::pT > 20 * GeV && Cuts::abspid == PID::ELECTRON, 0.1);
LeptonFinder mf(Cuts::abseta < 2.4 && Cuts::pT > 20 * GeV && Cuts::abspid == PID::MUON, 0.1);
declare(ef, "Electrons");
declare(mf, "Muons");
declare(MissingMom(), "MET");
book(_h_ZpT, "d03-x01-y01");
book(_h_Njet, "d04-x01-y01");
book(_h_JpT, "d05-x01-y01");
MSG_WARNING("LIMITED VALIDITY - check info file for details!");
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Find Z -> l+ l-
const DileptonFinder& zeeFS = apply<DileptonFinder>(event, "Zee");
const DileptonFinder& zmumuFS = apply<DileptonFinder>(event, "Zmumu");
const Particles zlls = zeeFS.bosons() + zmumuFS.bosons();
if (zlls.empty()) vetoEvent;
// Require some MET
const MissingMomentum& mm = apply<MissingMom>(event, "MET");
const P4& pmiss = mm.missingMom();
if (pmiss.pT() < 30 * GeV) vetoEvent;
// Next find the W's
const Particles& es = apply<LeptonFinder>(event, "Electrons").particles();
const Particles es_mtfilt = select(es, [&](const Particle& e) {
return inRange(mT(e, pmiss), 60 * GeV, 100 * GeV);
});
const int iefound = closestMatchIndex(es_mtfilt, pmiss, Kin::mass, 80.4 * GeV);
const Particles& ms = apply<LeptonFinder>(event, "Muons").particles();
const Particles ms_mtfilt = select(ms, [&](const Particle& m) {
return inRange(mT(m, pmiss), 60 * GeV, 100 * GeV);
});
const int imfound = closestMatchIndex(ms_mtfilt, pmiss, Kin::mass, 80.4 * GeV);
// Build a combined list of pseudo-W's
Particles wls;
wls.reserve(2);
if (iefound >= 0)
wls.push_back(
Particle(copysign(PID::WBOSON, es_mtfilt[iefound].pid()), es_mtfilt[iefound].mom() + pmiss));
if (imfound >= 0)
wls.push_back(
Particle(copysign(PID::WBOSON, ms_mtfilt[imfound].pid()), ms_mtfilt[imfound].mom() + pmiss));
if (wls.empty()) vetoEvent;
// If more than one Z candidate, use the one with Mll nearest to MZ
/// @todo Can now use the closestMassIndex functions
const Particles zlls_mz = sortBy(zlls, [](const Particle& a, const Particle& b) {
return fabs(a.mass() - 91.2 * GeV) < fabs(b.mass() - 91.2 * GeV);
});
const Particle& Z = zlls_mz.front();
// const bool isZee = any(Z.constituents(), hasAbsPID(PID::ELECTRON));
// If more than one W candidate, use the one with Mlv nearest to MW
/// @todo Can now use the closestMassIndex functions
const Particles wls_mw = sortBy(wls, [](const Particle& a, const Particle& b) {
return fabs(a.mass() - 80.4 * GeV) < fabs(b.mass() - 80.4 * GeV);
});
const Particle& W = wls_mw.front();
// const bool isWe = any(W.constituents(), hasAbsPID(PID::ELECTRON));
// Isolate W and Z charged leptons from each other
for (const Particle& lw : W.constituents()) {
if (lw.charge3() == 0) continue;
for (const Particle& lz : Z.constituents()) {
if (deltaR(lw, lz) < 0.1) vetoEvent;
}
}
// Fill Z pT histogram
_h_ZpT->fill(Z.pT() / GeV);
// Isolate jets from W and Z charged leptons
const Particles wzleps = select(W.constituents() + Z.constituents(), isChargedLepton);
const Jets& jets = apply<FastJets>("Jets", event).jetsByPt(Cuts::pT > 30 * GeV and Cuts::abseta < 2.5);
const Jets isojets = discardIfAnyDeltaRLess(jets, wzleps, 0.5);
// Fill jet histograms
_h_Njet->fill(isojets.size());
if (!isojets.empty()) _h_JpT->fill(isojets[0].pT() / GeV);
}
/// Normalise histograms etc., after the run
void finalize() {
// Total cross-section is corrected for BR(W->lnu), BR(Z->ll), leptonic-tau fraction f_tau = 6.5-7.6%,
// and unpublished detector/acceptance signal efficiencies epsilon_sig. Fix to published value: valid for shape comparison only
const double xsec8tev = 24.09; // picobarn;
normalize(_h_ZpT, xsec8tev);
normalize(_h_Njet, xsec8tev);
normalize(_h_JpT, xsec8tev);
}
private:
/// Histogram
Histo1DPtr _h_ZpT, _h_JpT;
BinnedHistoPtr<int> _h_Njet;
};
RIVET_DECLARE_PLUGIN(CMS_2016_I1487288);
} ```